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1 November 2009 Lyme Borreliosis in Canada: Biological Diversity and Diagnostic Complexity from an Entomological Perspective
Janet L.H. Sperling, Felix A.H. Sperling
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Lyme borreliosis (LB), also known as Lyme disease, is emerging as a serious tick-borne illness across Canada. More than three decades of research on LB in North America and Europe have provided a large, complex body of research involving well-documented difficulties at several levels. However, entomologists are well situated to contribute to resolving some of these challenges. The central pathogen in LB, the spirochete Borrelia burgdorferi Johnson et al., includes numerous genospecies and strains that are associated with different disease symptoms and distributions. The primary vectors of LB are ticks of various Ixodes Latreille species (Acari: Ixodida: Ixodidae), but questions linger concerning the status of a number of other arthropods that may be infected with B. burgdorferi but do not transmit it biologically. A variety of vertebrates may serve as reservoirs for LB, but differences in their ability to transmit LB are not well understood at the community level. Persistent cystic forms of and immune-system evasion by B. burgdorferi contribute to extraordinary challenges in diagnosing LB. Multiple trade-offs constrain the effectiveness of assays like ELISA, Western blot, polymerase chain reaction, and microscopic visualization of the spirochetes. Consequently, opportunities abound for entomologists to contribute to documenting the diversity of the players and their interactions in this devilishly complex disease.


Lyme borreliosis (LB) is a potentially debilitating illness that is typically vectored by ixodid ticks (Acari: Ixodida: Ixodidae) and caused by infection by the spirochete Borrelia burgdorferi Johnson et al. or other closely related species of Borrelia Swellengrebel. While the disease is also known as Lyme disease, the term Lyme borreliosis is becoming increasingly prominent internationally, to emphasize the causative organism (Gray et al. 2002). It has become the most common disease vectored by arthropods in the United States of America (USA), with the majority of cases occurring in the northeastern and north-central regions. In 2005, a total of 12 914 cases were reported among the 56 million inhabitants of the 10 states that border eastern and central Canadian provinces, and the incidence of LB has more than doubled since it became nationally notifiable in the USA in 1991 (Centers for Disease Control and Prevention (CDC) 2007). In contrast, although most of the 32 million inhabitants of Canada lived within 150 km of the United States border in 2005, fewer than 50 cases of LB per year were diagnosed in humans by Canadian laboratories and approximately half of these were associated with travel to areas outside Canada (Charron and Sockett 2005).

In Canada, accurate LB statistics have been difficult to obtain because the disease is not yet nationally notifiable (Ogden et al. 2008a; Canadian Paediatric Society Infectious Diseases and Immunization Committee (CPS) 2009). Nonetheless, B. burgdorferi has now been recognized in every province (Table 1). Recent passive surveillance from Manitoba eastward has shown that 12.5% of sampled specimens of the tick vector Ixodes scapularis Say were infected with B. burgdorferi, including 10% of those collected on humans (Ogden et al. 2006). Infected ticks are not a new phenomenon in Canada; soon after the original description of B. burgdorferi, Lindsay et al. (1991) reported a 58% prevalence of B. burgdorferi in adult Ixodes Latreille at Long Point, Ontario.

LB has been recognized by the Public Health Agency of Canada as becoming increasingly important for Canadians (Ogden et al. 2008a, 2008d). Even so, some infectious-diseases specialists disagree, noting that the disease is rare and reports of endemic cases have not increased in Canada during the past two decades (CPS 2009). In the USA, controversy over the diagnosis and treatment of LB has resulted in an increasing polarization of views, with some doctors interpreting it as a serious illness with long-term sequelae (e.g., Fallon et al. 2008; Stricker and Johnson 2008; Cameron 2009) and others viewing it as a faddish ailment used by patients to displace the less socially palatable medical explanation of psychiatric difficulties (Sigal and Hassett 2002; Hassett et al. 2008). Ballantyne (2008) concluded that such controversies can only be resolved with further research. Limitations in the sensitivity and specificity of blood tests across the genetic diversity of Borrelia species, an incomplete understanding of their immune-system evasion and persistence, variation in the degree of human immunity, and complications due to co-infections by other disease-causing microorganisms all contribute to the complexity of the interactions between the spirochetes, their vectors, and their vertebrate hosts. Even in Connecticut, where LB was first described and incidence is still very high, treatment has been sufficiently controversial that the Connecticut General Assembly recently passed legislation protecting doctors from disciplinary action for prescribing long-term treatment with antibiotics (Connecticut General Assembly 2009).

Table 1.

Reports of Lyme borreliosis (LB) and Ixodes ticks in Canada.


Entomologists are no strangers to the complexity that accompanies diversity, and are well positioned to make positive contributions to resolving some of the controversies that surround LB. In fact, entomologists have a vested interest in LB because many are potentially exposed to infection during field-work (Piacentino and Schwartz 2002; Vázquez et al. 2008) and yet are also aware of the potential for entomophobic hysteria. Furthermore, entomologists in Canada have an opportunity to make a fresh start, taking advantage of the currently low profile of the disease in Canada but building on the large volume of recent scientific studies from the USA and Europe. The purpose of this review is to explore the scientific, peer-reviewed research on LB that is relevant to Canada, with particular focus on biological and diagnostic factors that contribute to making this disease so challenging.

The natural history and ecology of LB

Diversity of Borrelia species and delimitation of B. burgdorferi

After investigating bacteria in ticks that were implicated in a cluster of juvenile arthritis cases from Old Lyme, Connecticut (41°19′N, 72°20′W), Burgdorfer et al. (1982) proposed that a spirochete was the etiologic agent of this illness. European researchers isolated a morphologically and immunologically similar spirochete from the skin and cerebrospinal fluid of a patient suffering from Bannwarth's syndrome (Pfister et al. 1984). The spirochete was formally named B. burgdorferi by Johnson et al. (1984) and later shown to include three distinct phyletic groups (Welsh et al. 1992). These three groups of strains, referred to as B. burgdorferi sensu stricto (s.s.), B. garinii Baranton et al., and B. afzelii Canica et al., were associated with differences in clinical symptoms within a broad definition of LB (Lebech et al. 1994). Borrelia burgdorferi tends to produce arthritic symptoms, B. garinii tends to infect neural tissue, and B. afzelii may persist in the skin (Terekhova et al. 2006; Tilly et al. 2008; Craig-Mylius et al. 2009; Hildenbrand et al. 2009; Kudryashev et al. 2009).

Rudenko et al. (2009) have now described Borrelia carolinensis from the southeastern USA as the 14th species of the B. burgdorferi sensu lato (s.l.) complex. The members of this species complex vary in host/vector associations, pathogenicity, and distribution, and have now been recorded in many areas where they were not previously thought to occur (Rudenko et al. 2009). In North America, Lyme-like borreliosis may also be caused by B. lonestari Armstrong et al. (Stromdahl et al. 2003) and B. bissettii Postic et al (Schneider et al. 2008), both of which occur widely on the continent. A Colorado isolate of B. bissettii has been shown to be pathogenic to mice, but an isolate from British Columbia was not (Schneider et al. 2008). Another species, B. californiensis Postic et al., is of unknown pathogenicity and has so far only been documented from California, where it is primarily associated with the California kangaroo rat, Dipodomys californicus Merriam (Postic et al. 2007).

Outside the B. burgdorferi s.l. complex, other Borrelia species can cause relapsing fever, with B. hermsii (Davis) vectored by argasid ticks (Ixodida: Argasidae) and occurring in British Columbia, Montana, and south through the Rocky Mountains (Schwan et al. 2007), and B. recurrent is (Lebert) vectored by the human body louse, Pediculus humanus L. (Anoplura: Pediculidae), in several widely separated Third World countries (Cutler et al. 1997). Borrelia recurrentis infection may occur either by crushing infected lice into broken skin or by contact with infected louse feces (Houhamdi and Raoult 2005). Difficulties in diagnosing Borrelia spp. have been reviewed by Exner (2004).

Unexpectedly large genetic diversity has also been found within B. burgdorferi s.s. For example, nine distinct clonal lineages were found at one field site in the northeastern USA (Bunikis et al. 2004). Differences in fitness between two of these genotypes, one isolated from blood and the other from skin, were studied in mice by Hanincová et al. (2008). The blood isolate retained its infectivity to xenodiagnostic ticks, whereas the skin isolate did not, suggesting partial diversification into more specialized subtypes in North America. Additional research in North America and Europe has shown further diversity in B. burgdorferi s.s.; at least 12 distinct sequence types defined by DNA sequence differences in outer-surface protein C (OspC) coexist in the northeastern USA and at least 17 OspC types are found across the USA and Europe (Qiu et al. 2008). OspC-A genotypes are associated with a highly virulent clonal group that has a wide distribution, suggesting recent migration of OspC-A genes into North America from Europe within the past few hundred years (Qiu et al. 2008). Interestingly, the OspC-A sequence at the OspC locus characterizes isolate B31, which was explicitly identified as the “type strain” in the original description of B. burgdorferi (Johnson et al. 1984). Most of the genome of B31 has subsequently been sequenced by Casjens et al. (2000).

Based on multilocus sequences for several slow-evolving housekeeping genes (MLSTs), Margos et al. (2008) agreed with Qiu et al. (2008) about the European origin of B. burgdorferi; however, they contended that B. burgdorferi has existed in North American refugia for much longer, in the order of millions of years. Although Margos et al. (2008) documented substantial discordance in topology as well as evolutionary processes between their concatenated MLST markers compared with the OspC locus, they did not consider whether recent introgression and hybridization of genes introduced from Europe may have contributed to the virulence of LB via hybridization. In other words, differences between MLSTs and OspC topology may reflect legitimately distinct biological processes in which housekeeping genes characterize a portion of the genome that has remained geographically stable, whereas OspC genes show signs of strong selection and recent trans-Atlantic gene flow. If so, this would mean that MLSTs may not unambiguously genotype B. burgdorferi samples or establish their evolutionary relationships and population structure at different levels, as was maintained by Margos et al. (2008).

Although intellectually fascinating, the complexity of B. burgdorferi s.l. has provoked spirited disagreement. Even the delimitation of LB is contentious. One school of thought is represented by the Infectious Diseases Society of America (Wormser et al. 2006, 2007) and relies on narrowly focused serology that is commonly applied in Canada using commercial diagnostic kits such as MarDx (Canadian Public Health Laboratory Network (CPHLN) 2007), which were developed using the B31 strain of B. burgdorferi s.s. In contrast, the International Lyme and Associated Diseases Society defines LB more broadly as infection with B. burgdorferi s.l., which may be confounded with associated co-infections (Cameron et al. 2004). A small minority of practitioners even prefer to describe LB as a disease that is primarily a polymicrobial infection, emphasizing synergies of co-infections and host factors rather than the diversity of Borrelia spp. to explain the complex and notoriously variable clinical presentations of LB (Owen 2006). In common with other spirochetal diseases, LB has a wide spectrum of clinical symptoms that usually occur in successive stages (Miklossy 2008; Hildenbrand et al. 2009), and this diversity of symptoms, whether they are concurrent or successive, certainly contribute to the challenge of determining which of these symptoms are due to B. burgdorferi.

Vector incidence and distribution

Borrelia burgdorferi is almost exclusively vectored by Ixodes ticks throughout its temperate Northern Hemisphere distribution (Eisen and Lane 2002). In British Columbia the primary vector is I. pacificus Cooley and Kohls, whereas across central and eastern Canada it is I. scapularis; together these two tick species are believed to be responsible for almost all human LB infections in Canada (Ogden et al. 2008d).

There are various methods of sampling ticks for study. Probably the most common is flagging (or dragging), which usually involves dragging a flannel sheet about 1 m2 in area lightly against vegetation for a specific amount of time before inspecting it visually for adhering ticks (e.g., Faulde and Robbins 2008; Ogden et al .2008d; Scott et al. 2008). Alternatively, humans wearing protective clothing may be inspected for attached ticks (Lane et al. 2004; Faulde and Robbins 2008). These techniques suffer from the disadvantages that sampling takes place over a relatively short time period and is subject to weather conditions (Gray 1985).

Longer term sampling may be accomplished using caged sentinel animals (Burkot et al. 2001) or carbon dioxide traps (Gray 1985) but is problematic because I. scapularis has very limited horizontal movement (Falco and Fish 1991). Livetrapped animals can be inspected visually for ticks (Ogden et al., 2008c; Salkeld et al. 2008) or their cages can be suspended over water into which the ticks fall (Ginsberg et al. 2005). Lane and Loye (1991) reported that visual inspection detected as few as 45% of the number of I. pacificus that were found using drop-off collection. Birds can be a source of ticks during banding (Scott et al. 2001; Morshed et al. 2005; Smith et al. 2006), as can deer killed by hunters (Lindsay et al. 1999b; Shariat et al. 2007). Passive surveillance may involve taking advantage of ticks removed in medical or veterinary clinics (Ogden et al. 2006, 2008d). A flaw of passive sampling is that the nymph is the tick life stage most likely to transmit disease to humans (Mather et al. 1996), but most ticks submitted as a result of passive surveillance are adult females, which are more easily detected (Morshed et al. 2006; Ogden et al. 2006).

The basic phenology of Ixodes ticks in Canada can be described relatively simply (Fig. 1) but there is substantial variation in the basic pattern within and between regions. An established population at Long Point in southern Ontario has received the best documentation to date (Lindsay et al. 1999a, 1999b). Larval activity in this area was lengthy, with weak peaks in mid to late June and mid-August (Lindsay et al. 1999a). On the other hand, nymphs were most abundant during a narrower time range, in June and July (Lindsay et al. 1999a), and adult activity was distinctly bimodal, with peaks in April and October (Lindsay et al. 1999b). The bimodal questing activity of adult I. scapularis in Ontario has been confirmed by Morshed et al. (2006), and in Manitoba, peak activity of adult I. scapularis occurs between September and November, with a second peak from April to June (Galloway 2002). Elsewhere in Canada the phenology of Ixodes may vary depending on local conditions; however, detailed studies are not generally available. In California, adult I. pacificus have a bimodal activity pattern, with peak activity in both March and December and nymphs occurring between April and August (Clover and Lane 1995).

Fig. 1.

Typical life cycle of the blacklegged tick, Ixodes scapularis, and associated infection by Borrelia burgdorferi in Canada, showing the succession of immunological and environmental challenges to spirochetes (broken lines and “wiggles”) as they cope with tick searches for hosts, successive tick life stages, variation in blood-meal sources, and transmission to and from vertebrate hosts. Phenology is largely taken from Lindsay et al. (1999a, 1999b) and Galloway (2002), although the cycle may be extended for 1 or more years if ticks are unable to find food in any given year.


In agreement with Lindsay et al.'s (1999b) findings for southern Ontario, long duration and weak bimodality are also evident in the activity of larval I. scapularis from both the northeast and Upper Midwest of the USA (Gatewood et al. 2009), although the authors chose to fit a unimodal curve to their larval-occurrence data. In contrast, the seasonal activity of nymphs was explicitly recognized as bimodal, and the variation in size of the two nymphal-activity peaks was interpreted as the result of variation in the number of larvae that hatch in midsummer and then may or may not be able to feed before overwintering (Gatewood et al. 2009). However, it is plausible that adult phenology also contributes to the biomodality of both larval and nymphal activity. Extended larval activity may be due to the overlap of two cohorts: larvae hatching from eggs laid early in spring by females that had fed in the fall and overwintered, and those resulting from females that fed in spring and laid eggs somewhat later. As Killilea et al. (2008) have emphasized, there is a strong need for standardized sampling of all life stages of ticks across broad geographic regions.

Primary tick identification guides that are likely to be useful in Canada include Gregson (1956), Keirans and Clifford (1978), Furman and Loomis (1984), Durden and Keirans (1996), and Web sites such as Ticks of Canada (Canadian Lyme Disease Foundation 2009) and Anderson and Harrington (2009). Lindquist et al. (1999) produced couplets that augment the keys of Gregson (1956), Keirans and Clifford (1978), and Durden and Keirans (1996).

