The phylogenetic relationships of Culicidae native to the northeastern United States were investigated by analyzing small subunit ribosomal DNA (18S rDNA) sequences obtained from 39 species representing nine genera. Molecular phylogenies were consistent with traditional classifications based on morphological characters except for the placements of Psorophora Robineau-Desvoidy and Uranotaenia Lynch Arribalzaga. In our analyses, 1) Anopheles Meigen was strongly supported as the sister taxon to the remaining Culicidae; 2) Toxorhynchites Theobald was represented as a distinct monophyletic sister group to the Culicinae; 3) Psorophora formed a basal clade to Culiseta Felt, Coquillettidia Dyar, and Culex L. but also was shown as a sister taxon to Aedes Meigen and Ochlerotatus Lynch Arribalzaga; 4) Coquillettidia perturbans (Walker) seems to be a sister group to Culiseta; 5) placement of Uranotaenia was inconclusive and seemed to be either a sister group to the Aedes and Ochlerotatus or a basal taxon to all other culicines; and 6) Aedes and Ochlerotatus formed two separate and distinct clades, providing phylogenetic data consistent with the recent elevation of Ochlerotatus to the generic level as proposed by Reinert (2000). The utility of 18S rDNA for evaluating phylogenetic and evolutionary relationships among mosquito taxa was demonstrated at the genus and species levels. To our knowledge, this study represents the first molecular-based phylogenetic study of mosquito species occurring within this geographic region of North America and contains the largest number of species that have been examined among the genera Aedes and Ochlerotatus.

Anopheles halophylus Silva-do-Nascimento & Lourenço-de-Oliveira was recently described using morphological and biological variants in specimens previously identified as Anopheles triannulatus (Neiva & Pinto). Because these two species occur in sympatry in central Brazil, we used allozymes to determine the extent of gene flow to confirm that they are different species. Of 11 allozyme loci analyzed, one (Mpi) was found to be diagnostic for An. halophylus and An. triannulatus, confirming their specific status. This locus revealed a second sibling species within An. triannulatus sensu lato. An. halophylus and the new undescribed species were confirmed using random amplified polymorphic DNA markers that showed moderate genetic divergence among these three sympatric and closely related taxa (D = 0.145–0.428). Moreover, this marker indicates that An. halophylus and the new species are more closely related to each other than either is to An. triannulatus.

Anopheles fluminensis Root is a member of the Arribalzagia Series in the subgenus Anopheles. We report the first record of this species in the department of Cochabamba, Bolivia. This species was sampled from two locations in the foothills of the eastern Andes Mountains within the Chapare Valley. Larvae were collected in fast-flowing, shaded streams at the edges of rocky pools. We provide the first sequence data for the rDNA of An. fluminensis, a partial sequence of the 5.8S and the internal transcribed spacer 2 (ITS2). The ITS2 of An. fluminensis, sequenced from two individuals at one site, was at least 596 bp, had 56.5% GC, and included three large repeats (≈125 bp each). We describe a polymerase chain reaction protocol and species-specific primers for identifying this species in the Chapare Valley, Bolivia.

Diurnal activity of host-seeking “canyon flies” (Fannia benjamini complex) (Diptera: Muscidae) was determined on a warm, sunny day during their peak seasonal activity period (early July) in the coastal mountain community of La Habra Heights in Los Angeles County, California. High levels of activity persisted for several hours in the morning and evening, but peak abundance was within an hour after sunrise and an hour before sunset, when >600 flies (mainly Fannia conspicua Malloch) could be collected in 5 min from a person using a sweep net. Host-seeking activity was low during midday hours, when flies apparently were seeking shelter from the heat, and activity ceased after sunset. Potential bait materials, including some known to elicit a response by other host-seeking Diptera (water, rabbit feces, egg bait, milk bait, Limburger cheese, ethanol, and CO₂) were tested for “canyon fly” response using CDC-type suction traps (without light). CO₂ resulted in significantly higher capture of female “canyon flies” (up to ≈2,000 flies per trap in a 6-h period) relative to traps baited with other materials or with no bait. Host-seeking activity in relation to distance from a putative developmental site was evaluated. The proportional capture of flies in CO₂-baited suction traps was significantly explained by distance from a residential area planted with Aptenia cordifolia (L.) (Aizoaceae; red apple), a ground cover plant that is a developmental site for F. conspicua. Proportional trap capture rapidly decreased as distance from the residential area increased. Implications of these studies for “canyon fly” control are discussed.

