This artcile describes the results obtained from a tick survey conducted in Haller park along the Kenyan coastline. The survey aimed at evaluating tick–host associations, assessing tick population density, and providing baseline information for planning future tick control and management in the park. Ticks (2,968) were collected by handpicking from eight species of wildlife and by dragging in 14 selected sites within the park. A considerable proportion of ticks were also collected from leaves, stems, and bark of most dominant trees, namely, Casuarina equisetifolia L. (Forst. & Forst.), Cocos nucifera L., Adansonia digitata L., Musa paradisiaca L., and Azadiracta indica Adr. Juss. Dragging was conducted in sites predominantly occupied by Cynodon dactylon L. (Pers.), Cenchrus ciliaris L., Stenotaphrum dimidiatum L. (Kuntze.) Brongn., and Brachiaria xantholeuca Hack. Ex Schinz Stapf. and Loudetia kagerensis K. Schum. Hutch. Eight tick species were identified, and the collection included Rhipicephalus pravus Dönitz 1910, Rhipicephalus pulchellus Gerstäcker 1873, Hyalomma marginatum rufipes Koch 1844, Amblyomma gemma Dönitz 1910, Amblyomma hebraeum Koch 1844, Amblyomma sparsum Neumann 1899, Amblyomma nuttalli Dönitz 1909, and Boophilus decoloratus Koch 1844. Given that the identified tick species are known to parasitize humans as well as livestock, there exist risks of emergence of zoonotic infections mediated by tick vectors. In the recreational environment of Haller park, where tick vectors share habitats with hosts, there is a need to develop sustainable and effective tick control and management strategies to minimize economic losses that tick infestation may cause.

Two mosquito species of the subgenus Stegomyia (genus Aedes) (Diptera: Culicidae) on the islands of Palau and Yap (Aedes dybasi Bohart and Aedes maehleri Bohart) are adapted to aquatic habitats occupied by Nepenthes pitcher plants. To reveal the origin of these pitcher plant mosquitoes, we attempted a molecular phylogenetic analysis with 11 Stegomyia species by using sequence data from mitochondrial cytochrome oxidase subunit I and 16SrRNA genes as well as the nuclear 28SrRNA gene. Ae. dybasi, a pitcher plant specialist, was sister to Aedes palauensis Bohart within the scutellaris group from the same islands. Ae. maehleri, an opportunistic pitcher plant mosquito, was in a distinct lineage related to the scutellaris group. The adaptation to pitcher plants could have occurred independently in these two species, and recent differentiation of the pitcher plant mosquito Ae. dybasi from the nonpitcher plant mosquito Ae. palauensis was suggested by a relatively small sequence divergence between these species. We also discuss the implications of this analysis for the phylogeny of some other Stegomyia species.

The female of Argas (Persicargas) keiransi Estrada-Peña, Venzal & González-Acuña (Acari: Argasidae) is described from specimens collected in the type locality in Chile. The female has a unique combination of characters in the dorsal cuticle and in the number and pattern of ventrolateral setae in the basis capituli. Additional features on tarsus I chaetotaxy and dorsal plate are provided for the larva of the species, as observed on flat specimens derived from engorged females collected in the type locality. Keys for the larvae of the New World Persicargas are provided as well as illustrations for prominent characters in hypostome and posterolateral setae. The mitochondrial 16S rDNA sequence of A. keiransi has been obtained, and an analysis of the phylogenetic relationships with other ticks is included. Phylogenetic analysis provides support for a Persicargas grouping of species, separated from species in Argas.

From 1998 to 2003, 4,935 hunter-killed deer in northern and central Illinois were examined for ticks; 4,066 blacklegged ticks, Ixodes scapularis Say, and 6,530 winter ticks, Dermacentor albipictus (Packard) (Acari: Ixodidae), were collected. I. scapularis was the predominant tick species in the northern portion of the study area, with a decreasing north-to-south prevalence gradient. In contrast, D. albipictus was more common in the south with a decreasing south-to-north prevalence gradient. Compared with previous studies, the geographic range for both species expanded into the central portion of the Illinois River. Prevalence and intensity of both tick species were greater on bucks, and infested bucks were geographically more widespread than infested does and fawns. These findings indicate that blacklegged tick and winter tick distributions remain dynamic in the north central United States