Established populations of I. scapularis have been well documented in localized areas of Nova Scotia, Ontario, and Manitoba (Ogden et al. 2008a). Populations of I. pacificus have been established for at least a century in southern British Columbia (Gregson 1956). The dispersal and population structure of I. pacificus are still poorly understood, but work based on both allozymes and mtDNA has shown patterns of high local genetic diversity and locus-specific isolation or selection in localities ranging from West Vancouver, British Columbia, to southern California and Utah (Kain et al. 1997, 1999). Ixodes vectors can be spread by migratory birds across most of Canada (Scott et al. 2001; Morshed et al. 2005; Ogden et al. 2008c), which means that sporadic cases of LB can occur throughout Canada and transient populations of Ixodes ticks could establish in suitable localized habitats. Because I. scapularis and I. pacificus commonly feed on deer and other vertebrates that live in woodlands, increases in tick numbers can result from restoration of woodlands, especially in semi-urban areas, where hunting of deer is discouraged (Killilea et al. 2008). Changes in the distribution of ticks as a result of climate change are predicted to be disproportionately serious in Canada, with consequent increases in cases of LB (Ogden et al. 2006, 2008a, 2008c, 2008b).

Other confirmed vectors of B. burgdorferi that are known to range into Canada include Ixodes angustus Neumann, I. dentatus Marx, I. jellisoni Cooley and Kohls, I. muris Bishopp and Smith, and I. spinipalpis Hadwen and Nuttall (Gregson 1956; Eisen and Lane 2002). Older literature that lists I. dammini Spielman et al. as a vector of B. burdorfieri (e.g., Lindsay et al. 1991) refers to I. scapularis; these two species are now considered conspecific (Wesson et al. 1993). Ixodes cookei Packard is not considered to be a competent vector of B. burgdorferi (Barker et al. 1993), although B. burgdorferi is documented from a specimen of I. cookei and its dog host in central Alberta (Fernando et al. 2008). Borrelia garinii, the most neurotropic of the European forms of LB, has been found in I. uriae White on seabirds in Newfoundland (Smith et al. 2006). In general, most Ixodes ticks in Canada appear to be competent, although not necessarily efficient, vectors of B. burgdorferi (Eisen and Lane 2002). Ixodes gregsoni has been newly described from mustelids in Canada Lindquist et al. (1999), but is unlikely to have much of an effect on transmission of B. burgdorferi because mustelids are poor reservoirs (LoGiudice et al. 2003). A number of ticks can acquire B. burgdorferi infections but are considered incompetent because they are unable to pass the infection on to the next host; these include Amblyomma americanum (L.), Haemaphysalis leporispalustris Packard, all species of Dermacentor C.L. Koch, and a few species of Ixodes (Eisen and Lane 2002). Vector competence is defined as the ability to (i) acquire spirochetes when feeding on an infected host, then (ii) pass them between tick life stages, and subsequently (iii) pass the infection to a susceptible host while feeding (Eisen and Lane 2002). Transmission of Borrelia from younger to older tick life stages is well established and such trans-stadial transmission is important because ticks generally feed on only one individual host per tick life stage (Oliver 1989). Less is known about the prevalence and importance of infection passed to larvae from adult females via the egg stage (Eisen and Lane 2002), although such transovarial infection may be important in Europe (Kurtenbach et al. 1995). For all forms of transmission, however, it is difficult to distinguish experimentally between complete incompetence and rare vectoring because of low tick infectivity (Kahl et al. 2002). The B. burgdorferi-vectoring competence of ticks is distinguished from mechanical transmission, where pathogens are not passed via the normal tick salivary secretions but are introduced past broken skin by a mechanism such as pathogens clinging to the mouthparts (an unlikely scenario considering the sensitivity of Borrelia to oxygen; Barbour and Hayes 1986) or, more plausibly, crushing a tick into a wound in the course of attempted removal. For a tick-borne proteobacterium, Anaplasma Theiler, in cattle, mechanical vectoring via the mouthparts of biting flies is approximately two orders of magnitude less efficient than biological vectoring (Scoles et al. 2005). However, the efficiency of mechanical vectoring of Borrelia and its role in human illness are not known. Until recently, autoinoculation by crushing lice into wounds was thought to be the only way that B. recurrentis was transmitted (Houhamdi and Raoult 2005).

In addition to tick species, mosquitoes (Diptera: Culicidae), tabanid flies (Diptera: Tabanidae), and fleas (Siphonaptera) are known to harbor a competent vector B. burgdorferi but none has been shown to be competent as defined by Eisen and Lane (2002). In mosquitoes, for example, 7%–8% of adult female Aedes Meigen in Connecticut (Magnarelli et al. 1986) and 1.7% of Culex pipiens (L.) in Poland carried B. burgdorferi (Kosik-Bogacka et al. 2007). Furthermore, transmission between mosquito life stages is suggested by the occurrence of Borrelia in 1.6% of larval Culex L. in the Czech Republic (Zákovská et al. 2002) and 3.2% of larval and 1.6% of pupal C. pipiens in Poland (Kosik-Bogacka et al. 2007). Mites may also contain B. burgdorferi (Zakovska et al. 2008), but no surveyed spiders have been found to harbor Borrelia (Suffridge et al. 1999).

There are anecdotal reports of LB transmitted by vectors other than ticks in Canada (Doby et al. 1987) and the USA (e.g., Luger 1990). These are unsupported by any of the evidence normally required to demonstrate competence or even mechanical vectoring. Nonetheless, although statements such as “fleas, flies, and mosquitoes are not vectors for Lyme disease” (Bratton et al. 2008) are common in the medical literature, it is conceivable that the detailed documentation of transmission by tick vectors has over-shadowed occasional mechanical transmission by secondary vectors. Eisen and Lane (2002) state, “Although insects may prove incompetent to serve as vectors for B. burgdorferi s.l., the possibility of occasional mechanical transmission should not be discounted”. Further study is clearly needed.

Diversity and dynamics of reservoir hosts

The primary reservoir host of LB in North America has long been assumed to be white-footed mice (Levine et al. 1985), although recent research in the northeastern USA shows that two shrew species are each at least as likely as white-footed mice to be a potential source of infection for humans in some locations (Brisson et al. 2008). On the west coast of North America, infection rates demonstrate that squirrels are highly competent reservoirs and their infection rates correlate closely with rates of human infection (Salkeld et al. 2008). Major described hosts of B. burgdorferi that interact with humans include white-footed mice, chipmunks, squirrels, wood rats, and shrews (Killilea et al. 2008).

Some animals that act as common hosts for tick vectors, most notably deer in Europe and North America (Kurtenbach et al. 1998; Ullmann et al. 2003) and lizards in California (Lane 1990; Giery and Ostfeld 2007), are able to clear infection by B. burgdorferi and thereby may actively contribute to reducing rates of infection with B. burgdorferi. Thus, high deer densities could have both a positive and a negative influence on the zoonotic cycle of LB by allowing tick populations to be high while reducing rates of Borrelia infection in ticks if deer are the primary intermediate host between rodents, such as shrews, and humans. However, a recent report from Tennessee shows that 33% of winter ticks, Dermacentor albipictus (Packard), collected from white-tailed deer were positive for B. burgdorferi or B. lonestari (Shariat et al. 2007). The observation that Borrelia was not cleared from ticks feeding on these deer suggests that in some areas deer may still be significant reservoir hosts. The report by Shariat et al. (2007), however, is anomalous and it remains to be shown that D. albipictus could vector Borrelia. Lizards are also variable in their ability to clear B. burgdorferi infection (Clark et al. 2005) and are not universal in their incompetence as reservoir hosts (Giery and Ostfeld 2007).

Since birds, including migratory song birds that nest in urban habitats, are important for long-distance dispersal of ticks (Morshed et al. 2005; Ogden et al. 2008c; Scott et al. 2001) and some are important reservoirs for B. burgdorferi (Ginsberg et al. 2005), they can play an important role in peridomestic exposure to LB (Ginsberg et al. 2005).

In addition to variation in the strains of Borrelia that they tend to carry, reservoir animals exhibit differing symptoms of infection. For example, mice, commonly used as models for human infection, do not develop the characteristic bull's-eye rash or exhibit clear neurological manifestations of LB, although they are excellent models for the arthritis form of LB (Yrjänäinen et al. 2007). This may explain the greater attention paid to the arthritis form of LB, for which an excellent animal model exists, than to the neurological form, where animal models are more problematic (Nardelli et al. 2008; Rupprecht et al. 2008).

Rates of infection of I. pacificus by B. burgdorferi are considered low in British Columbia (Ogden et al. 2008d) and reported as being less than 1% across the province (British Columbia Ministry of Health 2008). Charron and Sockett (2005) have speculated that this is due to the preference for lizard hosts shown by I. pacificus in the nymphal stage, presumably based on the borreliacidal properties of lizard blood demonstrated in California (Lane 1990; Slowik and Lane 2009). However the significance of such an interaction remains to be demonstrated in British Columbia, where lizards, being at the extreme northern edge of their ranges, are at much lower density. In British Columbia, the effect of climate change and the importance of patchiness in the distribution of B. burgdorferi and infected hosts are currently unpredictable (Ogden et al. 2008b).

Risk of human exposure to LB

The risk of human exposure to LB is related to numerous factors, such as the identity of ticks, the particular Borrelia strain, previous hosts, local ecological interactions, or human behavior (Horobik et al. 2006). Human behaviors that bring people into contact with ticks include sitting on logs, gathering wood, leaning against trees, walking in natural areas, and stirring or sitting on leaf litter (Lane et al. 2004). Even when considerable personal protection measures are taken by highly motivated entomologists, potentially infected ticks have been removed up to 2 days later, demonstrating that the risk of exposure to LB is still significant (Lane et al. 2004; Vázquez et al. 2008). Forest fragmentation may increase the risk of LB through loss of predators from smaller patches and a consequent increase in the abundance of small rodents, leading to higher densities of infected nymphal ticks (Allan et al. 2003). Also, highly diverse communities of vertebrates are less likely to bring infected nymphs into contact with humans, owing to “dilution effects” (LoGiudice et al. 2003). The dilution effect hypothesis states that when there are multiple vertebrate hosts for ticks, and these hosts differ in how well they clear infection but do not differ in resistance to ticks, then B. burgdorferi will no longer be transmitted as efficiently as when only the most susceptible hosts are infected. A number of other factors are also likely to influence the distribution and infection rates of ticks and there is a clear need for tick occurrence to be documented in a more standardized manner at multiple spatial and temporal scales (Killilea et al. 2008).

In the USA, the number of infected nymphs of I. scapularis and I. pacificus correlates with reported human disease more than does the incidence of adult ticks, and therefore nymphs are the life stage most commonly associated with disease transmission (Clover and Lane 1995; Mather et al. 1996; CDC 2007). The small size of Ixodes tick nymphs and their rapid feeding rate compared with that of adults are considered to be factors in increasing spirochete transmission to humans by nymphs (Clover and Lane 1995). Moreover, if nymphs are more likely than larvae to feed on hosts with borreliacidal blood, such as lizards or potentially even deer, this may also contribute to reducing rates of disease transmission by adult ticks relative to earlier life stages. Regardless of the underlying mechanism, it is important to survey nymphal ticks as well as adults to accurately assess disease incidence.

In regions of Canada where ticks are not endemic, however, the role of adults in vectoring should be clarified because, in such regions, a relatively high proportion of adults may have fed on migratory birds rather than on mammals when they were in the nymphal stage (Morshed et al. 2006). Birds from near Long Island, New York, have been demonstrated to be competent reservoirs for Borrelia, with wild-caught robins infecting 16% of larval ticks placed on them, whereas robins that were previously infected by nymphal ticks in the laboratory passed that infection on to 82% of larvae that subsequently fed on them (Ginsberg et al. 2005). Although it is unclear whether similar infection rates apply to adult ticks that fed on birds as nymphs, it remains to be seen whether the adult stage of ticks may have greater importance in disease transmission in regions of Canada where Ixodes spp. are primarily derived from birds.

Physiological processes

Gene regulation and transmission dynamics

For B. burgdorferi to be transmitted from a cold-blooded tick vector to a warm-blooded host, it must regulate its gene expression in a complex and as yet incompletely understood manner. Models of gene regulation range from simple ones based solely on temperature and pH (Schwan et al. 1995) to a new paradigm suggested by Stevenson et al. (2006), who cautioned that the effects of temperature and pH may not predict the in vivo expression of genes. The synthesis of each of five different lipoproteins is controlled in a distinct manner, in some cases opposite to that predicted from temperature and pH effects in vitro (Stevenson et al. 2006).

Studies of the transmission dynamics of B. burgdorferi in I. scapularis indicate that the risk of transmission of strain B31 by a single bite from an infected tick is about 2% and that the risk increases with the length of time that the tick is attached (Hojgaard et al. 2008). When a tick first attaches, spirochetes are still found in the midgut and are producing outer-surface protein A (OspA), which helps spirochetes adhere to a midgut protein, TROPSA. When feeding begins, the spirochetes are exposed to warm mammalian blood and lowered pH, and OspA is downregulated while OspC is upregulated. Spirochetes then migrate from the midgut to the salivary gland and transmission to the vertebrate host can be achieved (e.g., Hojgaard et al. 2008). This delay in transmission explains why transmission is reduced when ticks are removed within 24 h of attachment (Hojgaard et al. 2008). In Europe, transmission of B. burgdorferi s.s. and B. afzelii by I. ricinus occurs in less than 24 h, but the risk of transmission still increases over time (Kahl et al. 1998; Crippa et al. 2002). In a further complication of the host—tick—pathogen interaction, B. burgdorferi s.l. is able to increase expression of an Ixodes salivary protein, Salp 15, to protect against complement-mediated killing of Borrelia by the host's innate immune system (Ramamoorthi et al. 2005). This protective effect was greater when the vector was I. ricinus rather than I. scapularis (Schuijt et al. 2008). The early expression of ospC appears to be essential for B. burgdorferi to escape innate immunity and disseminate in the host (Gilbert et al. 2007), and yet persistent infection of the host is only possible when ospC is downregulated after infection because acquired antibodies to OspC allow the spirochetes to be cleared (Tilly et al. 2007). Current understanding of the interactions of tick saliva and B. burgdorferi is discussed in Anderson and Valenzuela (2007).

Even though vectoring by ticks is the most likely way to contract LB (and gene regulation of outer-surface proteins on Borrelia as well as increased expression of Salp 15 in the tick vector will increase the probability of infection of the vertebrate host), there is nonetheless some evidence that contact transmission of B. burgdorferi can also occur without a vector. Burgess and Patrican (1987) have shown that deer mice can be infected orally by ingesting saline containing B. burgdorferi and that these mice can in turn infect ticks that feed on them. Despite an explicit search of the LB literature, it is not apparent that any studies have addressed whether Borrelia can be transmitted to vertebrate hosts that eat infected ticks or, for that matter, by contact between hosts via body fluids such as urine or sperm. However, Kurtenbach et al. (1994) have demonstrated differences in the antibody responses of various mouse species infected by needle inoculation versus tick bites. Tick-infected mice did not express antibodies to OspA or outer-surface protein B (OspB) early in the infection, whereas intradermally injected mice did (Kurtenbach et al. 1994). However, infection proceeded in both groups; in fact, intradermal inoculation is commonly used to ensure that a controlled quantity of pathogen is transferred in studies of LB (e.g., Hodzic et al. 2008). Recent research has shown that both OspA and OspB are involved in binding to the tick gut, so the results of Kurtenbach et al.'s (1994) study are counter to what would be expected. OspB-deficient B. burgdorferi is infectious and pathogenic in mice but is unable to survive in Ixodes (Neelakanta et al. 2007).