Sampling indoor resting African malaria vectors is traditionally done by hand catches with oral or mechanical aspirators and pyrethrum spray catches (PSCs). In this study, we designed and briefly evaluated an inexpensive but practical alternative by using a cloth resting box or wicker resting basket and a ceiling net. Evaluations were performed in greenhouse and field situations in rural Kenya by comparing capture rates of Anopheles gambiae s.l. and Anopheles funestus (Giles) in these traps to hand collections and PSCs. A resting box and a ceiling net when used together collected more mosquitoes than a single collector using a hand-held aspirator but only one-third the number collected by PSCs. At sites where PSCs are impractical, a resting box and ceiling net can be effectively used as an alternative to hand catches in malaria surveillance.

The M and S molecular forms of Anopheles gambiae sensu stricto Giles are thought to be reproductively isolated through premating barriers. However, the exact mechanisms of recognition of conspecific partners are unknown. Because mating in An. gambiae occurs in swarms, one might expect swarming behavior between the M and S forms to be different and that this probably reduces the risk of contact between males and females of the different forms in areas where they are sympatric. We report the occurrence of four mixed swarms, containing males of M and S forms, out of a total of 26 swarms sampled in Soumousso, a typical savannah village of Burkina Faso, West Africa. However, the frequency of mixed swarms was lower than that expected by chance. This observation suggests partial segregation between the swarms of the molecular forms, which may contribute to their isolation. Because the frequency of mixed swarms seems too high to explain the low frequency of cross-mating and hybrids, we suggest that mate recognition in a swarm is more important than swarm segregation.

We investigated the effects of environmental factors and immature density on the productivity of Aedes aegypti (L.) and explored the hypothesis that immature populations were under nutritional stress. In total, 1,367 containers with water in 624 premises were studied in Salinas, southern Puerto Rico (May–July 2004). We counted 3,632 pupae, and most female pupae (70%) were in five of 18 types of containers. These containers were unattended and influenced by local yards’ environmental conditions. Pupal productivity was significantly associated with the number of trees per premise, water volume, and lower water temperatures. Larval and pupal abundance were larger in containers with leaf litter or algae. Pupal productivity and biomass of emerging females varied in containers with litter of different tree species. We found a significant and positive association between numbers of larvae and pupae of Ae. aegypti and a negative relationship between larval density and mass of emerging females. From multivariate analyses, we interpreted that 1) food limitation or competition existed in a number of containers; and 2) to a lesser extent, there was lack of negative larval density effects in containers with a larger water volume and lower temperature, where emerging females were not under nutritional stress. Corroborating evidence for food limitation or intraspecific competition effects came from our observations that females emerging in the field had an average body mass comparable with those females produced in the laboratory with the lowest feeding regime. Ae. aegypti larvae in Salinas are most likely influenced by resource limitation or competition and by rainfall in unmanaged containers in the absence of aquatic predators. Source reduction and improved yard management targeting unattended containers would eliminate most Ae. aegypti productivity and removal or control of shaded, larger containers would eliminate the production of the largest emerging mosquito females in the study area.

Natural selection should favor females that oviposit in sites providing the best available conditions for her progeny. In temporary pools, two important conditions include risk of desiccation and risk of predation to larvae. In an artificial pool experiment, we compared oviposition responses of two dipterans, Culiseta longiareolata Macquart (Culicidae) and Chironomus riparius Meigan (Chironomidae), in very shallow pools that, if left to dry, would not have had a long enough hydroperiod for larvae to complete development, versus deeper pools that would have a sufficiently long enough hydroperiod for development. Water depth was crossed with the presence or absence of the predatory backswimmer Notonecta maculata F. (Hemiptera: Notonectidae). Oviposition patterns were consistent with larval vulnerability of the two species to predation by N. maculata. C. longiareolata, whose larvae are highly vulnerable to predation, strongly avoided ovipositing in pools containing this predator, whereas C. riparius, whose larvae are considerably less vulnerable, did not display oviposition avoidance. Pool depth did not affect oviposition habitat selection in either dipteran.

