In addition to their importance to human and animal health, vector-borne diseases are fascinating systems to study. The involvement of multiple species whose biologies and life cycles cover differing space and time scales makes it extremely difficult to predict epidemics. A single environmental factor may have opposite impacts on the system at different points in time. Patchiness at different geographical scales may have very different causes, so it is important to identify the proper scale for a particular study. New developments in remote sensing, GIS, and spatial analysis make it easier to tease out causes of observed patchiness. Interdisciplinary collaboration is essential for many of the projects we carry out, but this requires awareness of the differences between disciplines and the ability to effectively communicate with each other. It is only by forming multi-disciplinary groups to focus on specific vector-host-pathogen systems that we will be able to answer the most interesting (and pressing) problems in our field.

We adapted the Seliwanoff method to quantify fructose in mosquitoes. This method showed a minimum detection limit of 2.4 μg of fructose, and was more reliable and nearly four times more sensitive than the anthrone test. The Seliwanoff method was used to measure the maximum sugar intake by individual mosquitoes and to determine the digestion time of this nutrient by both Aedes aegypti and Aedes albopictus in the laboratory. Sugar intake by Ae. albopictus was up to 1.7 times higher than that of Ae. aegypti. The amount of sugar ingested by females was up to 2.5 times higher than that of males in both species. After 48 h, a fructose meal was not detected any longer in either species. The Seliwanoff method was applied to measure fructose content of field-collected Ae. aegypti males and females in Rio de Janeiro. Results showed that even Ae. aegypti females do feed on sugars. The standardized Seliwanoff method proved to be reliable for measuring the sugar content of individual mosquitoes and can be used wherever estimation of small quantities of fructose is needed.

The discovery of an unusual specimen of Psorophora in Mississippi led to a search for new diagnostic characters on the seven United States species of Psorophora (Janthinosoma): Psorophora cyanescens, Ps. ferox, Ps. horrida, Ps. johnstonii, Ps. longipalpus, Ps. mathesoni, and Ps. mexicana. New characters were found and diagnostic descriptions and a new key are provided for identifying female specimens. The new key stresses morphological differences other than color patterns on the hindtarsi, however, notes on hindtarsal color and other variations found on each species are also provided. The status of Ps. mexicana specimens recorded from Texas is reviewed and a list of collections of this species since the 1945 record in Texas is provided. Evidence is provided supporting the recognition of Ps. mexicana as a distinct species.

The success of an invasive species becoming established in a new region often depends on its interactions with ecologically similar resident species. The propensity of the newly-established mosquito Aedes japonicus to inhabit rock pools throughout the eastern United States provides a natural setting for interspecific larval competition with the native Aedes atropalpus. A laboratory experiment conducted in simulated rock pools to evaluate larval interactions between and within these two species suggested that the performance of both species was more significantly impacted by intraspecific conditions than interspecific conditions of the same mosquito density. Aedes atropalpus was apparently more sensitive to larval densities than Ae. japonicus because it reproduces autogenously, requiring a lengthened period of larval development to obtain nutrient reserves for egg development, which may ultimately put Ae. atropalpus at a disadvantage under larval conditions of competition and limited resources. Excessively stressful experimental conditions, as evidenced by reduced body size, and thus fecundity and estimated finite rate of increase, may have obscured the effects of larval competition between these species. The impact of larval competition between these species in rock pool communities warrants further investigation under more ecologically realistic experimental conditions.

Male stable flies require at least one or more blood meals to reach sexual maturity and are often caught in CO₂- baited traps. We tested the hypothesis that young male stable flies (one to three days, one blood feeding session) would be more responsive to CO₂ bait than older male stable flies by monitoring the upwind movement of different-aged male stable flies exposed to CO₂ using a wind tunnel. The proportion of males moving upwind toward CO₂ decreased with age (days), from 49% for males <= 3 days old, to 4.5% for males > 3 days old. To further test this, we conducted daily sampling of stable fly populations at a beef farm using a CO₂-baited cloth trap. We found that days on which a high proportion of males were caught, females were predominantly from early developmental stages, indicating that proportionately more males were caught from field populations made up of younger cohorts. These results were consistent with the wind tunnel experiment patterns.