Malaria vectors can reach very high densities in villages near irrigated rice fields in Africa, leading to the expectation that malaria should be especially prevalent there. Surprisingly, this is not always the case. In Niono, Mali, villages from nonirrigated areas have higher malaria prevalence than those within the irrigated regions, which suffer from higher mosquito numbers. One hypothesis explaining this observation is that mosquitoes from irrigated fields with high densities are inefficient vectors. This could occur if higher larval densities lead to smaller mosquitoes that suffer elevated mortality. Three predictions of the hypothesis were studied. First, the effect of larval density on larval body size was measured for both Anopheles gambiae Giles and Anopheles funestus Giles. Second, the relationship between larval and adult body size was tested. Third, evidence of an effect of adult size on survivorship in both irrigated and nonirrigated villages during the wet and dry seasons was sought. There was a modest positive relationship between densities of immatures and larval size, and a strong relationship between larval and adult size. Furthermore, adult survivorship was higher in nonirrigated areas. However, there was no effect of size on survivorship between comparable samples from both the irrigated and nonirrigated zones. Although density may have a causal relationship with reduced transmission in the irrigated areas of Niono, it is unlikely to be because higher density leads to smaller body size and lower survivorship.

Rice fields are important sources of mosquitoes in many regions, and rice (Oryza spp.) growing practices can affect mosquito populations. Rice straw incorporation and winter flooding have become common methods to prepare seedbeds, largely replacing burning of straw. These methods increase nutrients during the growing season. We sampled mosquito larvae during 1999–2001 in 16 0.72-ha plots where straw was either burned or incorporated into soil after the previous growing season; these treatments were crossed with either winter flooding or no winter flooding. In 2000, all fields were drained mid-season for an application of herbicide, and then they were reflooded. Mosquitoes responded positively to straw incorporation and winter flooding, especially in combination. The mid-season reflood in year 2 was associated with an order of magnitude increase in Culex tarsalis Coquillett larvae. Results confirm that rice straw and water management can strongly influence mosquito populations.

Knowledge of ecological differences between the molecular forms of Anopheles gambiae Giles (Diptera: Culicidae) might lead to understanding of their unique contribution to disease transmission, to better vector control, and to identification of the forces that have separated them. We compared female fecundity measured as egg batch size in relation to body size between the molecular forms in Mali and contrasted them with their sibling species, Anopheles arabiensis Patton. To determine whether eggs of different egg batches are of similar “quality,” we compared the total protein content of first-stage larvae (L1s), collected <2 h after hatching in deionized water. Egg batch size significantly varied between An. gambiae and An. arabiensis and between the molecular forms of An. gambiae (mean batch size was 186.3, 182.5, and 162.0 eggs in An. arabiensis and the M and the S molecular form of An. gambiae, respectively). After accommodating female body size, however, the difference in batch size was not significant. In the S molecular form, egg protein content was not correlated with egg batch size (r = −0.08, P > 0.7) nor with female body size (r = −0.18, P > 0.4), suggesting that females with more resources invest in more eggs rather than in higher quality eggs. The mean total protein in eggs of the M form (0.407 μg per L1) was 6% higher than that of the S form (0.384 μg per L1), indicating that the M form invests a greater portion of her resources into current (rather than future) reproduction. A greater investment per offspring coupled with larger egg batch size may reflect an adaptation of the M form to low productivity larval sites as independent evidence suggests.

Culicoides fauna was examined at seven feedlots and one rangeland site (Warner) in southern Alberta, Canada, during a 3-yr period. Eight species and species groups accounted for >99% of the Culicoides (Diptera: Ceratopogonidae) captured. The most abundant species or groups were Culicoides gigas Root & Hoffman, Culicoides sonorensis (Wirth & Jones), Culicoides (Selfia) group, and Culicoides palmerae group. These accounted for 78–88% of the Culicoides captured, with the balance being members of the Culicoides cockerellii section, Culicoides crepuscularis Malloch, Culicoides wisconsinensis Jones, and Culicoides yukonensis Hoffman. Univariate and multivariate analyses indicated that the rangeland site was characterized by greater abundance of C. sonorensis and C. palmerae and lower abundance of C. (Selfia) compared with the feedlot sites. The Culicoides fauna was more dissimilar among sites as geographic distance between sites increased. Species of Culicoides captured in this study showed three broad patterns of seasonal abundance. The C. palmerae group had the earliest seasonal activity, with an increase in June, peak in July, and greatly reduced abundance thereafter. C. crepuscularis, C. (Selfia), C. wisconsinensis, and C. gigas had later periods of activity, with peak abundance in July, but moderate abundance in June and August. C. cockerellii, C. yukonensis, and C. sonorensis had the latest periods of activity, with populations increasing through June and July, peaking in August, and declining thereafter. C. sonorensis was somewhat unique on that it was the only species with moderate abundance as late as September.