Careful and prompt removal of attached ticks is nonetheless important in reducing the probability of transmission of B. burgdorferi (Hojgaard et al. 2008). The preferred method is to grasp the mouthparts firmly with fine-pointed forceps and pull them straight out in a single action without twisting. This should reduce the risk of regurgitation of gut contents (Gammons and Salam 2002). An alternative method for removing attached ticks is the “straw and knot method” of Murakami (2009): a drinking straw is used to guide a thread to the base of the mouthparts, allowing the tick be pulled out in a single motion. Any remaining mouthparts should be excised and the area cleaned with antiseptic solution. Removal of the cement plug attaching the mouthparts to the wound may be important because B. burgdorferi can be present in it (Alekseev et al. 1995).

Persistent infection

Borrelia spp. are capable of persistent infection, and such persistence is the norm in mice, rats, hamsters, dogs, and monkeys (Barthold 2000; Straubinger 2000; Summers et al. 2005; Hodzic et al. 2008). Persistence in reservoir hosts can be interpreted as an evolutionarily shaped survival strategy linked to the asynchronous phenology of the tick vectors (Kurtenbach et al. 2006). Although natural infections are less controlled and defined, there is strong evidence that they persist in humans also (Oksi et al. 1999; Breier et al. 2001; Miklossy et al. 2004, 2008; Hunfeld et al. 2005). Immune evasion has been extensively documented in Borrelia (Liang et al. 2002; Bankhead and Chaconas 2007; Rupprecht et al. 2008; Xu et al. 2008a; Yang et al. 2009). Although B. burgdorferi is generally considered to be an extracellular pathogen, localization has been demonstrated within endothelial cells (Ma et al. 1991; Thomas et al. 1994), synovial cells (Girschick et al. 1996), and neuronal and glial cells (Livengood and Gilmore 2006; Miklossy et al. 2006). Infiltration of blood vessels, cardiac myocytes, and collagen tissues has also been demonstrated (Pachner et al. 1995), and adherence and escape of Borrelia from vasculature has recently been visualized directly by Moriarty et al. (2008). Sequestration and physical protection from the immune system in the extracellular matrix have been reviewed by Cabello et al. (2007) and Rupprecht et al. (2008).

When exposed to unfavorable conditions such as osmotic and heat shock, B. burgdorferi produces atypical forms (e.g., Brorson and Brorson 1998, 2004; Singh and Girschick 2004; Miklossy et al. 2008; Margulis et al. 2009). The extracellular and intracellular presence of these atypical forms has been demonstrated in brain tissue of humans with confirmed neuroborreliosis, and atypical forms can exist in the absence of spirochetal forms (Miklossy et al. 2008). A thickened external membrane, observed by Miklossy et al. (2008) to surround cystic forms, was reactive to anti-OspA antibody and a full characterization of other immunogenic proteins was not attempted. Thus, a full understanding of the serology of LB must include the atypical forms as well as the typical spiral forms (Miklossy et al. 2008).

Borrelia has a unique, flexible genome

Borrelia burgdorferi contains both circular and linear DNA molecules in roughly equal numbers (Rosa et al. 2005). Most replicons are linear molecules that are terminated by hairpin turns, which are unusual in bacteria and of much interest to molecular biologists (Chaconas 2005; Tourand et al. 2009). In addition to one large linear chromosome, B. burgdorferi has over 20 plasmids, the largest number so far described in any living organism (Chaconas 2005; Rosa et al. 2005) . Some of these plasmids carry crucial information for survival in tick vectors or mammalian hosts. The linear plasmid Ip28-1 is required for persistent infection with B. burgdorferi and the presence of the vls locus on this plasmid appears to be an absolute requirement for persisting infection. Antigenic variation at vlsE by recombination of cassette fragments allows a large number of antigenically distinct variants to be produced, thus facilitating avoidance of the host's immune system (Bankhead and Chaconas 2007). The genetics of B. burgdorferi has been reviewed by Rosa et al. (2005) and Tilly et al. (2008). Furthermore, Borrelia spp. are unusual in having evaded the usual limiting factor of iron availability in the host cells by using manganese for electron transport (Posey and Gherardini 2000; Ouyang et al. 2009). Typically, at the onset of infection, humans secrete lactoferrin to limit available iron and inhibit bacterial growth (Arnold et al. 1982). Borrelia burgdorferi has eliminated most of the genes that encode proteins that require iron as a cofactor, and a manganese transporter is required for virulence in B. burgdorferi (Posey and Gherardini 2000; Ouyang et al. 2009).

Immune-system selection

Antigenic variation is a common mechanism whereby pathogenic bacteria can evade the immune system. Borrelia species are the subject of intense study that has revealed at least two different ways in which they achieve such antigenic variation. For B. hermsii, recombination of vlp and vsp sequences is responsible for antigenic variation, whereas in B. burgdorferi, recombination occurs at vlsE (Norris 2006). Furthermore, variation in VlsE of B. burgdorferi is not, by itself, sufficient to achieve resistance to reinfection, and is only part of a complex system that may confine the adaptive response of the host (Bankhead and Chaconas 2007).

Immune-system selection on B. burgdorferi has received extensive study and host specialization is thought to result from negative selection mediated by the complement system of the host's innate immune system (Schroeder et al. 2009). Spirochetes that are susceptible to destruction by the complement system of a given species are lysed early in the midgut of the tick (Kurtenbach et al. 2002a). This has led to the hypothesis that the host range of a spirochete strain is restricted by the genes that encode ligands that bind to complement inhibitors (Kurtenbach et al. 2002b).

The second main component of the mammalian immune system is the adaptive immune system, which introduces nonlinear frequency-dependent fitness, leading to fluctuations in the abundance of spirochete genotypes. Balancing selection by the adaptive immune system on the ospC gene maintains spirochete diversity within local tick populations (Schroeder et al. 2009), with persistent B. burgdorferi strains being favored over “boom and bust” ones (Kurtenbach et al. 2006). In a further refinement by Gatewood et al. (2009), persistent B. burgdorferi strains were interpreted as being favored when tick seasonality is asynchronous because of climatic conditions such as the relatively small difference between summer- and winter-temperature extremes in the northeastern USA. In the Upper Midwest of the USA, in contrast, less-persistent strains are favored because greater seasonal temperature disparities are associated with more overlap in the durations of larval and nymphal activity, allowing easier transmission of B. burgdorferi strains from infected nymphs to uninfected larvae (Gatewood et al. 2009). Modeling of tick phenology has been expanded to include synchronicity with reservoir hosts and photoperiod (Ogden et al. 2006, 2008b), and it is clear that further complexity remains to be modeled.

Diagnosis and serology of LB

Initial diagnostic steps

Although all evidence indicates that ticks are necessary for infection with B. burgdorferi, the ticks themselves are often not noticed. Steere (1989) reported that only 50%–70% of people report a tick bite before being diagnosed with LB. Tick saliva is well documented as containing an anaesthetic that reduces the probability of tick detection (Ribeiro and Francischetti 2003) and, considering their small size, immature ticks are likely to have an even lower rate of detection than adults.

On the other hand, knowledge of the presence of Ixodes ticks in an area can contribute to a diagnosis of LB. For example, an erythema migrans (EM) rash is considered sufficient by itself for a diagnosis of LB, but only in geographic areas where I. scapularis or I. pacificus is established (CPS 2009). The presence of an EM rash, with its characteristic bull's-eye appearance, is not enough to justify treatment in areas of Canada where these Ixodes species are not believed to be endemic; in such cases confirmatory serology is advised before the diagnosis is given (CPS 2009). Variability in the presence and appearance of the EM rash has been extensively documented (Tibbies and Edlow 2007; Egberts et al. 2008). About 80%) of confirmed LB patients are reported to show the rash (Aguero-Rosenfeld et al. 2005; Bratton et al. 2008), and American researchers often explicitly require the EM rash to be present for a patient to be considered for enrollment in a study (e.g., Wormser et al. 2008). Of 95 children presenting with facial palsy in an area of the USA where LB is endemic who later received serological confirmation of LB, only 35 reported the rash (Nigrovic et al. 2008). In Europe, only 18% of Swedish children with confirmed neuroborreliosis reported the rash (Skogman et al. 2008).

For a serological diagnosis of LB world-wide, either an enzyme-linked immunosorbent assay (ELISA) or an immunofluorescent assay (IFA) is expected to constitute the first step of a two-step diagnosis (Aguero-Rosenfeld et al. 2005). If the ELISA or IFA is positive, the second step is a Western blot immunoassay. Both the ELISA and the IFA are designed to detect serum antibodies produced by the host against proteins of B. burgdorferi. In Canada, only a positive or equivocal ELISA is currently accepted before a Western blot, which is more specific but more expensive, can be requested (CPHLN 2007). In the USA and Europe, either an ELISA or an IFA will fulfill the first step (CDC 1995; Brouqui et al. 2004). Like an ELISA, an IFA can use antibodies to whole-cell lysates or purified antigens such as flagellin, OspC, or P39. However, interpretation of an IFA requires well-trained personnel, whereas the more frequently used ELISA is more easily automated (Aguero-Rosenfeld et al. 2005). In Canada, the sensitivity of ELISA is considered to be close to 100% for tests performed 4 weeks post tick bite (Barker and Lindsay 2000; Forward 2005; Zaretsky 2006; CPHLN 2007; CPS 2009). This contrasts with Aguero-Rosenfeld et al. (2005), whose Table 4 reports that ELISA sensitivity is always less than 50% in the acute phase of an EM rash and only about 80% in the convalescent phase after antimicrobial treatment for an EM rash or a diagnosis of LB has been obtained because of neurological involvement. Only the arthritis form of LB was associated with higher ELISA sensitivity. There is considerable debate over the sensitivity of ELISA, especially in late stages of the disease (e.g., Donta 2007; Wilson 2007; Strieker and Johnson 2008).

In laboratory diagnoses, sensitivity is defined as the percentage of people truly suffering from a disease who are identified as positive by means of an assay (Saah and Hoover 1997). This is not the same as the more commonly understood use of the term sensitivity for analyses, which refers to an assay's ability to detect a low concentration or signal in a sample (e.g., the ability of an ELISA to detect low quantities of antibodies to B. burgdorferi). Diagnostic specificity, on the other hand, is defined as the percentage of people who do not have a disease and who are identified as negative by means of an assay (Saah and Hoover 1997). High diagnostic sensitivity means that an assay produces a high rate of true positives and a low rate of false negatives. Furthermore, high diagnostic specificity means a high rate of true negatives and a low rate of false positives. Laboratory diagnosis of LB has tended to emphasize diagnostic specificity and the need to eliminate false positives, rather than high sensitivity and the elimination of false negatives (CPHLN 2007; CPS 2009). Thus, a patient may eventually be diagnosed as having LB on the basis of PCR tests, observations of spirochetes in tissue, or clinical symptoms, in spite of an earlier ELISA test that returned a negative result. Clinicians, however, are often not aware of the potential for such false negatives, especially in late disease (Donta 2002, 2003, 2007; Wilson 2007).

Because ELISA is used as a screening method in Canada (CPHLN 2007), a negative ELISA may be taken as evidence that there is no infection with Borrelia. This interpretation of ELISA has resulted in the claim that there is no valid support for the idea that LB is underdiagnosed in Canada (CPS 2009). This viewpoint contrasts with Ogden et al. (2008d), who stated that underreporting is more biologically plausible. The documented genetic diversity and biological complexity of B. burgdorferi s.l. cannot help but contribute to difficulties in detecting Borrelia with both high sensitivity and high specificity, especially when the spirochetes enter tissues, such as collagen, to which the host's immune system has limited access (Cabello et al. 2007; Miklossy et al. 2008).

Effectiveness of specific ELISA tests

Commercial ELISA kits can be based on whole-cell sonicates or more specific antigens like flagellin and C6 peptide. Currently, whole-cell sonicates of strain B31 are used in Canada for humans (CPHLN 2007), whereas C6 peptide kits (IDEXX Laboratories, Inc. 2008) are favored for dogs. The C6 peptide ELISA relies on a single peptide from the VlsE protein, a lipoprotein with an invariable region, C6, which is highly antigenic. Because the assay based on C6 peptide is different from the standard ELISA used for the same organisms, dogs may serve as sentinels for some B. burgdorferi s.l. strains that are not detected using the whole cell sonicate ELISA kits used for humans.

The use of dogs as sentinels for LB is controversial and has recently been reviewed by Fritz (2009). The C6 peptide assay is considered to allow greater specificity than earlier assays, since it is only expressed in actively infected animals (Liang et al. 1999, 2002). Although treatment of seropositive dogs is discouraged unless clinical signs are present, the use of domestic dogs to demonstrate the presence of B. burgdorferi in areas where ticks are localized may lead to an underestimate rather than an overestimate of the presence of B. burgdorferi (Fritz 2009).

Some researchers use an in-house sonicate derived from strain B31 (e.g., Steere et al. 2008), whereas others use whole-cell sonicates of N40 (e.g., Pachner et al. 2002). Wormser et al. (2008) maintained that the diversity of LB strains is unlikely to be relevant to the diagnosis of human disease provided a whole-cell sonicate is used in the ELISA. However, use of whole-cell sonicates produces a high level of background absorbance, necessitating correction for false positives and potentially reducing the detection of true positives (Lawrenz et al. 1999; Donta 2002). It has been suggested that this effect explains the low sensitivity in a serological survey of deer in Ontario (Gallivan et al. 1998). Wilske et al. (2007) recommend that because of the heterogeneity of causative agents of LB in Europe, ELISAs should be based on OspC as well as DbpA, VlsE, or C6 peptide to improve sensitivity.

Commercial ELISA kits licensed for use in the USA vary substantially in sensitivity. Aguero-Rosenfeld et al. (2005) reported ranges from 33% (EM rash) to 79% (neuroborreliosis) and 100% (Lyme arthritis). Such an ascertainment bias in favor of the arthritis form of LB may account for statements that Lyme arthritis, the original name of the disease, is the most common form of late LB in North America (Wormser et al. 2006, 2007). Furthermore, the B31 strain has been shown to cause arthritic symptoms disproportionately relative to other members of B. burgdorferi s.l. (Terekhova et al. 2006; Tilly et al. 2008; Craig-Mylius et al. 2009; Hildenbrand et al. 2009; Kudryashev et al. 2009), so it is not unexpected that serological testing based on B31 is particularly effective in detecting the arthritis form of LB.

Western blots

Western blots, also called immunoblots, use gel electrophoresis to separate proteins by size or shape, after which they are visualized by staining with antibodies specific to the target proteins and scored for presence and intensity of the banding pattern. They are generally more expensive to run than an ELISA because they are more labor-intensive and require highly trained personnel to interpret the banding patterns (Bjerrum and Heegaard 2001).

A Western blot of patient serum antibodies to LB antigens is required as the second step in a serological diagnosis of LB. In Canada, the Western blot must have at least 2 of 3 bands for immunoglobulin M (IgM) as well as at least 5 of 10 bands for immunoglobulin G (IgG) (CPHLN 2007). These criteria were established for active or previous infection and were designed to identify a banding pattern that gave high statistical specificity. Bands for IgM antibodies to both OspA and OspB and for IgG antibodies to OspB were explicitly excluded (Dressier et al. 1993), even though these bands are highly diagnostic. Because these proteins were intended as candidates for vaccine development (Fikrig et al. 1992), assays based on these bands would have been unable to distinguish between active LB and vaccination. An OspA vaccine was eventually released but withdrawn in 2002, ostensibly for economic reasons but there were suggestions that it had autoimmune effects (Rosé et al. 2001; Nigrovic and Thompson 2007; Nardelli et al. 2008).

It is generally accepted that OspC is the immunodominant protein involved in the IgM response, while decorin-binding protein A (DbpA) is the immunodominant protein in the IgG response (Jovicić et al. 2003; Wilske et al. 2007). However, Fingerle et al. (1998) demonstrated that 31% of B. burgdorferi from ticks that had been feeding on humans in southern Germany expressed OspA rather than OspC and that these B. burgdorferi were capable of causing disease in humans. Some current Western blot kits used in Canada, such as MarDx (CPHLN 2007), are based on a sonicate of strain B31. False-negative serology is considered a significant risk in neuroborreliosis unless multiple Borrelia strains are tested for (Kaiser 2000; Jovicić et al. 2003). In Europe, multiple Borrelia species are acknowledged and Western blots are interpreted differently than in North America, where B. burgdorferi s.s. is often assumed to be responsible for all human LB (CDC 1995; Robertson et al. 2000; Wormser et al. 2006, 2007; Vanousová and Hercogová 2008).