Although insecticides play a crucial role in malaria control programs, this strategy is threatened by the development of resistance in the vectors to commonly used public health insecticides. Due to their known efficacy and lower toxicity to humans and non-target organisms, pyrethroids have been used in many vector control projects. In West Africa, pyrethroid resistance in the major malaria vector, Anopheles gambiae, had been reported in several countries. It was, therefore, imperative to investigate the susceptibility of this very important malaria vector in Ghana and characterize the resistance mechanism. Larvae of Anopheles gambiae sensu lato were collected from rural and urban sites and reared to adults. Species identification was by morphological characteristics, PCR, and HhaI restriction digest. Female mosquitoes that were two to three days old were selected and exposed to World Health Organization (WHO) diagnostic doses of three pyrethroids. A susceptible laboratory strain of An. gambiae sensu stricto was used as a reference. Both survivors and dead mosquitoes from bioassays were screened for the knockdown resistance mutation. An. gambiae sensu stricto was the only sibling species of the complex present in these localities with the molecular S form being predominant (>95%). Resistance to pyrethroids up to 8.5 fold was observed, with very high kdr frequency. The relative ease in using molecular techniques has resulted in rapid detection of ostensible insecticide resistance genes in malaria vectors. However, it is even more important to complement these molecular tools with routine insecticide testing in the field, especially if the insecticides are earmarked for public health use.

The removal of large herbivorous mammals can cause dramatic increases in the densities of small mammals. These small mammals are hosts for a variety of ectoparasites, many of which are important pathogens of human diseases such as plague and murine typhus. It is thus valuable from a human health perspective to understand if large herbivore removals can indirectly affect ectoparasite numbers and thus potentially alter disease risk. To make this determination, we experimentally excluded large herbivores and measured the number of fleas present on the numerically dominant small mammal, the pouched mouse, Saccostomus mearnsi. Removing large herbivores nearly doubled S. mearnsi density, while the percentage of mice infested with fleas (prevalence) and the average number of fleas per sampled mouse (intensity) remained constant. The net effect of doubling the number of mice via the removal of large herbivores was a near doubling in the number of fleas present in the study habitat. Because these fleas also parasitize humans and can serve as disease vectors, this work empirically demonstrates a potential mechanism by which ecosystem alterations could affect human risk for zoonotic diseases.

Mosquito faunal studies were carried out in five separate wetland regions in the Czech Republic during 2004–2007, sampling with dry ice-baited and sentinel host-baited CDC traps. A total of 79,245 adults was identified, representing 23 mosquito species that belonged to the genera Anopheles, Culiseta, Coquillettidia, Aedes, and Culex. Our findings reveal that the mosquito fauna is enriched by new elements in the Mediterranean region. Historical and CDC trap data suggest that the newly-emerging potential malaria vector, Anopheles hyrcanus, has reached the northern limit of its distribution in the Czech Republic, and the important West Nile virus (WNV) vector, Culex modestus, has widened its distribution in the Czech Republic. No significant differences were observed in a total number of mosquitoes collected by traps baited with either the sentinel animals or with CO₂, although species abundance differed. A relatively higher proportion of Cx. modestus was collected in the sentinel-baited traps, while the proportion of Cx. pipiens was higher in the CO₂-baited traps.

A study was designed to test the insect development inhibitors fluazuron and lufenuron for the control of fleas on sylvatic rodents as an adjunct to the control of plague. Historical data of flea burden from 15 prior years of study at Chuchupate Campground, Ventura County, CA, were compared to six years of treatment period data to determine if fluazuron and lufenuron were effective in controlling flea densities. The insect development inhibitors, delivered systemically via a feed cube, reduced flea loads effectively on California ground squirrels (Spermophilus beecheyi), long-eared woodrats (Neotoma macrotis), and mice (Peromyscus spp.) but not on Merriam's chipmunks (Tamias merriami).

Biting patterns of natural populations of Anopheles minimus s.l. females entering experimental huts treated with DDT and deltamethrin were carried out at Pu Teuy Village, Sai Yok District, Kanchanaburi Province, western Thailand. Two experimental huts, control and treatment, were constructed in the fashion of local Thai homes. Pre-spray biting activity of An. minimus females peaked at 19:00–22:00. Post-treatment exposure continued to show greater landing activity during the first half of the evening. An overall greater proportion of An. minimus females entered the hut treated with deltamethrin compared to DDT. The hut fitted with DDT-treated net panels showed a 71.5% decline in attempted blood feeding, whereas exposure to deltamethrin-treated panels resulted in a 42.8% human-landing reduction. DDT exhibited significantly more pronounced (P < 0.05) effects in overall reduction of biting activity than did deltamethrin.

Serosurveys conducted where West Nile Virus (WNV) caused health impacts were used to construct a model of potential worst case health impacts in a suburban setting. This model addressed two common public perceptions regarding mosquito control activities and WNV disease: it is not a disease of major consequence, and exposed populations quickly become immune. Comparisons to blood bank infection and serious disease incidence data were similar to some of the serosurvey model results. Accounting for theoretical increasing immunity, even over a 20-year period, did not substantially reduce the potential impacts. The model results were approximately an order of magnitude greater than those actually experienced in Suffolk County, NY; differences in mosquito populations and/or the degree of mosquito control between Suffolk County and serosurvey sites seem to be the reason for the differences.