Aedes triseriatus (Say) (Diptera: Culicidae) females orally infected with La Crosse virus after ingesting an infectious bloodmeal were compared for mating efficiency with females that ingested a noninfectious bloodmeal. After 14-d extrinsic incubation to allow for dissemination of the infection, all females were offered a second noninfectious bloodmeal and were placed in cages with age-matched males for 5 d. After 6 d, insemination rates were determined by detection of sperm in the spermathecae. Insemination rates of the La Crosse virus-infected females were significantly greater than in uninfected females.

Allele frequencies at four microsatellite loci, and morphometric features based on 11 wing landmarks, were compared among three populations of Glossina palpalis gambiensis (Diptera: Glossinidae) in Guinea. One population originated from the Loos islands separated from the capital Conakry by 5 km of sea, and the two others originated from the continental mangrove area close to Dubreka, these two groups being separated by ≈30 km. Microsatellites and wing geometry data both converged to the idea of a separation of the Loos island population from those of the mangrove area. Although occasional contacts cannot be excluded, our results support the hypothesis of the Loos population of tsetse flies being a completely isolated population. This situation will favor a sequenced intervention against human African trypanosomosis and the possibility of an elimination of tsetse from this island.

To facilitate physical genome mapping, we have developed a new cytogenetic photomap for Anopheles stephensi (Liston) (Diptera: Culicidae), an important malaria vector in Asia. The high-resolution images of the ovarian polytene chromosomes have been straightened and divided by numbered divisions and lettered subdivisions. The exact chromosomal locations of eight DNA probes have been determined by fluorescent in situ hybridization. Using the DNA sequences, we have established correspondence between chromosomal arms among An. stephensi, Anopheles gambiae (Patton), and Anopheles funestus (Giles). The results support previous cytogenetic observations of arm translocations taking place during diversification of the species. To make the cytogenetic map useful for population genetics studies, we have indicated the chromosomal positions for the breakpoints of 19 polymorphic inversions.

Before transmission, malaria parasites reside in the salivary glands of their female mosquito hosts. Saliva proteins assist in blood feeding and also may influence the ability of mosquitoes to transmit malaria. We attempted to identify and isolate cDNAs encoding proteins expressed at a high level in the salivary glands of a malaria vector, Anopheles dirus B Peyton & Harrison (=An. cracens) (Diptera: Culicidae). A major protein with an estimated molecular mass of 35 kDa and an isoelectric point (pI) of ≈4 was detected on a two-dimensional (2D) gel. Internal peptide sequences of the protein spot showed high similarity to sequences present in the conserved C-terminal domain of glycine- and glutamate (GE)-rich proteins. A full-length cDNA encoding this protein was isolated from a salivary gland cDNA library of female An. dirus B. The cDNA encoded a 256-residue protein with a calculated molecular mass of 25.4 kDa and a pI of 3.9. BLAST analysis confirmed that it is a member of the GE-rich family. Compositional and sequence analysis of this and other family members revealed a highly acidic N-terminal region of variable length and low sequence conservation and a well conserved C-terminal domain containing 10 identical residues across the 13 known members of the gene family in mosquitoes. The An. dirus B GE-rich transcript was detected by reverse transcription-polymerase chain reaction (PCR) only in the female salivary glands, indicating that this protein is female saliva-specific. The GE-rich proteins may function as a salivary lubricant to facilitate blood feeding.

The biological efficacy as judged by mortality against Anopheles gambiae s.s. of three net samples, one white and two colored, treated with deltamethrin by conventional dipping was compared. Efficacy as well as chemical analysis results showed that uptake of insecticide by white net material was much higher than by colored nets. After a single wash, efficacy of colored nets was reduced significantly below 80% mortality, which is the minimum acceptable level for a field application. This unexpected result could be because of either low uptake of insecticide by colored fibers or high alkalinity on the fibers, resulting from the dyeing process (reduction clearing). α-Cyanopyrethroids, such as deltamethrin, have a low stability in alkaline conditions and rapidly degrade. Practical implications of this finding are of primary importance because the majority of nets currently purchased by institutional buyers for malaria prevention are colored.