Anopheles gambiae s.s. Giles accepted a range of agarose gels, varying from 0.5 to 8% (wt:vol), for oviposition; laid more eggs on 0.5% agarose gels than on moist filter paper or on drier agarose; and laid equal numbers of eggs on 0.5% agarose gels and distilled water. Larvae hatched on agarose gel substrates and crawled onto the surface of moist agarose gels, but they tended only to burst the egg cap and remain within the egg case on drier gels. A mixture of cultured bacteria, originating from a natural larval habitat of An. gambaiae s.s. in western Kenya, was classified by 16S rDNA sequence analysis, and then this mixture or individual colonies from it was used as odor sources in ovipositional experiments with agarose substrates. Of 61 sequences from a mixed clone sequence library, most (78%) were Pseudomonas strains, whereas the remainder were Stenotrophomonas, Enterobacter, Pantoea, Klebsiella, Acinetobacter, Aeromonas, and Bacillus. Oviposition was significantly reduced when mixtures of bacterial colonies of these strains, or a lawn of colonies of a field isolate of S. maltophilia, was presented. Oviposition was neither reduced nor enhanced when field isolates of Pseudomonas putida or Pseudomonas alcaligenes colonies were presented. These results suggest that gravid An. gambiae females are sensitive to bacterial-derived odors emanating from cultured bacteria from natural larval habitats and that some bacterial odors may be repellent.

In total, 2,408 primary school girls (6–14 yr old) in two districts within the Gaza Governorate were examined for the presence of head lice, Pediculus humanus capitis De Geer. The localities chosen for the study were the Old Gaza city and the rural village Jabalia. The rate of infestation with lice was 14.1%, and an additional 35% of girls had nits (eggs) only. The prevalence of louse infestation was high among the 6–12-yr-old girls. A sharp decline in infestation was observed after 12 yr of age. No lice were found on the 13 to 14-yr-old girls examined. Approximately 67.1% of infested girls had one to 10 lice and 49.8% had one to 10 nits on their hair. Significant difference in louse and nit only infestations was found between girls with short and long hair.

The complete 18S rDNA and internal transcribed spacer (ITS)-2 rDNA sequences were obtained from Anopheles atroparvus Van Thiel and Anopheles plumbeus Stephens from two areas of Spain. The number of nucleotide differences in the 18S rDNA of the two species is high compared with differences in the same gene of other invertebrate vectors. In Anopheles, short 18S rDNA sequences are richer in AT than the longer sequences, which are richer in GC and include extremely GC-biased expanded regions. Four small regions in the variable regions V4 and V7 contain the majority of nucleotide differences. The results did not support the use of partial sequences for relationship analyses. Genetic distances and phylogenetic analyses supported the most recent classification of Anopheles. The complete 18S rDNA sequence is better for studying anopheline phylogenetics.

Repellents play an important role in protecting humans from the bites of insect pests. An effective and safe repellent will be useful in reducing human-vector contact and thereby help in the interruption of vector borne disease transmission. Because of the unavailability of m-toluic acid in India for the manufacture of N,N-diethyl m-toluamide (DEET), there is a need to develop an alternate effective and safe insect repellent. In total, 120 substituted amides were synthesized and tested for repellency at 1.0 mg/cm² under laboratory conditions. Among these amides, N,N-diethyl phenylacetamide (DEPA), applied at 1.0 mg/cm² in different oil bases, was found to exhibit promising repellency (6–8 h) in the laboratory when tested against Aedes aegypti (L.) The repellent DEPA was evaluated on army personnel in comparison with dimethylphthalate (DMP) and DEET against mosquitoes, black flies, and land leeches under field condition in the North-East Frontier area of India. Both DEPA and DEET displayed broad-spectrum repellency. DEPA was more effective than DMP against all test organisms. However, no significant difference was noticed between DEPA and DEET for repellency at 0.25 and 0.5 mg/cm² against black flies and mosquitoes. DMP was the least effective among the three compounds in the field studies. The relative potency of DEPA in comparison with DEET and DMP for repellency against Phlebotomine sand flies also was determined. At 0.1 mg/cm², both DEPA and DEET were found to be equally effective with a protection time from 4.37 ± 0.08 to 4.45 ± 0.15 h. Both compounds were significantly more effective than DMP. At 0.2 mg/cm², DEPA and DEET provided protection times of 6.52 ± 0.08 and 7.15 ± 0.15 h, respectively. DEPA was formulated into a vanishing cream, a pharmacologically safe polymer-based liquid, and a liposphere lotion. The vanishing cream and the two-polymer liquid formulations enhanced protection times from 4.4 to 6.5 and 7.13 h, respectively, compared with an alcohol solution applied at 0.5 mg/cm² on the forearm of human volunteers. Formulations of DEPA and DEET applied at 0.5 mg/cm² on rabbits exposed to Ae. aegypti enhanced protection times compared with an alcohol solution and the liposphere lotion from 4.0 to 6.0 h and 4.0 to 5.0 h, respectively. Comparison of mean protection times of DEET and DEPA applied at a rate of 0.3 mg/cm² to human volunteers exposed to Cx. quinquefasciatus under field conditions indicated that the lotion formulations of DEET and DEPA provided significantly (Duncan’s multiple-range test, P < 0.05) higher protection times than did alcohol solutions. Toxicological studies revealed that DEPA is safe.