To confirm a LB diagnosis, it may be considered necessary to document conversion from IgM to IgG about 4 weeks or more after infection (Aguero-Rosenfeld et al. 2005; Wormser et al. 2006, 2007). In some people, however, seronegativity with only a cell-mediated immune response is possible (Singh and Girschick 2004). In addition, detection of antibodies that are tied up in complexes would be missed by standard tests that rely on free antibodies (Singh and Girschick 2004; Holl-Wieden et al. 2007).

Antigenic variation

Preferential expression of proteins by B. burgdorferi in both the tick vector and the mammalian host results in differential expression of antibodies that can be detected by immunoblots. For example, OspA/B is expressed in ticks (Neelakanta et al. 2007), whereas dmpA/B and bmpA/B are expressed in the mammalian host (Pal et al. 2008; Shi et al. 2008). The serological response in early LB would be expected to include proteins that may be downgraded in later disease while the antibody response to later disease would be expected to show different proteins. As with vlsE, antigenic variation within a single immunogenic protein allows B. burgdorferi to evade the host response and so immunblots would be expected to allow only variable detection of some proteins. Fortunately, multiple immunogenic proteins have been described and in recent work a genome-wide proteome array and protein microassay have been used to expand the number of diagnostic antigenic proteins that are useful in serological diagnosis (Barbour et al. 2008; Xu et al. 2008b).

PCR assays

North American practitioners have been reluctant to accept PCR tests as the primary basis for a diagnosis of LB (e.g., Halperin and Wormser 2001). Such tests can show a large variation in specificity among studies, tissue categories, and geographic regions. Meta-analysis of PCR assays carried out in North America and Europe generally show moderate median sensitivity for skin biopsy (69%) and synovial fluid (78%) but low median sensitivity for cerebrospinal fluid (38%) and blood/ plasma/serum (14%) (Aguero-Rosenfeld et al. 2005). The ranges of these values were at least 50% among individual studies, and when the studies were grouped by continent the difference in median sensitivity between North America and Europe ranged from 8% (blood/ plasma/serum) to 50% (cerebrospinal fluid). However, specificity rates for these categories are much higher, usually 100%), with the lowest being 93% (Aguero-Rosenfeld et al. 2005), which means that there are very few false positives. Thus, in spite of extensive documented variation in specificity and high rates of false negatives, PCR tests can be useful for confirming clinical diagnoses in individual cases. For example, a case of seronegative Lyme arthritis has been described where PCR-positive synovial fluid allowed a diagnosis to be made in the absence of a serological response (Holl-Wieden et al. 2007).

Although PCR-based diagnosis of LB in humans is problematic, presumably because spirochetes can be sequestered in tissues that were not tested, this is not such an impediment to the detection of Borrelia in ticks. Numerous studies have consistently demonstrated that whole or partial ticks can be homogenized to give sufficient DNA for identifying a substantial variety of bacterial symbionts (e.g., van Overbeek et al. 2008). Furthermore, DNA-based identification of the ticks themselves is feasible via DNA barcoding or other DNA-based techniques (Sperling and Roe 2009), which should be especially useful for identifying immature stages, where diagnostic characters visible in their morphology are limited.

Future directions

Human cases of LB in Canada can be devastating to affected individuals, not only because of increasingly debilitating health effects over time, but because of the psychologically draining process of obtaining a formal diagnosis that allows treatment via the Canadian health system. It is easy to understand why a diagnosis of LB can be difficult to obtain in the face of its ecological complexity, genetic diversity, and immunological heterogeneity. With so much specialized information to assimilate and comprehend, it can be equally difficult to know where efforts to improve the situation can make a significant difference. Fortunately, it is likely that entomologists can contribute in a number of ways to a positive resolution of the challenges presented by LB.

First, there is a strong need for better means of identifying tick species and for detailed documentation of their distributions across Canada. Morphology-based keys that require only the use of a good microscope have been available for many decades, but relatively little new work on publicly accessible identification guides for ticks in Canada has been done since Gregson (1956). However, a handbook to the ticks of Canada is nearing completion (T. Galloway, University of Manitoba, Winnipeg, personal communication) and should fill an urgent need. Furthermore, there is good potential for DNA-based identification and delimitation of tick species (Sperling and Roe 2009), and internet-accessible guides can supplement these efforts. Such efforts should facilitate localized surveys of tick distributions, which are essential to more effective modeling and prediction of changes in tick and LB distributions in the context of climate change (Ogden et al. 2008a, 2008c, 2008d). The patchy distributions of B. burgdorferi-infected hosts and ticks means that using average numbers of infected ticks across a large area may underestimate the prevalence of LB. Efforts to identify patches should focus on areas where exposure of humans or their companion animals has been reported, because large-scale inventories of ticks are unlikely to pick up infrequent patches. The dispersal and population structure of ticks can be studied using molecular markers such as microsatellites, and the field is ripe for further work of this kind (e.g., Kain et al. 1999).

The second way in which entomologists can contribute, in conjunction with microbiologists, is through more effective identification of Borrelia species and other symbionts in ticks. This will allow more effective study of the factors that regulate the behavior and interaction of ticks with their vertebrate hosts and bacterial symbionts. PCR-based diagnostics of Borrelia species and surveys of the diversity of bacterial strains in ticks are now commonplace. These should enable more comprehensive documentation of the distribution and evolution of these symbionts in spite of the challenges of growing them in culture (Aguero-Rosenfeld et al. 2005). Furthermore, new techniques for in vivo visualization of Borrelia are providing insights into the behavior of spirochetes (Moriarty et al. 2008). Round bodies of B. burgdorferi have also been visualized post mortem in confirmed cases of LB (Miklossy et al. 2008); this method may therefore assist in confirming previously inconclusive cases.

Consistent identification of Borrelia cannot help but increase our understanding of the transmission dynamics of these bacteria in specific ecological or behavioral circumstances. For example, Faulde and Robbins (2008) recently demonstrated that fewer infected ticks were picked up by dragging for the main European vector of LB, I. ricinus, than by collecting from exposed human volunteers, which suggests that Borrelia burgdorferi s.l. may increase the host-finding efficacy of female I. ricinus under natural conditions. Such an effect may explain why some of the low numbers of ticks collected in Canada by dragging or flagging test positive. It also supports the use of passive surveillance, because a higher percentage of positive ticks would be expected from ticks collected on hosts. Furthermore, Borrelia incidence and vector competence should be addressed more comprehensively in tick species other than those of Ixodes. An example is the competence of deer and other ungulates as reservoirs for B. burgdorferi. Even for Ixodes ticks, little is published that gives deer infection rates in Canada beyond the studies done in Ontario by Gallivan et al. (1998). Although the finding obviously needs to be confirmed, the Tennes-see study by Shariat et al. (2007) opens up the possibility that deer are effective reservoir species in some areas, and Dermacentor ticks may even be involved as vectors.

A third major research gap in Canada is the synergistic effect of co-infections in vectors or alternative reservoirs, which opens up opportunities for entomological collaboration with public health researchers as well as with microbiologists. The diversity of species and strains of Borrelia is still incompletely understood and the most important combinations involved in these co-infections are largely unknown. Simultaneous infection by B. burgdorferi and Babesia microti Franca increases the severity of arthritis in mice (Moro et al. 2002). Human infection with both B. burgdorferi and Babesia microti was described in Ontario in 1997, with the recognition that more serious disease symptoms are associated with co-infection (dosSantos and Kain 1998). More severe symptoms continue to be reported for LB cases with co-infections (Rawling et al. 2009). For vectors, Zhong et al. (2007) have demonstrated that in Amblyomma C.L. Koch ticks treated with antibiotics, reproductive fitness is reduced. In their study system, Coxiella sp. Philip was the identified endosymbiont. Because I. scapularis also has an endosymbiont, a Rickettsia-like bacterium (Noda et al. 1997), this information may have relevance to the LB system. Not only would treating the ticks with antibiotics potentially reduce the incidence of B. burgdorferi, it might also reduce the population of the tick vector. The effectiveness of antibiotic-baited traps that target mice (Dolan et al. 2008) may have further advantages for integrated pest management strategies for controlling LB by lowering populations of Ixodes in subsequent years.

Practitioners of integrated pest management and other aspects of economic entomology will recognize a fourth research need: a long-term and broad-scale analysis of the costs and challenges of LB to humans, which is essential to a more effective deployment of resources to combat this disease. Recognizing that human cases are possible across the geographic expanse of Canada is vital to reducing the burden on the public health care system. Furthermore, recognizing and monitoring the changing effects of LB over time will pay dividends on a human scale. In Scotland the cost of treating a case of early LB is estimated to be one-third that of treating late LB (Joss et al. 2003), and early and effective treatment is viewed as a cost-saving measure. In Scotland, regular audits of the interpretation of Western blots that are tailored to local areas has been emphasized. This has resulted in improved management of patients, and it is now recognized that the 58-kilodalton protein is a highly specific indicator of infection by B. burgdorferi (Evans et al. 2005). A revised antigen for IgG Western blotting has been produced and has increased sensitivity for Scottish patients (Mavin et al. 2009). Canadians might do well to follow this example and conduct an audit of the proteins used to establish a positive Western blot. The various ELISA tests are also in need of renewed scrutiny.

Variability and recurrence of symptoms are hallmarks of LB (Cameron et al. 2004; Holl-Wieden et al. 2007; Nardelli et al. 2008). Establishment of the initial infection, its dissemination, and the development of pathology are all stages in this complex disease. Debate is ongoing concerning the severity of symptoms and the role of persistent infection and immunological dysfunction in continued symptoms. The ecology of LB is challenging: at every spatial scale studied so far, the risk is unevenly distributed (Killilea et al. 2008). A coordinated, multidisciplinary, and flexible approach to understanding LB is needed to reduce the burden of this disease in Canada and abroad. Entomologists are in an ideal position to achieve rapprochement between the highly divergent groups of people concerned with LB and to contribute to a better understanding of its practical and intellectual challenges.


We thank Reuben Kaufman, Kathy Magor, Judith Miklossy, George Chaconas, and two anonymous reviewers for comments on an earlier draft of the manuscript, as well as Harvey Artsob, Saswati Das, Terry Galloway, Robbin Lindsay, and Louise Trudel for providing useful information. F.A.H.S. gratefully acknowledges support from a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada and funding from Genome Alberta / Genome British Columbia.



M.E. Aguero-Rosenfeld , G. Wang , I. Schwartz , and G.P. Wormser 2005. Diagnosis of lyme borreliosis. Clinical Microbiology Reviews, 18(3): 484–509. PMID:16020686 doi: 10.1128/CMR.18.3.484-509.2005Google Scholar


A.N. Alekseev , E.A. Arumova , and I.S. Vasilieva 1995. Borrelia burgdorferi sensu lato in female cement plug of Ixodes persulcatus ticks (Acari, Ixodidae). Experimental and Applied Acarology, 19(9): 519–522. PMID:8575271 doi: 10.1007/BF00052920Google Scholar


B.F. Allan , F. Keesing , and R. Ostfeld 2003. Effect of forest fragmentation on Lyme disease risk. Conservation Biology, 17(1): 267–272. doi: 10.1046/j.l523-1739.2003.01260.xGoogle Scholar


J.M. Anderson , and J.G. Valenzuela 2007. Spitacular entry: Borrelia gets help from a tick salivary protein to move from the mammalian host to the arthropod vector. Cell Host and Microbe, 2(1): 3–4. PMID:18005711 doi: 10.1016/j.chom.2007.06.007Google Scholar


R.R. Anderson , and L.C. Harrington 2009. Tick biology for the home owner [on-line]. Available from [accessed 31 May 2009]. Google Scholar


R.R. Arnold , J.E. Russell , W.J. Champion , M. Brewer , and J.J. Gauthier 1982. Bactericidal activity of human lactoferrin: differentiation from the stasis of iron deprivation. Infection and Immunity, 35(3): 792–799 PMID: 6802759. Google Scholar


H. Artsob , M. Garvie , R.J. Cawthorn , B. Horney , R. Maloney , D. Dick , and S. McBurney 1992. Isolation of the Lyme disease spirochete, Borrelia burgdorferi, from Ixodes dammini (Acari: Ixodidae) collected on Prince Edward Island, Canada. Journal of Medical Entomology, 29(6): 1063–1066 PMID: 1460625. Google Scholar


H. Artsob , R. Maloney , G. Conboy , and B. Horney 2000. Identification of Ixodes scapularis in Newfoundland, Canada. Canada Communicable Disease Report, 26(16): 133–134. Google Scholar


C. Ballantyne 2008. The chronic debate over Lyme disease. Nature Medicine, 14(11): 1135–1139. PMID:18989271 doi: 10.1038/nml1108-1135Google Scholar


S. Banerjee 1993. Isolation of Borrelia burgdorferi in British Columbia. Canada Diseases Weekly Report No. 19–24. pp. 204–205. Google Scholar


S.N. Banerjee , M. Banerjee , K. Fernando , M.Y. Dong , J.A. Smith , and D. Cook 1995a. Isolation of Borrelia burgdorferi, the Lyme disease spirochete from rabbit ticks, Haemaphysalis leporispalustris from Alberta. Journal of Spirochetal and Tick-Borne Diseases, 2: 23–24. Google Scholar


S.N. Banerjee , C.I. Christensen , and J.D. Scott 1995b. Lyme disease in Canada. Canada Communicable Disease Report 21(10). PMID: 7881380. Google Scholar


T. Bankhead , and G. Chaconas 2007. The role of VlsE antigenic variation in the Lyme disease spirochete: persistence through a mechanism that differs from other pathogens. Molecular Microbiology, 65(6): 1547–1558. PMID: 1771 4442 doi:  10.1111/j.1365-2958.2007.05895.xGoogle Scholar


A.G. Barbour , and S.F. Hayes 1986. Biology of Borrelia species. Microbiological Reviews, 50(4): 381–400 PMID:3540570. Google Scholar


A.G. Barbour , A. Jasinskas , M.A. Kayala , D.H. Davies , A.C. Steere , P. Baldi , and P.L. Feigner 2008. A genome-wide proteome array reveals a limited set of immunogens in natural infections of humans and white-footed mice with Borrelia burgdorferi. Infection and Immunity, 76(8): 3374–3389. PMID: 18474646 doi: 10.1128/IAI.00048-08Google Scholar


I.K. Barker , and L.R. Lindsay 2000. Lyme borreliosis in Ontario: determining the risks. Canadian Medical Association Journal, 162(11): 1573–1574 PMID: 10862232. Google Scholar


I.K. Barker , G.A. Surgeoner , S.A. McEwen , and H. Artsob 1988. Borrelia burgdorferi, the agent of Lyme disease, in tick vectors and wildlife reservoirs in southern Ontario. Ontario Disease Surveillance Report No. 9. pp. 151–154. Google Scholar


I.K. Barker , L.R. Lindsay , G.D. Campbell , G.A. Surgeoner , and S.A. McEwen 1993. The groundhog tick Ixodes cookei (Acari: Ixodidae): a poor potential vector of Lyme borreliosis. Journal of Wildlife Diseases, 29: 416–422. Google Scholar


S. Barthold 2000. Lyme borreliosis. In Persistent bacterial infections. Edited by J.P. Nataro , M.J. Blaser , and S. Cunningham-Rundles . ASM Press, Washington, D.C. pp. 281–304. Google Scholar


J. Bjerkelund 1997. New Brunswick Veterinary Medical Association Newsletter June 1997, Saint John, New Brunswick, pp. 15–16. Google Scholar


O.J. Bjerrum , and N.H.H. Heegaard 2001. Western blotting. In Encyclopedia of life sciences. John Wiley and Sons, London, pp. 1–6. Google Scholar