Organophosphate/carbamate target resistance has emerged in Culex pipiens L. (Diptera: Culicidae), the vector of Wuchereria bancrofti and West Nile virus (family Flaviviridae, genus Flavivirus) in China. The insensitive acetylcholinesterase was detected in only one of 20 samples collected on a north-to-south transect. According to previous findings, a unique mutation, G119S in the ace-1 gene, explained this high insensitivity. Phylogenetic analysis indicates that the mutation G119S recently detected in China results from an independent mutation event. The G119S mutation thus occurred at least three times independently within the Cx. pipiens complex, once in the temperate (Cx. p. pipiens) and twice in the tropical form (Cx. p. quinquefasciatus). Bioassays performed with a purified G119S strain indicated that this substitution was associated with high levels of resistance to chlorpyrifos, fenitrothion, malathion, and parathion, but low levels of resistance to dichlorvos, trichlorfon, and fenthion. Hence, it is possible that in China, dichlorvos, trichlorfon, and fenthion will still achieve effective control even in the presence of the G119S mutation.

During recent years, long-lasting insecticide-treated nets (LLINs) have been developed to overcome the problems of low retreatment rates, washing, and erratic dose of the insecticide resulting in the dilution of efficacy of the conventional insecticide-treated mosquito nets. These nets are treated at factory level with insecticide either incorporated into or coated around fibers. Olyset net, a polyethylene net with 2% permethrin incorporated within fibers, is one type of LLIN. Therefore, these nets were evaluated for their wash resistance and bioefficacy against malaria vectors Anopheles culicifacies Giles and Anopheles fluviatilis James (Diptera: Culicidae) and other nontarget species. Cone bioassay tests produced 100% mortality in these two vector species with 3-min exposure. Results of the bioassays on washed nets showed 100% mortality in An. fluviatilis even after 20 washings, whereas in An. culicifacies 100% mortality up to 11 washings and 80% mortality up to 20 washings were observed. Cone bioassay tests also were performed on nontarget mosquito species Culex quinquefasciatus Say; house fly, Musca domestica L.; American cockroach, Periplaneta americana (L.); head louse, Pediculus humanus capitis De Geer; and bed bug, Cimex lectularius L. with 30-min exposure. Except for bed bugs, 100% mortality was observed in these nontarget species after 24-h recovery period. In bed bugs, only 25% mortality was observed. The density of An. culicifacies and An. fluviatilis was significantly reduced in houses with Olyset nets compared with those with untreated nets or no nets. Thus, it may be concluded that Olyset nets are highly effective against malaria vectors and moderately against other nontarget household insects.

The repeated use of permethrin and other insecticides for the control of head lice, Pediculus humanus capitis De Geer (Anoplura: Pediculidae), during past decades has resulted in the development of marked levels of resistance. Thus, new alternative insecticides are needed for the control of head lice. We studied the fumigant and repellent properties of essential oils from 16 native and exotic plants in Argentina, and 21 chemical components against permethrin-resistant head lice from Argentina. With a direct vapor-exposure bioassay, the most effective oil was from the native Myrcianthes cisplatensis Cambess (Myrtaceae) with a time to 50% knockdown (KT₅₀) of 1.3 min, followed by exotic species, Eucalyptus cinerea F.V. Muell., Eucalyptus viminalis Labill., and Eucalyptus saligna Smith. with KT₅₀ values of 12.0, 14.9, and 17.4 min, respectively. The most effective components were 1,8-cineole and anisole, with KT₅₀ values of 11.1 and 12.7 min, respectively. Regression analysis of KT₅₀ values and vapor pressures and water-partition coefficients for the essential oil components revealed that the most effective fumigants were among the more volatile components. Repellency assays indicated that the essential oil from Mentha pulegium L. and its benzyl alcohol component were the most effective repellents, having repellency indices of 75.5 and 57.8%, respectively. Thus, some Argentinean plants contain essential oils and components that function as fumigants or as repellents and thereby show potential for development of new control products for head lice.