Evaluation of candidate acaricides in livestock or companion animals is expensive, time-consuming, and usually requires large quantities of test material. To identify promising substances at the earliest possible stage of the development process, robust and predictive surrogate animal models, capable of rapidly characterizing potency with minimal compound requirements, are necessary. The objective of this study was to generate an in vivo surrogate animal bioassay capable of rapidly and accurately predicting the topical activity of acaricides emerging from in vitro acaricide bioassays. The rat acaricide test (RAT) requires adult rats, Rattus norvegicus (Berkenhout, 1769), a flexible tick containment device fastened to their dorso-thoracic region, and the nymphal stage of the lone star tick, Amblyomma americanum (L.). The feeding kinetics of A. americanum nymphs on rats was assessed, and compound efficacies were determined by measuring tick survivorship and engorgement weight on acaricide-treated animals. Results from this bioassay demonstrated efficacy with fipronil, ivermectin, permethrin, and chlorpyrifos, and dose–response relationships for each acaricide were determined. The rank order of potencies was fipronil > ivermectin > chlorpyrifos = permethrin for nymphal mortality and fipronil > ivermectin > chlorpyrifos > permethrin for inhibition of nymphal engorgement. The activity of permethrin against nymphs in the RAT was positively correlated with potency values for technical and commercial permethrin formulations against adult A. americanum infestations on cattle. The RAT proved to be an economical, rapid surrogate animal bioassay that together with the in vitro acaricide bioassay can be used for the rapid identification, characterization, and prioritization of candidate acaricides.

Head lice, Pediculis capitis De Geer, populations were investigated for permethrin and malathion resistance after initial establishment of a discriminating dose of topical application bioassay with body lice, Pediculus humanus L. For both insecticides, ≈2 times the lethal dose (LD)₉₅ at 4 h was selected, 2 ng of permethrin and 100 ng of malathion per head louse, respectively. Head lice were collected from heads of infested children in Denmark at 33 primary schools, one kindergarten, and seven boarding schools. The lice were collected by combing of dry hair, with a fine-toothed antilouse comb attached to a vacuum cleaner. A resistance survey covers head lice collected from 208 of 1,441 persons combed. The frequency of permethrin- and malathion-resistant head lice is high in Danish head lice populations. In 17 of 24 samples tested for permethrin resistance, all head lice survived the discriminating dose. Six samples had between 3 and 25% dead head lice, whereas one sample had 60% mortality. In nine of 25 samples tested for malathion resistance, all head lice survived the discriminating dose. Seven samples had <25% dead head lice, and four samples had a mortality of 50% or more at the discriminating dose. The connection between permethrin resistance and kdr-like mutations is confirmed by our findings. The frequency of the double mutation T929I-L932 F in the voltage-sensitive sodium channel gene associated with permethrin resistance was 0.95 in Danish head lice populations.

Sarcoptes scabiei (De Geer) mites burrow in the nonliving stratum corneum of the epidermis of their mammalian hosts. These mites ingest extracellular fluid (serum) that seeps into the burrow from the lower vascular dermis. A strong host antibody response occurs when mites die in the skin. This suggests internal immunogenic proteins are released into the host at this time. Vaccination with internal antigens may be an approach to protect against this mite if host antibody to internal antigens that regulate key physiological processes is ingested along with serum. Our study clearly showed that scabies mites ingest host immunoglobulin as evidenced by the localization of fluorescent-labeled antibody to host immunoglobulin in the anterior midgut and esophagus of fresh mites removed from the host. This is the first study that demonstrates that this nonblood-feeding ectoparasitic mite ingests host antibody while feeding on tissue fluid that seeps into the stratum corneum.