E. Bollegraaf 1988. Lyme disease in Canada. Canada Diseases Weekly Report No. 14–22. pp. 95–97. Google Scholar


R.L. Bratton , J.W. Whiteside , M.J. Hovan , R.L. Engle , and F.D. Edwards 2008. Diagnosis and treatment of Lyme disease. Mayo Clinic Proceedings, 83(5): 566–571. PMID: 18452688 doi:  10.4065/83.5.566Google Scholar


F. Breier , G. Khanakah , G. Stanek , G. Kunz , E. Aberer , B. Schmidt , and G. Tappeiner 2001. Isolation and polymerase chain reaction typing of Borrelia afzelii from a skin lesion in a seronegative patient with generalized ulcerating bullous lichen sclerosus et atrophicus. The British Journal of Dermatology, 144(2): 387– 392. PMID:11251580 doi: 10.1046/j.1365-2133. 2001.04034.xGoogle Scholar


D. Brisson , D.E. Dykhuizen , and R.S. Ostfeld 2008. Conspicuous impacts of inconspicuous hosts on the Lyme disease epidemic. Proceedings of the Royal Society, Biological Sciences, 275: 227–235. Google Scholar


British Columbia Ministry of Health. 2008. Press release: Lyme disease in B.C., February 29 2008 [on-line]. Available from [accessed 21 February 2009]. Google Scholar


Ø. Brorson , S.H. Brorson 1998. In vitro conversion of Borrelia burgdorferi to cystic forms in spinal fluid, and transformation to mobile spirochetes by incubation in BSK-H medium. Infection, 26(3): 144–150. PMID:9646104 doi: 10.1007/BF02771839Google Scholar


Ø. Brorson , S.H. Brorson 2004. An in vitro study of the susceptibility of mobile and cystic forms of Borrelia burgdorferi to tinidazole. International Microbiology, 7(2): 139–142 PMID:15248163. Google Scholar


P. Brouqui , F. Bacellar , G. Baranton , R.J. Birtles , A. Bjoërsdorff , J.R. Blanco , et al. 2004. Guidelines for the diagnosis of tick-borne bacterial diseases in Europe. Clinical Microbiology and Infection, 10(12): 1108–1132. PMID: 15606643 doi: 10.1111/j.l469-0691.2004.01019.xGoogle Scholar


J. Bunikis , U. Garpmo , J. Tsao , J. Berglund , D. Fish , and A.G. Barbour 2004. Sequence typing reveals extensive strain diversity of the Lyme borreliosis agents Borrelia burgdorferi in North America and Borrelia afzelii in Europe. Microbiology, 150(6): 1741–1755. PMID:1518 4561 doi: 10.1099/mic.0.26944-0Google Scholar


W. Burgdorfer , A.G. Barbour , S.F. Hayes , J.L. Benach , E. Grunwaldt , and J.P. Davis 1982. Lyme disease — a tick-borne spirochetosis? Science (Washington, D.C.), 216(4552): 1317–1319. PMID:7043737 doi: 10.1126/science.7043737Google Scholar


E.C. Burgess , and L.A. Patrican 1987. Oral infection of Peromyscus maniculatus with Borrelia burgdorferi and subsequent transmission by Ixodes dammini. The American Journal of Tropical Medicine and Hygiene, 36(2): 402–407 PMID:3826500. Google Scholar


T.R. Burkot , G.O. Maupin , B.S. Schneider , C. Denatale , C.M. Happ , J.S. Rutherford , and N.S. Zeidner 2001. Use of a sentinel host system to study the questing behavior of Ixodes spinipalpis and its role in the transmission of Borrelia bissettii, human granulocytic ehrlichiosis, and Babesia microti. The American Journal of Tropical Medicine and Hygiene, 65(4): 293–299 PMID: 11693872. Google Scholar


F.C. Cabello , H.P. Godfrey , and S.A. Newman 2007. Hidden in plain sight: Borrelia burgdorferi and the extracellular matrix. Trends in Microbiology, 15(8): 350–354. PMID: 17600717 doi:  10.1016/j.tim.2007.06.003Google Scholar


D.J. Cameron 2009. Clinical trials validate the severity of persistent Lyme disease symptoms. Medical Hypotheses, 72(2): 153–156. PMID: 19013025 doi: 10.1016/j.mehy.2008.09.030Google Scholar


D.J. Cameron , A. Gaito , N. Harris , G. Bach , S. Bellovin , K. Bock , et al. 2004. Evidence-based guidelines for the management of Lyme disease. Expert Review of Anti-Infective Therapy, 2(1 Suppl): S1–S13. PMID:15581390 doi: 10.1586/14789072.2.1.S1Google Scholar


Canadian Lyme Disease Foundation. 2009. Ticks of Canada [online]. Available from [accessed 25 March 2009]. Google Scholar


Canadian Paediatric Society (CPS). 2009. Lyme disease in Canada: Q and A for paediatricians. Paediatrics and Child Health (Oxford), 14: 103–105. Google Scholar


Canadian Public Health Laboratory Network (CPHLN). 2007. The laboratory diagnosis of Lyme borreliosis: guidelines from the Canadian Public Health Laboratory Network. The Canadian Journal of Infectious Diseases and Medical Microbiology. 18(2): 145–148 PMID: 18923770. Google Scholar


S. Casjens , N. Palmer , R. van Vugt , W.M. Huang , B. Stevenson , P. Rosa , et al. 2000. A bacterial genome in flux: the twelve linear and nine circular extrachromosomal DNAs in an infectious isolate of the Lyme disease spirochete Borrelia burgdorferi. Molecular Microbiology, 35(3): 490–516. PMID:10672174 doi: 10.1046/J.1365-2958.2000.01698.xGoogle Scholar


Centers for Disease Control and Prevention (CDC). 1995. Recommendations for test performance and interpretation. In Proceedings of the Second National Conference on Serologic Diagnosis of Lyme Disease. Morbidity and Mortality Weekly Report, 44: 590–591. Google Scholar


Centers for Disease Control and Prevention (CDC). 2007. Lyme disease — United States, 2003–2005. Morbidity and Mortality Weekly Report, 56(23): 573–576 PMID: 17568368. Google Scholar


G. Chaconas 2005. Hairpin telomeres and genome plasticity in Borrelia: all mixed up in the end. Molecular Microbiology, 58(3): 625–635. PMID: 16238614 doi:  10.1111/j.1365-2958.2005.04872.xGoogle Scholar


D. Charron , and P. Sockett 2005. Signs of change, signs of trouble: finding the evidence in climate change: preparing for the health impacts. Health Policy Research Bulletin, 11: 27–30. Google Scholar


K. Clark , A. Hendricks , and D. Burge 2005. Molecular identification and analysis of Borrelia burgdorferi sensu lato in lizards in the southeastern United States. Applied and Environmental Microbiology, 71(5): 2616–2625. PMID: 1587 0353 doi: 10.1128/AEM.71.5.2616-2625.2005Google Scholar


J.R. Clover , and R.S. Lane 1995. Evidence implicating nymphal Ixodes pacificus (Acari: Ixodidae) in the epidemiology of Lyme disease in California. The American Journal of Tropical Medicine and Hygiene, 53(3): 237–240 PMID:7573703. Google Scholar


Connecticut General Assembly. 2009. An act concerning the use of long-term antibiotics for the treatment of Lyme disease [online]. Available from [accessed 30 May 2009]. Google Scholar


A. Costero 1990. Identification of the Lyme disease vector in Canada. Canada Diseases Weekly Report No. 16–30. pp. 142–147. Google Scholar


K.A. Craig-Mylius , M. Lee , K.L. Jones , and L.J. Glickstein 2009. Arthritogenicity of Borrelia burgdorferi and Borrelia garinii: comparison of infection in mice. The American Journal of Tropical Medicine and Hygiene, 80(2): 252–258 PMID: 19190223. Google Scholar


M. Crippa , O. Rais , and L. Gern 2002. Investigations on the mode and dynamics of transmission and infectivity of Borrelia burgdorferi sensu stricto and Borrelia afzelii in Ixodes ricinus ticks. Vector Borne and Zoonotic Diseases (Larchmont, N.Y.), 2(1): 3–9. PMID: 12656125 doi:  10.1089/153036602760260724Google Scholar


S.J. Cutler , J. Moss , M. Fukunaga , D.J.M. Wright , D. Fekade , and D. Warrell 1997. Borrelia recurrentis characterization and comparison with relapsing-fever, Lyme-associated, and other Borrelia spp. International Journal of Systematic Bacteriology, 47(4): 958–968 PMID:9336893. Google Scholar


J.M. Doby , J.F. Anderson , A. Couatarmanac'h , L.A. Magnarelli , and A. Martin 1987. Lyme disease in Canada with possible transmission by an insect. Zentralblatt für Bakteriologie, Mikrobiologie und Hygiene Series A, 263: 488–490. Google Scholar


M.C. Dolan , N.S. Zeidner , E. Gabitzsch , G. Dietrich , J.N. Borchert , R.M. Poché , and J. Piesman 2008. A doxycycline hyclate rodent bait formulation for prophylaxis and treatment of tick-transmitted Borrelia burgdorferi. The American Journal of Tropical Medicine and Hygiene, 78(5): 803–805 PMID: 18458316. Google Scholar


S.T. Donta 2002. Late and chronic Lyme disease. The Medical Clinics of North America, 86(2): 341–349., vii PMID: 11982305 doi:  10.1016/S0025-7125(03)00090-7Google Scholar


S.T. Donta 2003. Macrolide therapy of chronic Lyme disease. Medical Science Monitor, 9: 136–142. Google Scholar


S.T. Donta 2007. Lyme disease guidelines — it's time to move forward. Clinical Infectious Diseases, 44(8): 1134–1135, author reply 1137–1139. PMID:17366465 doi: 10.1086/51297Google Scholar


C. dosSantos , and K. Kain 1998. Concurrent babesiosis and Lyme disease diagnosed in Ontario. Canada Communicable Disease Report No. 24–12. pp. 1–3. Google Scholar


F. Dressier , J.A. Whalen , B.N. Reinhardt , and A.C. Steere 1993. Western blotting in the serodiagnosis of Lyme disease. The Journal of Infectious Diseases, 167(2): 392–400 PMID:8380611. Google Scholar


L.A. Durden , and J.E. Keirans 1996. Nymphs of the genus Ixodes (Acari Ixodidae) of the United States:taxonomy, identification key, distribution, hosts, and medical/veterinary importance. Entomological Society of America, Lanham, Maryland, pp. 1–95. Google Scholar


F. Egberts , M. Moller , E. Proksch , and T. Schwarz 2008. Multiple erythema migrans — manifestation of systemic cutaneous borreliosis. Journal of the German Society of Dermatology, 6: 350–353. Google Scholar


L. Eisen , and R.S. Lane 2002. Vectors of Borrelia burgdorferi sensu lato. In Lyme borreliosis: biology, epidemiology and control. Edited by J. Gray , O. Kahl , R.S. Lane , and G. Stanek . CABI Publishing, New York. Google Scholar


R. Evans , S. Mavin , and D.O. Ho-Yen 2005. Audit of the laboratory diagnosis of Lyme disease in Scotland. Journal of Medical Microbiology, 54(12): 1139–1141. PMID:16278426 doi: 10.1099/jmm.0.46003-0Google Scholar


M. Exner 2004. Borrelia spp. In Encyclopedia of medical genomics and proteomics. Volume 1. Part 1. pp. 146–149. Google Scholar


R.C. Falco , and D. Fish 1991. Horizontal movement of adult Ixodes dammini (Acari: Ixodidae) attracted to CO2-baited traps. Journal of Medical Entomology, 28(5): 726–729 PMID: 1941943. Google Scholar


B.A. Fallon , J.G. Keilp , K.M. Corbera , E. Petkova , C.B. Britton , E. Dwyer , et al. 2008. A randomized, placebo-controlled trial of repeated IV antibiotic therapy for Lyme encephalopathy. Neurology, 70(13): 992–1003. PMID: 17928580 doi: 10.1212/01.WNL.0000284604.611 60.2dGoogle Scholar


M.K. Faulde , and R.G. Robbins 2008. Tick infestation risk and Borrelia burgdorferi s.l. infection-induced increase in host-finding efficacy of female Ixodes ricinus under natural conditions. Experimental and Applied Acarology, 44: 127–145. Google Scholar


K. Fernando , M.-K. Lee , Q. Wong , K. Burgess , L. Durden , and M. Morshed 2008. First Isolation of Borrelia burgdorferi from Ixodes cookei removed from a dog in Alberta. The Canadian Journal of Infectious Diseases and Medical Microbiology, 19: 130. Google Scholar


E. Fikrig , S.W. Barthold , N. Marcantonio , K. Deponte , F.S. Kantor , and R.A. Flavell 1992. Roles of OspA, OspB, and flagellin in protective immunity to Lyme borreliosis in laboratory mice. Infection and Immunity, 60(2): 657–661 PMID: 1730500. Google Scholar


V. Fingerle , G. Liegl , U. Munderloh , and B. Wilske 1998. Expression of outer surface proteins A and C of Borrelia burgdorferi in Ixodes ricinus ticks removed from humans. Medical Microbiology and Immunology, 187(2): 121–126. PMID:9832327 doi: 10.1007/s004300050083Google Scholar


K.R. Forward 2005. Lyme Disease: dispelling the myth. The Canadian Journal of Continuing Medical Education, 17: 73–75. Google Scholar


C.L. Fritz 2009. Emerging tick-borne diseases. The Veterinary Clinics of North America, Small Animal Practice, 39(2): 265–278. PMID: 19185193 doi: 10.1016/j.cvsm.2008.10.019Google Scholar


D.P. Furman , and E.C. Loomis 1984. the ticks of California. Bulletin of the California Insect Survey, 25. Google Scholar


G.J. Gallivan , I.K. Barker , H. Artsob , L.A. Magnarelli , J.T. Robinson , and D.R. Voigt 1998. Serologic survey for antibodies to Borrelia burgdorferi in white-tailed deer in Ontario. Journal of Wildlife Diseases, 34(2): 411–414 PMID:9577798. Google Scholar


T.D. Galloway 2002. Getting to know your ticks. Blue Jay, 60: 107–112. Google Scholar


M. Gammons , and G. Salam 2002. Tick removal. American Family Physician, 66(4): 643–645 PMID: 12201558. Google Scholar


A.G. Gatewood , K.A. Liebman , G. Vourc'h , J. Bunikis , S.A. Hamer , R. Cortinas , et al. 2009. Climate and tick seasonality are predictors of Borrelia burgdorferi genotype distribution. Applied and Environmental Microbiology, 75(8): 2476–2483. PMID:19251900 doi: 10.1128/AEM.02633-08Google Scholar


S.T. Giery , and R.S. Ostfeld 2007. The role of lizards in the ecology of Lyme disease in two endemic zones of the northeastern United States. The Journal of Parasitology, 93(3): 511–517. PMID:17626342 doi: 10.1645/GE-1053R1.1Google Scholar


M.A. Gilbert , E.A. Morton , S.F. Bundle , and D.S. Samuels 2007. Artificial regulation of ospC expression in Borrelia burgdorferi. Molecular Microbiology, 63(4): 1259–1273. PMID: 17257307 doi: 10.1111/j.l365-2958.2007.05593.xGoogle Scholar


H.S. Ginsberg , P.A. Buckley , M.G. Balmforth , E. Zhioua , S. Mitra , and F.G. Buckley 2005. Reservoir competence of native North American birds for the Lyme disease spirochete, Borrelia burgdorfieri. Journal of Medical Entomology, 42(3): 445–449. PMID:15962798 doi: 10.1603/0022-2585(2005)042[0445:RCONNA]2.0.CO;2Google Scholar


H.J. Girschick , H.I. Huppertz , H. Rüssmann , V. Krenn , and H. Karch 1996. Intracellular persistence of Borrelia burgdorferi in human synovial cells. Rheumatology International, 16(3): 125–132 PMID:8893378 doi: 10.1007/BF01409 985Google Scholar