The horn fly, Haematobia irritans irritans (L.) (Diptera: Muscidae), has become a problem for Brazilian cattle producers even though its introduction into Brazil is relatively recent. Failure to control this cattle pest is becoming a concern, and horn fly populations from several ranches from the state of Mato Grosso do Sul were surveyed for pyrethroid resistance. Susceptibility bioassays revealed that cypermethrin resistance was widespread and reached high levels in horn fly populations throughout the state, with resistance factors (RFs) ranging from 50.4 to 704.8. Synergist bioassays failed to detect a major role for esterases as a pyrethroid resistance mechanism in these populations, except for the highly pyrethroid-resistant Estrela do Oeste population (RF = 704.8). The kdr sodium channel gene mutation was not detected in eight of the 13 populations, but <7% of individuals from four populations and 50% of the flies from Estrela do Oeste exhibited this mutation. Neither the superkdr sodium channel gene mutation nor a resistance-associated gene mutation in the HiαE7 carboxylesterase were found in any of the fly populations. Although target site insensitivity (kdr) and esterase-mediated metabolism occur in horn fly populations from Mato Grosso do Sul state, it seems that they are not the major mechanism causing pyrethroid resistance in most of these populations.

The effects of different pyrethroid insecticides, formulations, and doses on peridomestic populations of Triatoma infestans (Klug) were evaluated in 128 houses with 148 identified infested peridomestic sites in northwestern Argentina between October 2003 and March 2005. Four treatments were randomly assigned within each community: two doses of 5% suspension concentrate β-cypermethrin in water applied with manual compression sprayers, the standard dose (S) at 50 mg and a double dose (2S) at 100 mg active ingredient (AI)/m²; and two emulsifiable concentrates diluted in diesel fuel and applied with power sprayers, 25% cypermethrin (100 mg [AI]/m²) (CF) and 10% permethrin (170 mg [AI]/m²) (DF). Infestation was assessed by timed manual collections with a dislodging agent at baseline, 5, 12, and 17 mo postspraying, and the sites found to be reinfested at 5 mo postspraying were selectively resprayed. Only 2S eliminated T. infestans from all peridomestic sites up to 12 mo postspraying, and it was significantly more effective than all other treatments. At 5 mo postspraying, more sites treated with CF or DF rather than S had bug colonies that probably represented residual foci, which they also failed in eliminating after a second spray. At 17 mo postspraying, the prevalence of reinfested peridomestic sites was 5% for 2S, 29% for S, 43% for CF, and 54% for DF. The application of suspension concentrate pyrethroids in dose twice as large as that currently in use in the attack phase produces a greater initial impact and may eliminate peridomestic populations of T. infestans.

The inflammatory and immune responses seen with the worldwide disease scabies, caused by the mite Sarcoptes scabiei (De Geer) (Acari: Sarcoptidae), are complex. Clinical symptoms are delayed for weeks in patients when they are infested with scabies for the first time. This study was undertaken to elucidate the role of the human dermal microvascular endothelial cell (HMVEC-D) in modulating the inflammatory and immune responses in the skin to S. scabiei. Extracts of S. scabiei were incubated with HMVEC-D and the expression of adhesion molecules and chemokine receptors on the cells and the secretion of selected cytokines were determined by enzyme-linked immunosorbent assay. S. scabiei extract was found to inhibit HMVEC-D expression of E-selectin and vascular cell adhesion molecule-1, although not intercellular adhesion molecule-1. The secretion of interleukin-8 also was inhibited by S. scabiei extract. S. scabiei extract increased expression of the chemokine receptor CXCR-1 and both down-regulated and up-regulated expression of CXCR-2, depending on the concentration tested. These findings help explain the delayed inflammatory reaction to infestation with S. scabiei.

Understanding the dynamics of movement of bacteria within the environment and between species is crucial to unraveling the epidemiology of bacterial diseases and to developing biosecurity measures to prevent dissemination. Many arthropods, some beneficial and some detrimental, inhabit poultry houses. The lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), is a pest commonly found in poultry litter that can harbor pathogens involved in both human and animal health issues. Current farm management practices perpetuate persistent infestations contributing to the dispersal of beetles and pathogens. To study the dissemination of bacteria by this beetle, we require the ability to differentiate internal from external sources of bacteria carried by the beetle. In this study, we tested previously described methods to externally disinfect beetles and found disinfectant efficacies between 40 and 98%. The irregular surface of the insect posed a challenge to cleansing procedures because the surface offered many recesses able to sequester bacteria. Complete bacterial disinfection was achieved with a serial treatment of ethanol and hydrogen peroxide or hydrogen peroxide/peracetic acid.