Aedes albopictus (Skuse) (Diptera: Culicidae) is a major nuisance mosquito and a potential arbovirus vector. The host-feeding patterns of Ae. albopictus were investigated during the 2002 and 2003 mosquito seasons in suburban neighborhoods in Wake County, Raleigh, NC. Hosts of blood-fed Ae. albopictus (n = 1,094) were identified with an indirect enzyme-linked immunosorbent assay, by using antisera made in New Zealand White rabbits to the sera of animals that would commonly occur in peridomestic habitats. Ae. albopictus fed predominantly on mammalian hosts (83%). Common mammalian hosts included humans (24%), cats (21%), and dogs (14%). However, a notable proportion (7%) of bloodmeals also was taken from avian hosts. Some bloodmeals taken from birds were identified to species by a polymerase chain reaction-heteroduplex assay (PCR-HDA). Ae. albopictus fed predominantly on chickens and a northern cardinal. PCR-HDA failed to produce detectable products for 29 (58%) of 50 bloodmeals for which DNA had been amplified, indicating that these mosquitoes took mixed bloodmeals from avian and nonavian hosts. Ae. albopictus preference for humans, dogs, and cats was determined by calculating host-feeding indices for the three host pairs based on the proportion of host specific blood-fed mosquitoes collected in relation to the number of specific hosts per residence as established by a door-to-door survey conducted in 2003. Estimates of the average amount of time that residents and their pets (cats and dogs) spent out of doors were obtained. Host-feeding indices based only on host abundance indicated that Ae. albopictus was more likely to feed on domestic animals. However, when feeding indices were time-weighted, Ae. albopictus fed preferentially upon humans. Ae. albopictus blood feeding on humans was investigated using a STR/PCR-DNA profiling technique that involved amplification of three short tandem repeats loci. Of 40 human bloodmeals, 32 (80%) were from a single human, whereas eight (20%) were multiple bloodmeals taken from more than one human host. We conclude that the blood-feeding preference of Ae. albopictus for mammals will limit acquisition of arboviruses by this species from infected avian amplification hosts. This feeding preference likely limits the vector potential of Ae. albopictus for North American arboviruses.

Potential West Nile virus (family Flaviviridae, genus Flavivirus, WNV) vectors were assessed during 2003 at indoor and outdoor collection sites in urban Volgograd, Russia, and in three nearby towns and surrounding rural areas. In total, 9,182 female mosquitoes comprising 13 species in six genera were collected. Relative abundance and bloodmeal host utilization differed temporarily and spatially. During June and July in Volgograd, Aedes vexans (Meigen) (85.4%) and Culex p. pipiens L. (7.6%) were the two most abundant species collected indoors, whereas during August, Cx. p. pipiens was the dominant species, accounting for 87.9% of specimens collected. Two WNV-positive mosquito pools were detected in August: one pool was composed of Cx. p. pipiens and the other pool of Culex modestus Ficalbi. Anopheles messeae Falleroni, Aedes caspius (Pallas), Ae. vexans, Cx. modestus, and Cx. p. pipiens used both humans and birds as bloodmeal sources. In urban areas, 20.4% of the Cx. p. pipiens fed on humans, 58.1% fed on chickens, and six specimens were positive for both chicken and human blood. Culex p. pipiens collected from flooded basements were predominantly autogenous (91.7%), whereas adult females resting in buildings with dry basements were composed of 67.5% anautogenous and 32.5% autogenous specimens. Our data suggest that the primary WNV vectors in the Volgograd region were Cx. p. pipiens and Cx. modestus and that intense transmission of WNV to humans in urban areas during the epidemic of 1999 may have been facilitated by the abundance and concentration of anautogenous Cx. p. pipiens in multistory buildings. The role of autogenous Cx. p. pipiens in urban transmission remains unresolved.

Experiments were conducted to determine the effect of a single isometamidium chloride treatment of teneral tsetse flies, Glossina morsitans morsitans Westwood (Diptera: Glossinidae), on the subsequent susceptibility to an infection with Trypanosoma congolense or Trypanosoma brucei brucei. Flies were offered a first bloodmeal on sterile gamma-irradiated defibrinated bovine blood that contained either 10 or 100 μg of isometamidium chloride/ml. Treated flies were subsequently infected with T. congolense IL 1180 or T. b. brucei AnTAR1 on day 3, 5, 10, or 20 posttreatment. To determine the effect of a single treatment with isometamidium chloride at 10 μg/ml on the fly’s susceptibility to infection with isometamidium chloride-resistant trypanosome strains, treated flies were infected with one of two resistant isogenic T. congolense IL 1180 strains 3 d after the first feed. Results showed that a single isometamidium chloride treatment at 10 μg/ml blood sufficed to reduce significantly the fly’s subsequent susceptibility to infection. Only 6.8% of the flies that were treated with isometamidium chloride developed a mature infection with T. congolense in the mouthparts compared with 34.3% of the control group. None of the flies that were administered isometamidium chloride and subsequently infected on day 3 or 6 with T. b. brucei developed a metacyclic infection in the salivary glands compared with 22.7% of the control flies. Likewise for the resistant T. congolense strains, a single treatment with isometamidium chloride significantly reduced the subsequent susceptibility to infection (6.5 and 33.5% of flies with metacyclic infections for treated and untreated flies, respectively). In practice and with respect to the release of sterile male flies to eradicate an isolated tsetse fly population, our results show that administering isometamidium chloride during the first bloodmeal (and before release) would significantly reduce the ability of these released males to transmit trypanosomes.