J.S. Gray 1985. A carbon dioxide trap for prolonged sampling of Ixodes ricinus L. populations. Experimental and Applied Acarology, 1(1): 35–44. PMID:3939717 doi: 10.1007/BF012 62198Google Scholar


J.S. Gray , O. Kahl , R.S. Lane , and G. Stanek (Editors). 2002. Lyme borreliosis: biology, epidemiology and control. CABI Publishing, New York. Google Scholar


J.D. Gregson 1956. The Ixodidae of Canada. Publication 930, Canada Department of Agriculture, Ottawa, Ontario. Google Scholar


J.J. Halperin , and G.P. Wormser 2001. Of fleas and ticks on cats and mice.... Archives of Neurology, 58(9): 1345–1347. PMID: 11559304 doi:  10.1001/archneur.58.9.1345Google Scholar


K. Hanincová , N.H. Ogden , M. Diuk-Wasser , C.J. Pappas , R. Iyer , D. Fish , I. Schwartz , and K. Kurtenbach 2008. Fitness variation of Borrelia burgdorferi sensu stricto strains in mice. Applied and Environmental Microbiology, 74(1): 153–157. PMID:17981941 doi: 10.1128/AEM.01567-07Google Scholar


A.L. Hassett , D.C. Radvanski , S. Buyske , S.V. Savage , M. Gara , J.I. Escobar , and L.H. Sigal 2008. Role of psychiatric comorbidity in chronic Lyme disease. Arthritis and Rheumatism, 59(12): 1742–1749. PMID: 19035409 doi: 10.1002/art.24314Google Scholar


P. Hildenbrand , D.E. Craven , R. Jones , and P. Nemeskal 2009. Lyme neuroborreliosis: manifestations of a rapidly emerging zoonosis. American Journal of Neuroradiology, 30(6): 1079–1087. PMID:19346313 doi:  10.3174/ajnr. A1579Google Scholar


E. Hodzic , S. Feng , K. Holden , K.J. Freet , and S.W. Barthold 2008. Persistence of Borrelia burgdorferi following antibiotic treatment in mice. Antimicrobial Agents and Chemotherapy, 52(5): 1728–1736. PMID:18316520 doi: 10.1128/AAC.01050-07Google Scholar


A. Hojgaard , R.J. Eisen , and J. Piesman 2008. Transmission dynamics of Borrelia burgdorferi s.s. during the key third day of feeding by nymphal Ixodes scapularis (Acari: Ixodidae). Journal of Medical Entomology, 45(4): 732– 736. PMID:18714875 doi:  10.1603/0022-2585(2008)45[732:TDOBBS]2.0.CO;2Google Scholar


A. Holl-Wieden , S. Suerbaum , and H.J. Girschick 2007. Seronegative Lyme arthritis. Rheumatology International, 27(11): 1091–1093. doi:  10.1007/s00296-007-0333-6Google Scholar


V. Horobik , F. Keesing , and R.S. Ostfeld 2006. Abundance and Borrelia burgdorferi-infection prevalence of nymphal Ixodes scapularis ticks along forest-field edges. EcoHealth, 3(4): 262– 268. doi:  10.1007/s10393-006-0065-1Google Scholar


L. Houhamdi , and D. Raoult 2005. Excretion of living Borrelia recurrentis in feces of infected human body lice. The Journal of Infectious Diseases, 191(11): 1898–1906. PMID:15871124 doi:  10.1086/429920Google Scholar


K.P. Hunfeld , E. Ruzic-Sabljic , D.E. Norris , P. Kraiczy , and F. Strle 2005. In vitro susceptibility testing of Borrelia burgdorferi sensu lato isolates cultured from patients with erythema migrans before and after antimicrobial chemotherapy. Antimicrobial Agents and Chemotherapy, 49(4): 1294–1301. PMID: 1579 3100 doi: 10.1128/AAC49.4.1294-1301.2005Google Scholar


IDEXX Laboratories, Inc. 2008. Incidence of heartworm, Ehrlichia canis, Lyme disease, and anplasmosis in dogs across Canada as determined by the IDEXX SNAP® 3Dx® and 4Dx® tests. 2007 national incidence study results. IDEXX Laboratories, Inc., Markham, Ontario, pp. 1–13. Google Scholar


R.C. Johnson , G.P. Schmid , F.W. Hyde , A.G. Steigerwalt , and D.J. Brenner 1984. Borrelia burgdorferi sp. nov.: etiologic agent of Lyme disease. International Journal of Systematic Bacteriology, 34: 496–497. Google Scholar


A.W.L. Joss , M.M. Davidson , D.O. Ho-Yen , and A. Ludbrook 2003. Lyme disease — what is the cost for Scotland? Public Health, 117(4): 264–273 PMID: 12966749 doi:  10.1016/S0033-3506(03)00067-2Google Scholar


V.Lj. Jovicić , E.M. Grego , B.L. Lako , B.M. Ristović , Z.A. Lepsanović , and N.T. Stajkovic 2003. Improved serodiagnosis of early Lyme borreliosis: immunoblot with local Borrelia afzelii strain. Acta Pathologica, Microbiologica et Immunologica, 111(11): 1053–1059. PMID: 14629271 doi:  10.1111/j.1600-0463.2003.apm111 1107.xGoogle Scholar


O. Kahl , C. Janetzki-Mittmann , J.S. Gray , R. Jonas , J. Stein , and R. de Boer 1998. Risk of infection with Borrelia burgdorferi sensu lato for a host in relation to the duration of nymphal Ixodes ricinus feeding and the method of tick removal. Zentralblatt für Bakteriologie, 287(1–2): 41–52 PMID:9532263. Google Scholar


O. Kahl , L. Gern , L. Eisen , and R.S. Lane 2002. Ecological research on Borrelia burgdorferi sensu lato: terminology and some methodological pitfalls. In Lyme borreliosis: biology, epidemiology and control. Edited by J. Gray , O. Kahl , R.S. Lane , and G. Stanek . CABI Publishing, New York. Google Scholar


D.E. Kain , F.A.H. Sperling , and R.S. Lane 1997. Population genetic structure of Ixodes pacificus (Acari: Ixodidae) using allozymes. Journal of Medical Entomology, 34(4): 441–450 PMID: 9220679. Google Scholar


D.E. Kain , F.A.H. Sperling , H.V. Daly , and R.S. Lane 1999. Mitochondrial DNA sequence variation in Ixodes pacificus (Acari: Ixodidae). Heredity, 83(4): 378–386. PMID: 10583539 doi:  10.1038/sj.hdy.6886110Google Scholar


R. Kaiser 2000. False-negative serology in patients with neuroborreliosis and the value of employing of different borrelial strains in serological assays. Journal of Medical Microbiology, 49(10): 911– 915 PMID:11023188. Google Scholar


J.E. Keirans , and C.M. Clifford 1978. The genus Ixodes in the United States: a scanning electron microscope study and key to the adults. Journal of Medical Entomology. Supplement 2. Google Scholar


M.E. Killilea , A. Swei , R.S. Lane , C.J. Briggs , and R.S. Ostfeld 2008. Spatial dynamics of Lyme disease: a review. EcoHealth, 5(2): 167– 195. PMID: 18787920 doi:  10.1007/s10393-008-0171-3Google Scholar


D.I. Kosik-Bogacka , W. Kuźna-Grygiel , and M. Jaborowska 2007. Ticks and mosquitoes as vectors of Borrelia burgdorferi s. 1. in the forested areas of Szczecin. Folia Biologica, 55(3–4): 143–146. PMID:18274258 doi: 10.3409/173491607781 492542Google Scholar


M. Kudryashev , M. Cyrklaff , W. Baumeister , M.M. Simon , R. Wallich , and F. Frischknecht 2009. Comparative cryo-electron tomography of pathogenic Lyme disease spirochetes. Molecular Microbiology, 71(6): 1415–1434. PMID:1921 0619 doi: 10.1111/j.1365-2958.2009.06613.xGoogle Scholar


K. Kurtenbach , A. Dizij , H.M. Seitz , G. Margos , S.E. Moter , M.D. Kramer , et al . 1994. Differential immune responses to Borrelia burgdorferi in European wild rodent species influence spirochete transmission to Ixodes ricinus L. (Acari: Ixodidae). Infection and Immunity, 62(12): 5344–5352 PMID:7960113. Google Scholar


K. Kurtenbach , H. Kampen , A. Dizij , S. Arndt , H.M. Seitz , U.E. Schaible , and M.M. Simon 1995. Infestation of rodents with larval Ixodes ricinus (Acari: Ixodidae) is an important factor in the transmission cycle of Borrelia burgdorferi s.l. in German woodlands. Journal of Medical Entomology, 32(6): 807–817 PMID: 8551503. Google Scholar


K. Kurtenbach , H.-S. Sewell , N.H. Ogden , S.E. Randolph , and P.A. Nuttall 1998. Serum complement sensitivity as a key factor in Lyme disease ecology. Infection and Immunity, 66(3): 1248–1251 PMID:9488421. Google Scholar


K. Kurtenbach , S. De Michelis , S. Etti , S.M. Schäfer , H.-S. Sewell , V. Brade , and P. Kraiczy 2002a. Host association of Borrelia burgdorferi sensu lato — the key role of host complement. Trends in Microbiology, 10(2): 74–79 PMID: 11827808 doi: 10.1016/S0966-842X(01)02298-3Google Scholar


K. Kurtenbach , S.M. Schäfer , H.-S. Sewell , M. Peacey , A. Hoodless , P.A. Nuttall , and S.E. Randolph 2002b. Differential survival of Lyme borreliosis spirochetes in ticks that feed on birds. Infection and Immunity, 70(10): 5893– 5895. PMID: 12228325 doi: 10.1128/IAI.70.10.5893-5895.2002Google Scholar


K. Kurtenbach , K. Hanincová , J. Tsao , G. Margos , D. Fish , and N.H. Ogden 2006. Fundamental processes in the evolutionary ecology of Lyme borreliosis. Nature Reviews Microbiology, 4(9): 660–669. PMID: 16894341 doi: 10.1038/nrmicro1475Google Scholar


R.S. Lane 1990. Susceptibility of the western fence lizard (Sceloporus occidentalis) to the Lyme borreliosis spirochete (Borrelia burgdorferi). The American Journal of Tropical Medicine and Hygiene, 42(1): 75–82 PMID:2301709. Google Scholar


R.S. Lane , and J.E. Loye 1991. Lyme disease in California: interrelationship of ixodid ticks (Acari), rodents, and Borrelia burgdorferi. Journal of Medical Entomology, 28(5): 719–725 PMID:1941942. Google Scholar


R.S. Lane , D.B. Steinlein , and J. Mun 2004. Human behaviors elevating exposure to Ixodes pacificus (Acari: Ixodidae) nymphs and their associated bacterial zoonotic agents in a hardwood forest. Journal of Medical Entomology, 41(2): 239–248 PMID: 15061284. Google Scholar


M.B. Lawrenz , J.M. Hardham , R.T. Owens , J. Nowakowski , A.C. Steere , G.P. Wormser , and S.J. Norris 1999. Human antibody responses to VlsE antigenic variation protein of Borrelia burgdorferi. Journal of Clinical Microbiology, 37(12): 3997–4004 PMID: 10565921. Google Scholar


A.M. Lebech , K. Hansen , B. Wilske , and M. Theisen 1994. Taxonomic classification of 29 Borrelia burgdorferi strains isolated from patients with Lyme borreliosis: a comparison of five different phenotypic and genotypic typing schemes. Medical Microbiology and Immunology, 183(6): 325–341. PMID:7541107 doi:  10.1007/BF00196683Google Scholar


J.F. Levine , M.L. Wilson , and A. Spielman 1985. Mice as reservoirs of the Lyme disease spirochete. The American Journal of Tropical Medicine and Hygiene, 34(2): 355–360 PMID:3985277. Google Scholar


F.T. Liang , A.C. Steere , A.R. Marques , B.J.B. Johnson , J.N. Miller , and M.T. Philipp 1999. Sensitive and specific serodiagnosis of Lyme disease by enzyme-linked immunosorbent assay with a peptide based on an immunodominant conserved region of Borrelia burgdorferi VlsE. Journal of Clinical Microbiology, 37: 3990–3996 PMID: 10565920. Google Scholar


F.T. Liang , M.B. Jacobs , L.C. Bowers , and M.T. Philipp 2002. An immune evasion mechanism for spirochetal persistence in Lyme borreliosis. The Journal of Experimental Medicine, 195(4): 415–422. PMID: 11854355 doi:  10.1084/jem.20011870Google Scholar


E.E. Lindquist , K.W. Wu , and J.H. Redner 1999. A new species of the tick genus Ixodes (Acari: Ixodidae) parasitic on mustelids (Mammalia: Carnivora in Canada. The Canadian Entomologist, 131: 151–170. Google Scholar


L.R. Lindsay , I.K. Barker , G.A. Surgeoner , S.A. McEwen , L.A. Elliott , and J. Kolar 1991. Apparent incompetence of Dermacentor variabilis (Acari: Ixodidae) and fleas (Insecta: Siphonaptera) as vectors of Borrelia burgdorferi in an Ixodes dammini endemic area of Ontario, Canada. Journal of Medical Entomology, 28(5): 750–753 PMID: 1941949. Google Scholar


L.R. Lindsay , S.W. Mathison , I.K. Barker , S.A. McEwen , T.J. Gillespie , and G.A. Surgeoner 1999a. Microclimate and habitat in relation to Ixodes scapularis (Acari: Ixodidae) populations on Long Point, Ontario, Canada. Journal of Medical Entomology, 36(3): 255–262 PMID: 10337093. Google Scholar


L.R. Lindsay , S.W. Mathison , I.K. Barker , S.A. McEwen , and G.A. Surgeoner 1999b. Abundance of Ixodes scapularis (Acari: Ixodidae) larvae and nymphs in relation to host density and habitat on Long Point, Ontario. Journal of Medical Entomology, 36(3): 243–254 PMID: 10337092. Google Scholar


R. Lindsay , H. Artsob , T. Galloway , and G. Horsman 1999c. Vector of Lyme borreliosis, Ixodes scapularis, identified in Saskatchewan. Canada Communicable Disease Report, 25(9). pp. 81–83 PMID: 10079579. Google Scholar


J.A. Livengood , and R.D. Gilmore Jr. 2006. Invasion of human neuronal and glial cells by an infectious strain of Borrelia burgdorferi. Microbes and Infection, 8(14–15): 2832–2840. PMID: 17045505 doi:  10.1016/j.micinf.2006.08.014Google Scholar


K. LoGiudice , R.S. Ostfeld , K.A. Schmidt , and F. Keesing 2003. The ecology of infectious disease: effects of host diversity and community composition on Lyme disease risk. Proceedings of the National Academy of Sciences of the United States of America, 100(2): 567–571. PMID: 12525705 doi:  10.1073/pnas.0233733100Google Scholar


S.W. Luger 1990. Lyme disease transmitted by a biting fly. The New England Journal of Medicine, 322(24): 1752. PMID:2342543. Google Scholar


Y. Ma , A. Sturrock , and J.J. Weis 1991. Intracellular localization of Borrelia burgdorferi within human endothelial cells. Infection and Immunity, 59(2): 671–678 PMID: 1987083. Google Scholar


S.G. Mackenzie 1990. Lyme disease in Canada. Canada Diseases Weekly Report No. 16–30. pp. 141–142. Google Scholar


L.A. Magnarelli , J.F. Anderson , and A.G. Barbour 1986. The etiologic agent of Lyme disease in deer flies, horse flies, and mosquitoes. The Journal of Infectious Diseases, 154(2): 355–358 PMID:2873190. Google Scholar


G. Margos , A.G. Gatewood , D.M. Aanensen , K. Hanincová , D. Terekhova , S.A. Vollmer , et al. 2008. MLST of housekeeping genes captures geographic population structure and suggests a European origin of Borrelia burgdorferi. Proceedings of the National Academy of Sciences of the United States of America, 105(25): 8730– 8735. PMID:18574151 doi: 10.1073/pnas.0800323 105Google Scholar