Intensive small mammal trapping was conducted in 12 counties in New York state during 1998–2000 to investigate the prevalence and site specificity of the Lyme disease spirochete, Borrelia burgdorferi in, and presence of the blacklegged tick, Ixodes scapularis Say on, the wild mice Peromyscus leucopus Rafinesque and Peromyscus maniculatus Wagner and other small mammal species. Previously captured mice (1992–1997) from throughout New York state also were recruited into the study, providing a total of 3,664 Peromyscus from 107 sites in 31 counties. Infection with B. burgdorferi was determined by polymerase chain reaction testing of ear tissue, and rates were determined by species, counties, and regions of the state. B. burgdorferi was detected in 10 small mammal species captured during 1998–2000. Peromyscus captured from Dutchess County in the lower Hudson Valley had the highest infection rate of 21%. The next highest infection rates were in counties within the Capital District: Albany (18%), Rensselaer (17%), and Columbia (13%). From 4,792 small animals examined, we recovered 2,073 ticks representing six species from 414 individuals of 12 mammal species, including 1,839 I. scapularis collected from 315 Peromyscus trapped in five counties. I. scapularis were most often collected from animals trapped in Albany, Rensselear, and Dutchess counties. We used protein electrophoresis of salivary amylase to distinguish between P. leucopus and P. maniculatus species. I. scapularis burdens were 5.7 ticks per P. leucopus and 14.3 ticks per P. maniculatus.

After 35 yr of disease absence, West Nile virus (family Flaviviridae, genus Flavivirus, WNV) circulation has been regularly detected in the Camargue region (southern France) since 2000. WNV was isolated from Culex modestus Ficalbi, which was considered the main vector in southern France after horse outbreaks in the 1960s. Recent WNV transmissions outside of the Cx. modestus distribution suggested the existence of other vectors. To study potential WNV vectors, horse- and bird-baited traps and human landing collections of mosquitoes were carried out weekly from May to October 2004 at two Camargue sites: one site in a wet area and the other site in a dry area, both chosen for their past history of WNV transmission. At the wet site, the most abundant species in bird-baited traps were Culex pipiens L. and Cx. modestus; both species also were found in lower proportions on horses and humans. The most abundant species in horse-baited traps and human landing collections were Aedes caspius (Pallas), Aedes vexans (Meigen), and Anopheles hyrcanus (Pallas) sensu lato; some of these species were occasionally collected with avian blood at the end of the summer. Anopheles maculipennis Meigen sensu lato was an abundant horse feeder, but it was rarely collected landing on human bait and never contained avian blood. At the dry site, Cx. pipiens was the most abundant species in bird- and horse-baited traps. The seasonal and circadian dynamics of these species are analyzed, and their potential in WNV transmission in Camargue discussed.

Hosts of blood-fed anophelines (Diptera: Culicidae) were determined in three riverine villages, 1.5–7.0 km apart, along the Matapí River, Amapá state, Brazil, by enzyme-linked immunosorbent assay midgut analysis for IgG of common vertebrates. Anopheles marajoara Galvão & Damsceno and Anopheles darlingi Root had higher human blood indices (HBI) than Anopheles nuneztovari Gabaldón, Anopheles triannulatus (Neiva & Pinto), and Anopheles intermedius (Chagas), which were relatively zoophilic. HBIs of An. darlingi varied significantly among villages, attributable to a low proportion of human-fed mosquitoes in Santo Antônio. Significantly higher incidence of An. marajoara and An. nuneztovari fed on pig blood at two villages, associated with a low number of pigs in Santo Antônio. The incidences of bovine blood varied significantly among villages for all three of the most common anopheline species. The incidence of mixed meals ranged from 7.1 to 27.6% among common species, and, for An. marajoara, varied significantly among villages. This study demonstrates differences in host selection patterns among villages only a few kilometers apart, which may be influenced by host availability and have important epidemiological consequences.

Preliminary repellent activity of 14 natural products isolated from essential oil components extracted from the heartwood of Alaska yellow cedar, Chamaecyparis nootkatensis (D. Don) Spach., were evaluated against nymphal Ixodes scapularis Say in a laboratory bioassay and compared with technical grade N,N-diethyl-3-methylbenzamide (deet). Four hours after treatment, nootkatone and valencene-13-ol had repellent concentration (RC)₅₀ values of 0.0458 and 0.0712% (wt:vol), respectively; two additional Alaska yellow cedar compounds, nootkatone 1→10 epoxide and carvacrol had reported RC₅₀ values of 0.0858 and 0.112%, respectively. The observed RC₅₀ value for deet was 0.0728% (wt:vol). Although not statistically significantly more active than deet, the ability of these natural products to repel ticks at relatively low concentrations may represent a potential alternative to synthetic commercial repellents.