We compared the behavioral responses of Aedes aegypti females to essential oils extracted from native plants Melaleuca leucadendron (ML), Litsea cubeba (LC), and Litsea salicifolia (LS) by using an excito-repellency test chamber. Mortality of Ae. aegypti females following 24 h holding period post-contact and non-contact trials were observed. No mortality was seen in escaped mosquitoes after direct contact with essential oils ML and LS, and low mortality (2.3–20.4%) with LC. Likewise, in all non-contact trials, no mortality was observed in escaped females from all three treatments, whereas low mortality was seen in non-escaped mosquitoes exposed to LC (0–14.3%) and LS (0–17.1%). Ae. aegypti showed significantly higher escape rates from contact chambers treated with ML and LC compared to LS, regardless of test concentrations (P<0.05). Non-contact repellent responses were significantly pronounced with LS, except at the highest (6.0%) concentration. We conclude that essential oils from all three botanicals exhibit significant irritant and repellent properties against Ae. aegypti and deserve further investigation for possible use as active ingredients in topical (skin) and indoor dispersed repellent systems.

Ten different mosquito species representing five genera were allowed to feed on human blood containing microfilariae (5.5–6.5 mf/μl) of nocturnal subperiodic Wuchereria bancrofti from Kanchanaburi Province, Thailand. Aedes aegypti, Aedes albopictus, Aedes desmotes, Downsiomyia species (=Finlaya Niveus Group), Culex quinquefasciatus, Anopheles dirus A, An. maculatus, An. minimus, Armigeres subalbatus, and Mansonia uniformis were fed under laboratory conditions using an artificial membrane feeding procedure. All species had adequate feeding responses (68–87.3%) and survival (66.4–81.3%) 12–15 days post-feeding. Anopheles maculatus was the most susceptible (73.1%) for development of infective thirdstage larvae (L3), followed by An. minimus (61.0%), Downsiomyia species (27.3%), Ae. desmotes (24.2%), An. dirus A (24.7%), Cx. quinquefasciatus (19.2%), Ma. uniformis (9.2%), and Ae. albopictus (0.01%). Aedes aegypti and Ar. subalbatus were found to be completely refractory. An. maculatus produced the greatest mean number of L3 per infective mosquito (5.6 L3) and Ae. albopictus the least (1 L3). The two Anopheles demonstrated significantly greater susceptibility (P < 0.05%) to W. bancrofti than the two Aedes species regarded as natural vectors.

Understanding oviposition behavior is important to behavioral and vector ecologists because of its potential use in developing vector control strategies for insect-borne infectious diseases. Our study compared the oviposition behaviors of Anopheles gambiae s.s mosquitoes from two different regions of East Africa, Mbita Point, Kenya and Ifakara, Tanzania. The work sought behavioral evidence for the presence of an olfactory cue that modulates oviposition behavior in these different regional strains of Anopheles gambiae s.s. Results demonstrated that the larval rearing water of the different mosquito strains produced a signal that yielded a positive oviposition response from Anopheles gambiae s.s. gravid females of the same region. This not only implies the presence of an olfactory determinant of oviposition but it also could be a model for how speciation could arise within related taxa of mosquitoes.

When white-tailed deer, Odocoileus virginianus, feed on corn bait dispensed by 4-poster tick control devices, they rub against paint rollers impregnated with acaricide. Gray squirrels, Sciurus carolinensis, also feed on the corn bait in the feeding troughs of 4-posters, but in doing so, leave abundant corn fragments and meal that impede the flow of uneaten corn into the troughs. Large accumulations of fragments and meal adversely affect the operation of 4-posters and their use by deer. A battery-operated closure mechanism controlled by a photo sensor was developed to block the flow of corn into the troughs during the day when squirrels are active and deer infrequently visit 4-posters. The effectiveness of the diurnal corn restriction (DCR) concept and restriction mechanism was tested in a field trial at a tick-infested site in Maryland. DCR effectively eliminated accumulation of whole corn, partially eaten corn and corn meal in corn troughs associated with squirrel feeding. At the same time, deer usage of 4-posters was not diminished.