L. Margulis , A. Maniotis , J. MacAllister , J. Scythes , O. Brorson , J. Hall , W.E. Krumbein , and M.J. Chapman 2009. Spirochete round bodies. Syphilis, Lyme disease and AIDS: resurgence of “the great imitator”? Symbiosis, 47: 51–58. Google Scholar


T.N. Mather , M.C. Nicholson , E.F. Donnelly , and B.T. Matyas 1996. Entomologic index for human risk of Lyme disease. American Journal of Epidemiology, 144(11): 1066–1069 PMID: 8942438. Google Scholar


S. Mavin , R. Evans , R.M. Milner , J.M.W. Chatterton , and D.O. Ho-Yen 2009. Local Borrelia burgdorferi sensu stricto and Borrelia afzelii strains in a single mixed antigen improves western blot sensitivity. Journal of Clinical Pathology, 62(6): 552–554. PMID: 19240047 doi:  10.1136/jcp.2008.063461Google Scholar


J. Miklossy 2008. Biology and neuropathology of dementia in syphilis and Lyme disease. In Handbook of clinical neurology; dementias. Volume 89. Edited by C. Duyckaerts and I. Litvan . Elsevier, Amsterdam; New York. Google Scholar


J. Miklossy , K. Khalili , L. Gern , R.L. Ericson , P. Darekar , L. Bolle , J. Hurlimann , and B.J. Paster 2004. Borrelia burgdorferi persists in the brain in chronic Lyme neuroborreliosis and may be associated with Alzheimer disease. Journal of Alzheimer's Disease, 6: 639–649. Google Scholar


J. Miklossy , A. Kis , A. Radenovic , L. Miller , L. Forro , R. Martins , et al. 2006. Beta-amyloid deposition and Alzheimer's type changes induced by Borrelia spirochetes. Neurobiology of Aging, 27(2): 228–236. PMID:15894409 doi: 10.1016/j.neurobiolaging.2005.01.018Google Scholar


J. Miklossy , S. Kasas , A.D. Zurn , S. McCall , S. Yu , and P.L. McGeer 2008. Persisting atypical and cystic forms of Borrelia burgdorferi and local inflammation in Lyme neuroborreliosis. Journal of Neuroinflammation, 5(1): 40. doi: 10.1186/1742-2094-5-40 PMID:18817547Google Scholar


T.J. Moriarty , M.U. Norman , P. Colarusso , T. Bankhead , P. Kubes , G. Chaconas , and J. Coburn 2008. Real-time high resolution 3D imaging of the Lyme disease spirochete adhering to and escaping from the vasculature of a living host. PLoS Pathogens, 4(6): e1000090. doi:  10.1371/journal.ppat.1000090PMID:18566656Google Scholar


M.H. Moro , O.L. Zegarra-Moro , J. Bjornsson , E.K. Hofmeister , E. Bruinsma , J.J. Germer , and D.H. Persing 2002. Increased arthritis severity in mice coinfected with Borrelia burgdorferi and Babesia microti. The Journal of Infectious Diseases, 186(3): 428–431. PMID: 12134242 doi:  10.1086/341452Google Scholar


M.G. Morshed , J.D. Scott , K. Fernando , L. Beati , D.F. Mazerolle , G. Geddes , and L.A. Durden 2005. Migratory songbirds disperse ticks across Canada, and first isolation of the Lyme disease spirochete, Borrelia burgdorferi, from the avian tick, Ixodes auritulus. The Journal of Parasitology, 91(4): 780–790. PMID: 17089744 doi: 10.1645/GE-3437.1Google Scholar


M.G. Morshed , J.D. Scott , K. Fernando , G. Geddes , A. McNabb , S. Mak , and L.A. Durden 2006. Distribution and characterization of Borrelia burgdorferi isolates from Ixodes scapularis and presence in mammalian hosts in Ontario, Canada. Journal of Medical Entomology, 43(4): 762–773. PMID: 16892637 doi:  10.1603/0022-2585(2006)43[762:DACOBB]2.0.CO;2Google Scholar


E. Murakami 2009. Tick removal: blister and straw and knot methods [online]. Available from qs [accessed 31 May 2009]. Google Scholar


D.T. Nardelli , S.M. Callister , and R.F. Schell 2008. Lyme arthritis: current concepts and a change in paradigm. Clinical and Vaccine Immunology; CVI, 15(1): 21–34. PMID:18003 815 doi: 10.1128/CVI.00330-07Google Scholar


G. Neelakanta , X. Li , U. Pal , X. Liu , D.S. Beck , K. DePonte , et al . 2007. Outer surface protein B is critical for Borrelia burgdorferi adherence and survival within Ixodes ticks. PLoS Pathogens, 3(3): e33. doi: 10.1371/journal.ppat.0030033 PMID:17352535Google Scholar


L.E. Nigrovic , and K.M. Thompson 2007. The Lyme vaccine: a cautionary tale. Epidemiology and Infection, 135(1): 1–8. PMID: 16893489 doi:  10.1017/S0950268806007096Google Scholar


L.E. Nigrovic , A.D. Thompson , A.M. Fine , and A. Kimia 2008. Clinical predictors of Lyme disease among children with a peripheral facial palsy at an emergency department in a Lyme disease-endemic area. Pediatrics, 122(5): e1080–e1085. doi: 10.1542/peds.2008-1273 PMID:18931 349. Google Scholar


H. Noda , U.G. Munderloh , and T.J. Kurtti 1997. Endosymbionts of ticks and their relationship to Wolbachia spp. and tick-borne pathogens of humans and animals. Applied and Environmental Microbiology, 63(10): 3926–3932 PMID:9327557. Google Scholar


S.J. Norris 2006. Antigenic variation with a twist — the Borrelia story. Molecular Microbiology, 60(6): 1319–1322 PMID:16796669 doi: 10.1111/J.1365-2958.2006.05204.xGoogle Scholar


G.H.F. Nuttall , and C. Warburton 1911. Ixodidae. Section II. The genus Ixodes. In Ticks. A monograph of the Ixodoidea. Part II. Edited by G.H.F. Nuttall , C. Warburton , W. F. Cooper , and L.E. Robinson . Cambridge University Press, London, United Kingdom, pp. 133–293. Google Scholar


N.H. Ogden , L. Trudel , H. Artsob , I.K. Barker , G. Beauchamp , D.F. Charron , et al. 2006. Ixodes scapularis ticks collected by passive surveillance in Canada: analysis of geographic distribution and infection with Lyme borreliosis agent Borrelia burgdorferi. Journal of Medical Entomology, 43(3): 600–609. PMID: 16739422 doi: 10.1603/0022-2585(2006)43[600:ISTCBP]2.0.CO;2Google Scholar


N.H. Ogden , H. Artsob , L.R. Lindsay , and P.N. Sockett 2008a. Lyme disease: a zoonotic disease of increasing importance to Canadians. Canadian Family Physician, 54(10): 1381–1384 PMID: 18854461. Google Scholar


N.H. Ogden , M. Bigras-Poulin , K. Hanincová , A. Maarouf , C.J. O'Callaghan , and K. Kurtenbach 2008b. Projected effects of climate change on tick phenology and fitness of pathogens transmitted by the North American tick Ixodes scapularis. Journal of Theoretical Biology, 254(3): 621–632. PMID:18634803 doi: 10.1016/j.jtbi.2008.06.020Google Scholar


N.H. Ogden , L.R. Lindsay , K. Hanincová , I.K. Barker , M. Bigras-Poulin , D.F. Charron , et al . 2008c. Role of migratory birds in introduction and range expansion of Ixodes scapularis ticks and of Borrelia burgdorferi and Anaplasma phagocytophilum in Canada. Applied and Environmental Microbiology, 74(6): 1780–1790. PMID:18245258 doi: 10.1128/AEM.01982-07Google Scholar


N.H. Ogden , L.R. Lindsay , M. Morshed , P.N. Sockett , and H. Artsob 2008d. The rising challenge of Lyme borreliosis in Canada. Canada Communicable Disease Report, 34(1): 1–19. PMID: 18290267-19. Google Scholar


J. Oksi , M. Marjamäki , J. Nikoskelainen , and M.K. Viljanen 1999. Borrelia burgdorferi detected by culture and PCR in clinical relapse of disseminated Lyme borreliosis. Annals of Medicine, 31(3): 225–232. PMID: 10442678 doi: 10.3109/07853899909115982Google Scholar


J.H. Oliver Jr. 1989. Biology and systematics of ticks (Acari: Ixodida). Annual Review of Ecology and Systematics, 20(1): 397–430. doi:  10.1146/ Scholar


Z. Ouyang , M. He , T. Oman , X.F. Yang , and M.V. Norgard 2009. A manganese transporter, BB0219 (BmtA), is required for virulence by the Lyme disease spirochete, Borrelia burgdorferi. Proceedings of the National Academy of Sciences of the United States of America, 106(9): 3449–3454. doi: 10.1073/pnas.0812999106 PMID: 19218460. Google Scholar


D.C. Owen 2006. Is Lyme disease always poly microbial? — The jigsaw hypothesis. Medical Hypotheses, 67(4): 860–864 PMID: 16814477 doi: 10.1016/j.mehy.2006.03.046Google Scholar


A.R. Pachner , J. Basta , E. Delaney , and D. Hulinska 1995. Localization of Borrelia burgdorferi in murine Lyme borreliosis by electron microscopy. The American Journal of Tropical Medicine and Hygiene, 52(2): 128–133 PMID:7872439. Google Scholar


A.R. Pachner , D. Dail , L. Li , L. Gurey , S. Feng , E. Hodzic , and S. Barthold 2002. Humoral immune response associated with Lyme borreliosis in nonhuman primates: analysis by immunoblotting and enzyme-linked immunosorbent assay with sonicates or recombinant proteins. Clinical and Diagnostic Laboratory Immunology, 9(6): 1348–1355 PMID:12414773. Google Scholar


U. Pal , P. Wang , F. Bao , X. Yang , S. Samanta , R. Schoen , et al . 2008. Borrelia burgdorferi basic membrane proteins A and B participate in the genesis of Lyme arthritis. The Journal of Experimental Medicine, 205(1): 133–141. PMID:18166 585 doi: 10.1084/jem.20070962Google Scholar


H.W. Pfister , K. Einhäupl , V. Preac-Mursic , B. Wilske , and G. Schierz 1984. The spirochetal etiology of lymphocytic meningoradiculitis of Bannwarth (Bannwarth's syndrome). Journal of Neurology, 231(3): 141–144 PMID:6481420 doi:  10.1007/BF00313682Google Scholar


J.D. Piacentino , and B.S. Schwartz 2002. Occupational risk of Lyme disease: an epidemiological review. Occupational and Environmental Medicine, 59(2): 75–84. PMID: 11850549 doi:  10.1136/oem.59.2.75Google Scholar


J.E. Posey , and F.C. Gherardini 2000. Lack of a role for iron in the Lyme disease pathogen. Science (Washington, D.C.), 288(5471): 1651–1653. PMID: 10834845 doi: 10.1126/science.288.5471.1651Google Scholar


D. Postic , M. Gamier , and G. Baranton 2007. Multilocus sequence analysis of atypical Borrelia burgdorferi sensu lato isolates — description of Borrelia californiensis sp. nov., and genomospecies 1 and 2. International Journal of Medical Microbiology, 297(4): 263–271 PMID: 17374507 doi: 10.1016/j.ijmm.2007.01.006Google Scholar


W.G. Qiu , J.F. Bruno , W.D. McCaig , Y. Xu , L. Livey, M.E. Schriefer , and B.J. Luft 2008. Wide distribution of a high-virulence Borrelia burgdorferi clone in Europe and North America. Emerging Infectious Diseases, 14(7): 1097–1104. PMID:18598631 doi: 10.3201/eid1407.070880Google Scholar


N. Ramamoorthi , S. Narasimhan , U. Pal , F. Bao , X.F. Yang , D. Fish , et al. 2005. The Lyme disease agent exploits a tick protein to infect the mammalian host. Nature (London), 436(7050): 573–577. PMID:16049492 doi: 10.1038/nature03812Google Scholar


R.A. Rawling , K. Strouse , and P.A. Granato 2009. Borrelia burgdorferi and Babesia microti coinfection in a 79-year-old camper. Clinical Microbiology Newsletter, 31(5): 37–39. doi:  10.1016/j.clinmicnews.2009.02.002Google Scholar


J.M.C. Ribeiro , and I.M.B. Francischetti 2003. Role of arthropod saliva in blood feeding: sialome and post-sialome perspectives. Annual Review of Entomology, 48(1): 73–88. PMID: 12194906 doi:  10.1146/annurev.ento.48.060402.102812Google Scholar


J. Robertson , E. Guy , N. Andrews , B. Wilske , P. Anda , M. Granström , et al. 2000. A European multicenter study of immunoblotting in serodiagnosis of Lyme borreliosis. Journal of Clinical Microbiology, 38(6): 2097–2102 PMID: 10834959. Google Scholar


P.A. Rosa , K. Tilly , and P.E. Stewart 2005. The burgeoning molecular genetics of the Lyme disease spirochaete. Nature Reviews Microbiology, 3(2): 129–143. PMID: 15685224 doi:  10.1038/nrmicro1086Google Scholar


C.D. Rosé , P.T. Fawcett , and K.M. Gibney 2001. Arthritis following recombinant outer surface protein A vaccination for Lyme disease. The Journal of Rheumatology, 28(11): 2555–2557 PMID: 11708435. Google Scholar


N. Rudenko , M. Golovchenko , L. Grubhoffer , and J.H. Oliver Jr. 2009. Borrelia carolinensis sp. nov., a new (14th) member of the Borrelia burgdorferi sensu lato complex from the southeastern region of the United States. Journal of Clinical Microbiology, 47(1): 134– 141. PMID:19020062 doi: 10.1128/JCM.0118 3-08Google Scholar


T.A. Rupprecht , U. Koedel , V. Fingerle , and H.-W. Pfister 2008. The pathogenesis of Lyme neuroborreliosis: from infection to inflammation. Molecular Medicine (Cambridge, Mass.), 14(3–4): 205–212 PMID: 18097481. Google Scholar


A.J. Saah , and D.R. Hoover 1997. “Sensitivity” and “specificity” reconsidered: the meaning of these terms in analytical and diagnostic settings. Annals of Internal Medicine, 126(1): 91–94 PMID:8992938. Google Scholar


D.J. Salkeld , S. Leonhard , Y.A. Girard , N. Hahn , J. Mun , K.A. Padgett , and R.S. Lane 2008. Identifying the reservoir hosts of the Lyme disease spirochete Borrelia burgdorferi in California: the role of the western gray squirrel (Sciurus griseus). The American Journal of Tropical Medicine and Hygiene, 79(4): 535–540 PMID: 18840740. Google Scholar


B.S. Schneider , M.E. Schriefer , G. Dietrich , M.C. Dolan , M.G. Morshed , and N.S. Zeidner 2008. Borrelia bissettii isolates induce pathology in a murine model of disease. Vector-Borne and Zoonotic Diseases (Larchmont, N.Y.), 8(5): 623–633. PMID: 18454594 doi: 10.1089/vbz.2007.0251Google Scholar


H. Schroeder , P.J. Skelly , P.F. Zipfel , B. Losson , and A. Vanderplasschen 2009. Subversion of complement by hematophagous parasites. Developmental and Comparative Immunology, 33(1): 5–13. PMID:18762211 doi: 10.1016/j.dci.2008.07.010Google Scholar


T.J. Schuijt , J.W.R. Hovius , N.D. van Burgel , N. Ramamoorthi , E. Fikrig , and A.P. van Dam 2008. The tick salivary protein Salp15 inhibits the killing of serum-sensitive Borrelia burgdorferi sensu lato isolates. Infection and Immunity, 76(7): 2888–2894. PMID: 18426890 doi:  10.1128/IAI.00232-08Google Scholar