There is an increasing incidence in the number of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections in the United States. Skin and soft tissue infections caused by MRSA are often perceived as being preceded by a spider bite. Several possibilities exist to explain this phenomenon, including 1) spiders introduce MRSA into the bite wound and thereby serve as a potential vehicle or vector for MRSA; 2) MRSA colonization is an event secondary to the spider bite; and 3) the spider bite is a misguided way for patients or their physicians to explain the initial lesion of their skin or soft tissue infection. We hypothesized that if spiders were able to serve as vehicles or vectors for MRSA infections, they would be colonized with this pathogen. To test this hypothesis, we captured common household spiders and determined the patterns of normal microbial flora isolated from them. Spiders were collected from several homes by their occupants, photographed for identification, and cultured for external and internal microbial flora. Of >100 spiders collected, none was found to carry Staphylococcus aureus or MRSA. Relatively low numbers of microbial flora were isolated, and only a single isolate with pathogenic potential in humans (Aeromonas spp.) was isolated. Common house spiders are unlikely to be a source of MRSA.

The susceptibility of Aedes triseriatus (Say) (Diptera: Culicidae) to low levels of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) was determined and compared with that of Culex pipiens L. to assess the likelihood of its participation in an enzootic cycle involving mammals. Ae. triseriatus and Cx. pipiens were exposed to WNV by feeding on baby chickens with WNV serum titers ranging from 10^{4.1 ± 0.1} to 10^{8.6 ± 0.1} plaque-forming units (PFU)/ml and from 10^{4.1 ± 0.1} to 10^7.0 PFU/ml, respectively. Infection rates and 95% confidence intervals (CIs) of 8% (4, 14) and 25% (15, 38) occurred in Ae. triseriatus and Cx. pipiens after feeding on chickens with WNV titers of 10^{4.1 ± 0.1} PFU/ml and increased to 65% (49, 79) and 100% (72, 100) in Ae. triseriatus and Cx. pipiens after feeding on chickens with titers of 10^{7.1 ± 0.1} PFU/ml. The mean infection rate of Ae. triseriatus ranged from 97% (84, 100) to 100% (79, 100) after feeding on chickens with WNV titers of ≥10^8.2 PFU/ml. The infectious dose (ID)₅₀ values for Ae. triseriatus and Cx. pipiens were 10^{6.5 (6.4, 6.7)} and 10^{4.9 (4.6, 5.1)} PFU/ml, respectively. The combined estimated transmission rate of Ae. triseriatus at 14 and 18 d after feeding on chickens with a mean WNV titer of 10^{8.6 ± 0.1} PFU/ml was 55%. Although Ae. triseriatus is significantly less susceptible to WNV than Cx. pipiens, the susceptibility of Ae. triseriatus to WNV titers <10^5.0 PFU/ml and its ability to transmit WNV suggest that Ae. triseriatus has the potential to be an enzootic vector among mammalian populations.

Anaplasma marginale Theiler is a tick-borne rickettsial pathogen of cattle with a global distribution in both temperate and tropical regions. The pathogen is endemic in regions within the United States, whereas the Canadian cattle population is considered to be free of A. marginale. Farmed bison, Bison bison L., in central Saskatchewan have been found to be infected with A. marginale; however, there is no evidence of transmission from bison to cattle. We tested a Saskatchewan bison isolate of A. marginale (SB1) to determine whether it is transmissible by the Rocky Mountain wood tick, Dermacentor andersoni Stiles. Colonized D. andersoni from the United States and Canada failed to transmit SB1. A separate transmission trial using D. andersoni adults reared from ticks collected in Alberta and British Columbia showed that ticks from these populations could successfully transmit the St. Maries, Idaho, strain of A. marginale. Although the Saskatchewan bison isolate of A. marginale seems not to be transmissible by D. andersoni, in the event of the introduction of a tick-transmissible strain, Canadian D. andersoni are likely to be competent vectors.