Intrathoracically inoculated Culicoides sonorensis Wirth & Jones were capable of transmitting vesicular stomatitis New Jersey virus (family Rhabdoviridae, genus Vesiculovirus, VSNJV) during blood feeding on the abdomen of six guinea pigs. None of the guinea pigs infected in this manner developed clinical signs of vesicular stomatitis despite seroconversion for VSNJV. Guinea pigs infected by intradermal inoculations of VSNJV in the abdomen also failed to develop clinical signs of vesicular stomatitis. Three guinea pigs given intradermal inoculations of VSNJV in the foot pad developed lesions typical of vesicular stomatitis. Transmission by the bite of C. sonorensis may have facilitated guinea pig infection with VSNJV because a single infected C. sonorensis caused seroconversion and all guinea pigs infected by insect bite seroconverted compared with 50% of the guinea pigs infected by intradermal inoculation with a higher titer VSNJV inoculum. The role of C. sonorensis in the transmission of VSNJV is discussed.

Entomological investigations by means of dog- and human-baited traps were carried out in summers 2000–2002 in urban and rural areas of the Tuscan region in central Italy. The aim of the study was to define the mosquito species involved in the transmission of Dirofilaria nematodes and to assess the risk that their presence might represent for animal and human health. Nocturnal fieldwork on host-seeking activity and feeding preferences was followed by microscopic identification of the mosquito species attracted and by molecular identification of Dirofilaria parasites in mosquitoes. In total, 3,611 mosquito females belonging to 12 species, largely represented by Culex pipiens L. and Aedes caspius (Pallas), were caught. Some females of each species collected fed on the dogs, indicating their possible role as an intermediate host, but filarial DNA was found only in Cx. pipiens, Anopheles maculipennis s.l. (Meigen), and Coquillettidia richiardii (Ficalbi). In rural environments, the DNA evidence indicated the presence of infective larvae of Dirofilaria immitis, whereas in urban areas, infective larvae of Dirofilaria repens were present. The role of Cx. pipiens as a vector for heartworm disease and subcutaneous infections in natural and artificial environments was confirmed, whereas Ae. caspius seemed refractory to the infection. The different role of the collected species is discussed. The vector competence of An. maculipennis and Cq. richiardii needs further investigation, because the importance of these species poorly represented, and the role of species such as Aedes albopictus (Skuse), characterized by a dominant diurnal activity pattern, has to be evaluated.

Entomological monitoring in four villages situated along an altitude transect in the Hai District of Northeastern Tanzania identified Anopheles arabiensis Patton as the principal vector of malaria and detected seasonal changes in vector behavior. Over a 13-mo sampling period, 10,557 mosquitoes were collected with CDC light traps, pyrethrum spray catches, and pit traps of which 5,969 (56.5%) were An. arabiensis, 762 (7.2%) were Anopheles funestus Giles s.l., 3,578 (33.9%) were culicines, and 248 (2.3%) were nonvector anophelines. Vector densities declined rapidly with increasing altitude, demonstrating a 50% decrease in annual human biting rate for every 86-m rise in altitude. Light traps were found to be more efficient than spray catches for the collection of An. arabiensis. This observation was attributed to increased exophily of this species, most notably in the wet season, and is supported by seasonal changes in the human blood index and fed/gravid ratio. These results indicate that spray catches may underestimate the abundance of exophilic vectors such as An. arabiensis and that entomological monitoring may require more than one collection method, especially at low vector densities. The annual entomological inoculation rate (EIR) decreased sharply with increasing altitude, with large variation around the estimate at low vector densities. Increased transmission because of unpredictable short rains at low altitudes and spatial clustering of infective mosquitoes may contribute to elevated EIR estimates.

From June through September 2003, we conducted a survey of female Aedes triseriatus (Say) for infection with La Crosse encephalitis virus (family Bunyaviridae, genus Orthobunyavirus, LACV) and West Nile virus (family Flaviviridae, genus Flavivirus, WNV) at three locations in Lorain County, Ohio. To determine infection rate and seasonal variation of both viruses in the Ae. triseriatus population, Ae. triseriatus were collected weekly by using gravid traps and CO₂-baited CDC light traps and tested for virus by using reverse transcriptase polymerase chain reaction. In total, 170 pools comprised of 2,143 females were tested for LACV, of which seven were positive; the maximum likelihood estimate of infection rate combined throughout the season was 3.22/1,000. None of 170 pools comprised of 2,158 females tested for WNV were positive. LACV-positive pools were detected between late July and early September.