T.G. Schwan , J. Piesman , W.T. Golde , M.C. Dolan , and P.A. Rosa 1995. Induction of an outer surface protein on Borrelia burgdorferi during tick feeding. Proceedings of the National Academy of Sciences of the United States of America, 92(7): 2909–2913. PMID:7708747 doi: 10.1073/pnas.92.7.2909Google Scholar


T.G. Schwan , S.J. Raffel , M.E. Schrumpf , and S.F. Porcella 2007. Diversity and distribution of Borrelia hermsii. Emerging Infectious Diseases, 13(3): 436–442 PMID: 17552097. Google Scholar


G.A. Scoles , A.B. Broce , T.J. Lysyk , and G.H. Palmer 2005. Relative efficiency of biological transmission of Anaplasma marginale (Rickettsiales: Anaplasmataceae) by Dermacentor andersoni (Acari: Ixodidae) compared with mechanical transmission by Stomoxys calcitrans (Diptera: Muscidae). Journal of Medical Entomology, 42(4): 668–675. PMID: 16119558 doi: 10.1603/0022-2585(2005)042[0668:REOBTO]2.0.CO;2Google Scholar


J.D. Scott , K. Fernando , S.N. Banerjee , L.A. Durden , S.K. Byrne , M. Banerjee , R.B. Mann , and M.G. Morshed 2001. Birds disperse ixodid (Acari: Ixodidae) and Borrelia burgdorferi-infected ticks in Canada. Journal of Medical Entomology, 38(4): 493–500 PMID: 11476328. Google Scholar


J.D. Scott , M.-K. Lee , K. Fernando , D.R. Jorgensen , L.A. Durden , and M.G. Morshed 2008. Rapid introduction of Lyme disease spirochete, Borrelia burgdorferi sensu stricto, in Ixodes scapularis (Acari: Ixodidae) established at Turkey Point Provincial Park, Ontario, Canada. Journal of Vector Ecology, 33(1): 64–69. PMID:18697308 doi: 10.3376/1081-1710(2008)33[64:RIOLDS]2.0.CO;2Google Scholar


B.M. Shariat , J.A. Freimund , S.M. Wright , C.S. Murphree , and J.T. Thomas 2007. Borrelia infection rates in winter ticks (Dermacentor albipictus) removed from white-tailed deer (Odocoileus virginianus) in Cheatham County, Tennessee. Journal of the Tennessee Academy of Science, 82: 57–61. Google Scholar


Y. Shi , Q. Xu , K. McShan , and F.T. Liang 2008. Both decorin-binding proteins A and B are critical for the overall virulence of Borrelia burgdorferi. Infection and Immunity, 76(3): 1239–1246. PMID:18195034 doi: 10.1128/IAI.00897-07Google Scholar


L.H. Sigal , and A.L. Hassett 2002. Contributions of societal and geographical environments to “chronic Lyme disease”: the psychopathogenesis and aporology of a new “medically unexplained symptoms” syndrome. Environmental Health Perspectives, 110(Supplement 4): 607–611 PMID:12194894. Google Scholar


S.K. Singh , and H.J. Girschick 2004. Lyme borreliosis: from infection to autoimmunity. Clinical Microbiology and Infection, 10(7): 598–614. PMID:15214872 doi: 10.1111/j.1469-0691.2004.00895.xGoogle Scholar


B.H. Skogman , S. Croner , M. Nordwall , M. Eknefelt , J. Ernerudh , and P. Forsberg 2008. Lyme neuroborreliosis in children: a prospective study of clinical features, prognosis, and outcome. The Pediatric Infectious Disease Journal, 27(12): 1089–1094. PMID: 19008771 doi:  10.1097/INF.0b013e31817fd423Google Scholar


T.J. Slowik , and R.S. Lane 2009. Feeding preferences of the immature stages of three western North American ixodid ticks (Acari) for avian, reptilian, or rodent hosts. Journal of Medical Entomology, 46(1): 115–122. PMID: 19198525 doi:  10.1603/033.046.0115Google Scholar


R.P. Smith Jr. , S.B. Muzaffar , J. Lavers , E.H. Lacombe , B.K. Cahill , C.B. Lubelczyk , et al. 2006. Borrelia garinii in seabird ticks (Ixodes uriae), Atlantic coast, North America. Emerging Infectious Diseases, 12(12): 1909–1912 PMID: 17326943. Google Scholar


F.A.H. Sperling , and A.M. Roe 2009. Molecular dimensions of insect taxonomy. In Insect biodiversity: science and society. Edited by R.G. Foottit and P.H. Adler . Blackwell Publishing, Oxford, United Kingdom. Google Scholar


A.C. Steere 1989. Lyme disease. The New England Journal of Medicine, 321(9): 586–596 PMID:26 68764. Google Scholar


A.C. Steere , G. McHugh , N. Damle , and V.K. Sikand 2008. Prospective study of serologic tests for Lyme disease. Clinical Infectious Diseases, 47(2): 188–195. PMID:18532885 doi: 10.1086/589242Google Scholar


B. Stevenson , K. von Lackum , S.P. Riley , A.E. Cooley , M.E. Woodman , and T. Bykowski 2006. Evolving models of Lyme disease spirochete gene regulation. Wiener Klinische Wochenschrift, 118(21–22): 643–652. PMID:17 160602 doi:  10.1007/s00508-006-0690-2Google Scholar


R.K. Straubinger 2000. Lyme borreliosis in dogs. In Recent advances in canine infectious diseases. Edited by L.E. Carmichael . International Veterinary Information Service, Ithaca, New York. Google Scholar


R.B. Stricker , and L. Johnson 2008. Serologic tests for Lyme disease: more smoke and mirrors. Clinical Infectious Diseases, 47(8): 1111–1112, author's reply 1112–1113. PMID:18800935 doi: 10.1086/592121Google Scholar


E.Y. Stromdahl , P.C. Williamson , T.M. Kollars , S.R. JrEvans , R.K. Barry , M.A. Vince , and N.A. Dobbs 2003. Evidence of Borrelia lonestari DNA in Amblyomma americanum (Acari: Ixodidae) removed from humans. Journal of Clinical Microbiology, 41(12): 5557–5562. PMID: 14662 940 doi:  10.1128/JCM.41.12.5557-5562.2003Google Scholar


P.J. Suffridge , B.R. Smoller , and P.R. Carrington 1999. Spiders and Borrelia burgdorferi: no evidence of reservoir occurrence in central Arkansas. International Journal of Dermatology, 38(4): 296–297. PMID: 10321947 doi:  10.1046/j.1365-4362.1999.00602.xGoogle Scholar


B.A. Summers , A.F. Straubinger , R.H. Jacobson , Y.F. Chang , M.J. Appel , and R.K. Straubinger 2005. Histopathological studies of experimental Lyme disease in the dog. Journal of Comparative Pathology, 133(1): 1–13. PMID: 15904927 doi:  10.1016/j.jcpa.2004.11.006Google Scholar


D. Terekhova , R. Iyer , G.P. Wormser , and I. Schwartz 2006. Comparative genome hybridization reveals substantial variation among clinical isolates of Borrelia burgdorferi sensu stricto with different pathogenic properties. Journal of Bacteriology, 188(17): 6124–6134. PMID: 16923879 doi:  10.1128/JB.00459-06Google Scholar


D.D. Thomas , D. Cadavid , and A.G. Barbour 1994. Differential association of Borrelia species with cultured neural cells. The Journal of Infectious Diseases, 169(2): 445–448 PMID:810 6781. Google Scholar


C.D. Tibbies , and J.A. Edlow 2007. Does this patient have erythema migrans? Journal of the American Medical Association, 297(23): 2617–2627. doi: 10.1001/jama.297.23.2617Google Scholar


K. Tilly , A. Bestor , M.W. Jewett , and P. Rosa 2007. Rapid clearance of Lyme disease spirochetes lacking OspC from skin. Infection and Immunity, 75(3): 1517–1519. PMID: 17158906 doi:  10.1128/IAI.01725-06Google Scholar


K. Tilly , P.A. Rosa , and P.E. Stewart 2008. Biology of infection with Borrelia burgdorferi. Infectious Disease Clinics of North America, 22(2): 217–234., v PMID:18452798 doi: 10.1016/j.idc.2007.12.013Google Scholar


Y. Tourand , J. Deneke , T.J. Moriarty , and G. Chaconas 2009. Characterization and in vitro reaction properties of 19 unique hairpin telomeres from the linear plasmids of the Lyme disease spirochete. The Journal of Biological Chemistry, 284(11): 7264–7272. PMID:19122193 doi: 10.1074/jbc.M808918200Google Scholar


A.J. Ullmann , R.S. Lane , K. Kurtenbach , M. Miller , M.E. Schriefer , N. Zeldner , and J. Piesman 2003. Bacteriolytic activity of selected vertebrate sera for Borrelia burgdorferi sensu stricto and Borrelia bissettii. Journal of Parasitology, 89(6): 1256–1257. PMID:14740924 doi: 10.1645/Ge-3081RNGoogle Scholar


D. Vanousová , and J. Hercogová 2008. Lyme borreliosis treatment. Dermatologie Therapy, 21(2): 101–109. PMID:18394084 doi: 10.1111/J.1529-8019.2008.00177.xGoogle Scholar


L. van Overbeek , F. Gassner , C.L. van der Pias , P. Kastelein , U. Nunes-da Rocha , and W. Takken 2008. Diversity of Ixodes ricinus tick-associated bacterial communities from different forests. FEMS Microbiology Ecology, 66(1): 72–84. PMID:18355299 doi:  10.1111/j.1574-6941.2008.00468.xGoogle Scholar


M. Vázquez , C. Muehlenbein , M. Cartter , E.B. Hayes , S. Ertel , and E.D. Shapiro 2008. Effectiveness of personal protective measures to prevent Lyme disease. Emerging Infectious Diseases, 14(2): 210–216. PMID:18258112 doi: 10.3201/eid1402.070725Google Scholar


J. Welsh , C. Pretzman , D. Postic , I. Saint Girons , G. Baranton , and M. McClelland 1992. Genomic fingerprinting by arbitrarily primed polymerase chain reaction resolves Borrelia burgdorferi into three distinct phyletic groups. International Journal of Systematic Bacteriology, 42(3): 370–377 PMID: 1503971. Google Scholar


D.M. Wesson , D.K. McLain , J.H. Oliver , J. Piesman , and F.H. Collins 1993. Investigation of the validity of species status of Ixodes dammini (Acari: Ixodidae) using rDNA. Proceedings of the National Academy of Sciences of the United States of America, 90(21): 10221–10225. PMID:8234280 doi: 10.1073/pnas.90.21.10221Google Scholar


H. Whitney 2005. Lyme Disease in Newfoundland. Animal Health Fact Sheet AP053, Newfoundland and Labrador Department of Agriculture, St. John's, Newfoundland. Google Scholar


B. Wilske , V. Fingerle , and U. Schulte-Spechtel 2007. Microbiological and serological diagnosis of Lyme borreliosis. FEMS Immunology and Medical Microbiology, 49(1): 13–21. PMID: 17266710 doi: 10.1111/j.1574-695X.2006.00139.xGoogle Scholar


J.M. Wilson 2007. Concerns regarding the Infectious Diseases Society of America Lyme disease clinical practice guidelines. Clinical Infectious Diseases, 44(8): 1135–1137., author's reply 1137– 1139. PMID:17366466 doi: 10.1086/513030Google Scholar


G.P. Wormser , R.J. Dattwyler , E.D. Shapiro , J.J. Halperin , A.C. Steere , M.S. Klempner , et al. 2006. The clinical assessment, treatment, and prevention of Lyme disease, human granulocytic anaplasmosis, and babesiosis: clinical practice guidelines by the Infectious Diseases Society of America. Clinical Infectious Disease. Clinical Infactious Disease, 45: 1089–1134. Google Scholar


G.P. Wormser , R.J. Dattwyler , E.D. Shapiro , J.J. Halperin , A.C. Steere , M.S. Klempner et al. 2007. Erratum: The clinical assessment, treatment, and prevention of Lyme disease, human granulocytic anaplasmosis, and babesiosis: clinical practice guidelines by the Infectious Diseases Society of America. Clinical Infactious Disease, 45: 941. Google Scholar


G.P. Wormser , D. Liveris , K. Hanincová , D. Brisson , S. Ludin , V.J. Stracuzzi , et al. 2008. Effect of Borrelia burgdorferi genotype on the sensitivity of C6 and 2-tier testing in North American patients with culture-confirmed Lyme disease. Clinical Infectious Diseases, 47(7): 910–914. PMID:18724824 doi: 10.1086/591529Google Scholar


Q. Xu , K. McShan , and F.T. Liang 2008a. Modification of Borrelia burgdorferi to over-produce OspA or VlsE alters its infectious behaviour. Microbiology, 154(Pt 11): 3420– 3429. PMID:18957595 doi: 10.1099/mic.0.2008/019737-0Google Scholar


Y. Xu , J.F. Bruno , and B.J. Luft 2008b. Profiling the humoral immune response to Borrelia burgdorferi infection with protein microarrays. Microbial Pathogenesis, 45(5–6): 403–407. PMID:18976702 doi: 10.1016/j.micpath.2008.09.006Google Scholar


X. Yang , A.S. Coleman , J. Anguita , U. Pal , and J. Coburn 2009. A chromosomally encoded virulence factor protects the Lyme disease pathogen against host-adaptive immunity. PLoS Pathogens, 5(3): e1000326. doi: 10.1371/journal.ppat. 1000326 PMID: 19266024. Google Scholar


H. Yrjänäinen , J. Hytönen , X.Y. Song , J. Oksi , K. Hartiala , and M.-K. Viljanen 2007. Antitumor necrosis factor-alpha treatment activates Borrelia burgdorferi spirochetes 4 weeks after ceftriaxone treatment in C3H/He mice. The Journal of Infectious Diseases, 195(10): 1489–1496. PMID:17436229 doi: 10.1086/513873Google Scholar


A. Žákovská , P. Nejedla , A. Holíková , and Dendis . 2002. Positive findings of Borrelia burgdorferi in Culex (Culex) pipiens pipiens larvae in the surrounding of Brno city determined by the PCR method. Annals of Agricultural and Environmental Medicine, 9(2): 257–259 PMID: 12498597. Google Scholar


A. Žakovska , E. Janouškovcová , K. Pejchalová , J. Halouzka , and M. Dendis 2008. Identification and characterization of 31 isolates of Borrelia burgdorferi (Spirochaetales, Spirochaetaceae) obtained from various hosts and vectors using PCR-RFLP and SDS-PAGE analysis. Acta Parasitologica, 53(2): 186–192. doi: 10.2478/s11686-008-0028-5Google Scholar


L. Zaretsky 2006. Lyme disease in Canada. Canadian Pharmacists Journal, 139(4): 29–32. Google Scholar


J. Zhong , A. Jasinskas , A.G. Barbour , and F. Romesberg 2007. Antibiotic treatment of the tick vector Amblyomma americanum reduced reproductive fitness. PLoS ONE, 2(5): e405. doi:  10.1371/journal.pone.0000405 PMID: 17476327. Google Scholar


[1] 1This series is supported by a fund established in memory of the late Charles P. Alexander. The Entomological Society of Canada uses the fund to support the publication of invited articles or reviews on topics that broaden the scope of The Canadian Entomologist and (or) are of current significance to entomology.

[2] Cette série est financée par un fond établi à la mémoire de feu Charles P. Alexander. La Société d'entomologie du Canada utilise les fonds afin de supporter la publication d'articles ou de revues sur invitation portant sur des sujets qui élargissent le champ de The Canadian Entomologist et (ou) sont présentement pertinents en entomologie.

© 2009 Entomological Society of Canada
Janet L.H. Sperling and Felix A.H. Sperling "Lyme Borreliosis in Canada: Biological Diversity and Diagnostic Complexity from an Entomological Perspective," The Canadian Entomologist 141(6), 521-549, (1 November 2009).
Received: 26 March 2009; Accepted: 1 June 2009; Published: 1 November 2009
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