Dengue in Cambodia is mainly transmitted by Aedes aegypti (L.) mosquitoes that primarily breed in large, concrete jars (≥200 liters) used for the storage of water for domestic use. Following a preliminary risk assessment, long-lasting insecticidal netting (LN) treated with deltamethrin was incorporated into the design of the covers for these jars. Their effect on immature and adult female populations of Ae. aegypti in six villages in a peri-urban area of Cambodia were compared with populations in six nearby control villages before and for 22 weeks after distribution of the jar covers. There were significantly fewer pupae per house in intervention villages than in control villages (6.6 and 31.9, respectively, p<0.01). Fewer pupae were recovered from intervention houses than from control houses at every post-intervention assessment. Two weeks after the intervention, the average number of indoor resting female Ae. aegypti per house in the intervention villages had declined approximately three-fold, whereas in the controls there was only a slight reduction (16%). The magnitude of the difference between the two areas diminished over time, which contact bioassays confirmed was likely due to a gradual reduction of insecticidal effect of the jar covers. In the study area, insecticide-treated covers for large concrete water storage jars were efficacious for controlling Ae. aegypti in the protected water jars and with a demonstrable effect on adult densities and survival. Further studies of this targeted container strategy in Cambodia, and elsewhere, are recommended. However, improvements in technology that would extend the duration of insecticidal effectiveness of LN materials may be needed for the development of cost-effective public health applications.

West Nile virus (WNV) arrived in North America and spread rapidly through the western hemisphere. We present a series of tests to determine whether ecological factors are consistently associated with WNV transmission to humans. We analyzed human WNV cases in the states of Illinois, Indiana, and Ohio in 2002 and 2003, building ecological niche models to associate WNV case occurrences with ecological and environmental parameters. In essentially all tests, both within states, among states, between years, and across the region, we found high predictivity of WNV case distributions, suggesting that one or more elements in the WNV transmission cycle has a strong ecological determination. Areas in the geographic region included in this study predicted as suitable for WNV transmission tended to have lower values of the vegetation indices in the summer months, pointing to consistent ecological differences between suitable and unsuitable areas.

Rodent-borne bartonellae have been identified as human pathogens. Little is known about Bartonella infections in woodrat hosts and their fleas and how woodrat-flea associations may affect the dynamics of Bartonella infections. We collected blood samples and fleas from two species of woodrats (Neotoma micropus and N. albigula) from Santa Fe County, NM, from 2002–2005. The most predominant flea species were Orchopeas sexdentatus and O. neotomae. Bartonella prevalence in woodrats was 64% overall, with a lower prevalence occurring in the pre-reproductive period compared to the early and late reproductive periods. A negative correlation between Bartonella prevalence in N. micropus and weight of N. micropus was observed. Flea load in Neotoma species was highest in the early reproductive period compared to the pre- and late reproductive periods and was higher in N. micropus compared to N. albigula. Bartonella prevalence in fleas was highest in the early reproductive period and lowest in the late reproductive period, and it was higher in fleas collected from N. micropus than in fleas collected from N. albigula. Abundance of O. sexdentatus was significantly higher in N. micropus compared to N. albigula, and abundance of O. sexdentatus and O. neotomae was highest in the early reproductive period. No direct correlations were found either between Bartonella prevalence in woodrats and in fleas or between Bartonella prevalence in woodrats and flea loads. Out of 25 partially characterized Bartonella isolates from Neotoma woodrats, 24 belonged to one genogroup based on sequencing of the gltA gene.

The horse fly (Diptera: Tabanidae) fauna of Bosnia and Herzegovina consists of 62 species belonging to ten genera. The present study adds eight new records for the fauna of Bosnia and Herzegovina. These new records are Chrysops flavipes Meigen, Hybomitra tropica (Linnaeus), Tabanus darimonti Leclercq, Tabanus eggeri Schiner, Tabanus miki Brauer in Brauer and Bergenstamm, Tabanus shannonellus Kröber, Haematopota bigoti Gobert, and Haematopota subcylindrica Pandellé. Most of the species belong to the Boreal-Eurasian group (28), followed by the Mediterranean group with 17 species, the South European group with 13 species, the Afro-Eurasian arid group and the European group with two species each. This paper presents the first comprehensive collection data on the horse fly fauna of this part of the Balkan Peninsula.

Throughout Korea, small mammals are hosts to a number of disease-causing agents that pose a health threat to U.S. and Korean military forces while they conduct field-training exercises. A seasonal rodent-borne disease surveillance program was established at two firing points (FP), FP-10, and FP-60, and conducted over five years from 2001 through 2005 in response to hantavirus cases among U.S. soldiers. The ecology of these sites consisted primarily of tall grasses associated with semi-permanent and temporary water sources (drainage ditches and a small stream) and dry-land agriculture farming. Eight species of rodents and one species of insectivore were collected, including Apodemus agrarius, Micromys minutus, Mus musculus, Rattus norvegicus, Tscherskia triton, Microtus fortis, Myodes regulus, and Crocidura lasiura. The striped field mouse, A. agrarius, (primary reservoir for Hantaan virus, the causative agent of Korean hemorrhagic fever), was the most frequently collected, representing 90.6% of the 1,288 small mammals captured at both sites. Reported herein are the ecological parameters, seasonal population densities, and seasonal population characteristics associated with small mammals collected at two military training sites in the Republic of Korea.