The first appearances of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) in New Mexico were reported in late summer to early fall 2002. Several dead birds tested positive for WNV, and 78 equine cases were confirmed. All mosquito pools tested (n = 268) were negative. A statewide surveillance program was launched in May 2003 to study the emergence and spread of this new arbovirus in mosquitoes from the Rio Grande valley. Mosquitoes were trapped at 32 sites along a 750-km stretch of the Rio Grande valley. Sites were trapped for one night either weekly or biweekly, by using CO₂-baited CDC light traps and gravid traps. Pools of captured mosquitoes were tested for WNV by reverse transcription-polymerase chain reaction. By mid-July 2003, WNV levels in the mosquito population had reached levels that were detectable by the surveillance program. Positive pools of mosquitoes were found in the Rio Grande valley from mid-July through late September. In total, 75 positive pools were found, from sites throughout the study area. The predominant species infected with WNV in this region were Culex tarsalis (Coquillett) in rural areas, and Culex salinarius (Coquillett) and Culex pipiens quinquefasciatus (Say) in urban areas. There were 202 human cases and 438 equine cases of WNV in New Mexico in 2003, which corresponded well in time with the positive mosquitoes. Our results seemed to be consistent with introduction of WNV in late summer 2002, followed by a period of transmission and amplification cycles between local avian hosts and mosquito vectors.

Passive surveillance for the occurrence of the tick Ixodes scapularis Say (1821) and their infection with the Lyme borreliosis spirochaetes Borrelia burgdorferi s.l. has taken place in Canada since early 1990. Ticks have been submitted from members of the public, veterinarians, and medical practitioners to provincial, federal, and university laboratories for identification, and the data have been collated and B. burgdorferi detected at the National Microbiology Laboratory. The locations of collection of 2,319 submitted I. scapularis were mapped, and we investigated potential risk factors for I. scapularis occurrence (in Québec as a case study) by using regression analysis and spatial statistics. Ticks were submitted from all provinces east of Alberta, most from areas where resident I. scapularis populations are unknown. Most were adult ticks and were collected in spring and autumn. In southern Québec, risk factors for tick occurrence were lower latitude and remote-sensed indices for land cover with woodland. B. burgdorferi infection, identified by conventional and molecular methods, was detected in 12.5% of 1,816 ticks, including 10.1% of the 256 ticks that were collected from humans and tested. Our study suggests that B. burgdorferi-infected I. scapularis can be found over a wide geographic range in Canada, although most may be adventitious ticks carried from endemic areas in the United States and Canada by migrating birds. The risk of Lyme borreliosis in Canada may therefore be mostly low but more geographically widespread than previously suspected.

High incidences of red, itching, and painful welts on people in the midwestern United States led to the discovery of a European species of mite, Pyemotes herfsi (Oudemans) (Acari: Pyemotidae), preying on gall-making midge larvae on oak leaves. The mites’ great reproductive potential, small size, and high capacity for dispersal by wind make them difficult to control or avoid.

Anthropogenic land use changes often alter natural patterns of disease transmission. The goal of this study was to determine whether phosphorus input from sugarcane, Saccharum officinarum L., cultivation in northern Belize could pose a significant environmental impact on malaria transmission by changing vegetation structure and composition of wetlands and associated larval habitats. Our primary focus was on the increased dominance of cattail, Typha domingensis Pers., a favored habitat for Anopheles vestitipennis Dyar & Knab. A land cover classification based on satellite imagery was used to select 20 marshes impacted by agricultural runoff and 20 marshes surrounded by forest (nonimpacted). A 100-m transect was established into each of the 40 marshes. Water, vegetation, and larval sampling were conducted at the 0-, 10-, 25-, 50-, and 100-m locations along the transect. Analyses of larval density data indicated that Anopheles albimanus Wiedemann was negatively correlated with percentage of cover of Typha (R² = 0.39, P < 0.001) but positively correlated with sparse Eleocharis cellulosa Torr. (rush) cover (R² = 0.19, P < 0.05) and presence of cyanobacterial mats (CBM) (R² = 0.33, P < 0.0001). An. vestitipennis was found to be positively correlated with percentage of cover of Typha (R² = 0.19, P < 0.001). Canonical correspondence analysis identified CBM and light as the variables associated with the presence of An. albimanus larvae, Typha cover with An. vestitipennis larvae, and Eleocharis and absence of light with Anopheles crucians (Wiedemann). A positive correlation also existed between marshes adjacent to agricultural activities and presence of An. vestitipennis (R² = 0.37, P < 0.05). These results indicate that marshes in proximity to agricultural fields are conducive for Typha growth, thereby providing habitat for the more efficient malaria vector An. vestitipennis.

Using a threshold model where a minimum level of host viremia is necessary to infect vectors affects our assessment of the relative importance of different host species in the transmission and spread of these pathogens. Other models may be more accurate descriptions of the relationship between host viremia and vector infection. Under the threshold model, the intensity and duration of the viremia above the threshold level is critical in determining the potential numbers of infected mosquitoes. A probabilistic model relating host viremia to the probability distribution of virions in the mosquito bloodmeal shows that the threshold model will underestimate the significance of hosts with low viremias. A probabilistic model that includes avian mortality shows that the maximum number of mosquitoes is infected by feeding on hosts whose viremia peaks just below the lethal level. The relationship between host viremia and vector infection is complex, and there is little experimental information to determine the most accurate model for different arthropod-vector-host systems. Until there is more information, the ability to distinguish the relative importance of different hosts in infecting vectors will remain problematic. Relying on assumptions with little support may result in erroneous conclusions about the importance of different hosts.

Several coastal villages of southern India were affected by the 26 December 2004 tsunami, and 10,749 people were killed. Investigation carried out in the affected villages during fourth, fifth, and sixth weeks posttsunami showed that the fly density was in the range of 12–91.8 flies per sweep net. In total, 3,259 flies belonging to eight species, namely, Musca domestica L., Musca vicina Macquart, Musca sorbens Wiedemann, Calliphora erythrocephala Robineau-Desvody, Sarcophaga ruficornis F., Chrysomyia sp. Robineau-Desvody, Chlorops sp., and Fannia sp. Robineau-Desvody, were recorded. M. domestica was the predominant species constituting 78.2% of the total flies collected. Density of flies was the highest in temporary shelters constructed for the victims, followed by centralized kitchens and devastated human settlements. Lack of waste control at centralized kitchens nearer to the shelters might be the reason for the high fly density in relief shelters. Under these circumstances, outbreak of fly-borne diseases is likely to be aggravated. Therefore, it is suggested that the ongoing space spraying be supplemented with effective waste control measures to reduce the high density of flies.

The insecticidal activity of spinosad was evaluated against susceptible and permethrin-resistant human lice. In a permethrin-susceptible strain of the body louse, Pediculus humanus humanus L. (Anoplura: Pediculidae), the toxicity of spinosad was similar to that established for permethrin, with an LD₅₀ value of 1.2 ng/insect and 2.4 ng/insect, respectively. Topical application of spinosad to populations of permethrin-resistant head louse, Pediculus humanus capitis De Geer (Anoplura: Pediculidae), showed that susceptibility to spinosad was independent of resistance to permethrin. The effectiveness of spinosad against human lice and the low mammalian toxicity reported in the literature suggest that spinosad could be useful for the management of permethrin-resistant human lice.

Despite the successful use of universal primers for amplifying insect mtDNA, specific regions remain difficult to recover and demand the use of taxon-specific primers. In this work, we describe a new set of primers for efficiently amplifying and sequencing the mtDNA control region and three tRNA gene clusters of dipterans of medical and veterinary importance, including Muscidae, Calliphoridae, and Oestridae species. These new primers were useful for investigating the nucleotide information and the structural organization of dipteran mtDNA.

Estimation of allelic frequencies at three microsatellite loci among 20 populations of Glossina morsitans morsitans Westwood, Glossina morsitans submorsitans Newstead, and Glossina morsitans centralis Machado indicated only two of 99 alleles were shared between three subspecies and 18 between any two subspecies; 81 alleles were unshared. The conserved flanking regions of each locus were completely shared. Genetic differentiation among subspecies, based on allele size, was R_ST = 0.87, close to the theoretic maximum value. All evidence suggests longstanding and complete reproductive isolation in nature among the sibling species. They should be elevated to specific rank.

Adult female Tabanus nigrovittatus Macquart (Diptera: Tabanidae) were field collected from a salt marsh in Essex County, Massachusetts. The horse flies were transported back to and tested in the laboratory to determine the effects of octenol (1-octen-3-ol) on engorgement. Flies exposed to octenol strips had a significantly higher engorgement response compared with control flies. To our knowledge, this is the first study to demonstrate an important link between an odor stimulus and the feeding response in Tabanidae. Research examining the link between odor attractants and repellents on the engorgement response is lacking or limited in most hematophagous Diptera. Understanding the role odors have on ingestion is essential to knowing how to interrupt feeding behavior of blood-feeding arthropods, especially for important vectors.