Temporal and spatial distribution of egg-laying by Aedes albopictus (Skuse) (Diptera: Culicidae) was investigated in suburban neighborhoods in Raleigh, NC, by using oviposition traps (ovitraps) at fixed sampling stations during the 2002 and 2003 mosquito seasons. Variations in the phenology of oviposition between the two mosquito seasons resulted from differences in the patterns and amounts of rainfall early in the season. Aerial images of each study neighborhood were digitized, and the proportions of specific types of land cover within buffer zones encompassing ovitraps were estimated. Retrospective analyses showed that in some neighborhoods, oviposition intensity was significantly associated with specific types of land cover. However, in general, it seemed that gravid Ae. albopictus searched throughout the landscape for water-filled containers in which to lay eggs. Peridomestic surveys were carried out concurrently with ovitrap collections to estimate production of Ae. albopictus pupae in discarded water-filled containers and the abundance of females in vegetation that made up the resting habitat. Results of linear regression analyses indicated that the mean standing crop of pupae (total and per container) per residence was not a significant predictor of mean egg densities in ovitraps. However, the mean standing crop of adult females was a significant but weak predictor variable, because the magnitude and sign of regression coefficients varied between neighborhoods. Linear spatial regression analyses revealed that oviposition intensity was not spatially dependent on pupal standing crop or the numbers of pupae-positive containers distributed peridomestically. However, a weak spatial dependence on the standing crop of adult females was found in some neighborhoods. Based on spherical variogram models, kriging was carried out to predict the spatial patterns of oviposition in suburban neighborhoods. Focal areas of high and low oviposition intensity were evident in most neighborhoods; however, the spatial patterns of oviposition changed between mosquito seasons. Kriging predictions were evaluated, using cross-validation, by systematically removing each data point from our data set and predicting the removed point by using the remaining points. The root mean square (standardized) error values of best fitting variogram models approximated 1, and plots of standardized PRESS residuals showed no distinct pattern for most neighborhoods, indicating that predictions of the spatial distribution of oviposition intensity were valid. Spherical variogram models are a satisfactory method for describing the spatial distribution of Ae. albopictus oviposition, and kriging can be a useful technique for predicting oviposition intensity at locations that have not been sampled.

The resurgence of visceral leishmaniasis in Brazil increases the need for studies to elucidate the spatial and temporal dynamics of Lutzomyia longipalpis (Lutz & Neiva) (Diptera: Psychodidae), the vector of Leishmania infantum, the causative agent of visceral leishmaniasis in Brazil. Sand flies were captured in peridomestic habitats biweekly for 3 yr. Cross-correlation tests and spectral analysis were used to analyze the simultaneous and lag-time correlations between Lu. longipalpis population densities and abiotic factors of temperature, relative humidity, wind velocity, and rainfall. Distinct seasonal patterns were observed for males and females, with intervals of 6 mo between population peaks for males and 12 mo for females. Peak female population densities lagged 3 mo behind the maximum annual temperature. Female population density was negatively correlated with relative humidity. An increase in average wind velocity was followed by a decrease in the number of females for 2 wk. Understanding the relationship between the seasonal population dynamics of Lu. longipalpis and abiotic factors will contribute to the design of better control measures to decrease transmission of L. infantum and consequently the incidence of leishmaniasis.

The objective of the current study was to investigate the role of waste stabilization ponds (WSP) and wastewater-irrigated sites for the production of mosquitoes of medical importance. Mosquito larvae were collected fortnightly from July 2001 to June 2002 in Faisalabad, Pakistan. In total, 3,132 water samples from WSP and irrigated areas yielded 606,053 Culex larvae of five species. In addition, 107,113 anophelines, representing eight species were collected. Anopheles subpictus (Grassi) and Culex mosquitoes, especially Culex quinquefasciatus (Say) and Culex tritaeniorhynchus (Giles), showed an overwhelming preference for anaerobic ponds, which receive untreated wastewater. Facultative ponds generated lower numbers of both Anopheles and Culex mosquitoes, whereas the last ponds in the series, the maturation ponds, were the least productive for both mosquito genera. An. subpictus and Anopheles stephensi (Liston) were the dominant Anopheles species in wastewater-irrigated sites, with Anopheles culicifacies (Giles) recorded in low numbers. This was also the pattern in nearby sites, irrigated with river water. Among the Culex species, Cx. tritaeniorhynchus was by far the most frequently recorded in both wastewater- and river water-irrigated sites with Cx. quinquefasciatus as the second most abundant species but restricted to wastewater-irrigated areas. Univariate logistic regression analysis showed that presence of An. subpictus and Culex mosquitoes was significantly associated with emergent grass vegetation and low salinity. Regular removal of emergent grass along the margins of the anaerobic ponds and changes in the concrete design of the ponds are likely to reduce the mosquito production, especially of Culex species.

During routine arbovirus surveillance from 2000 to 2004 in New York state (NYS), 14,788 mosquito pools making up 36 species and nine genera were inoculated onto Vero cell cultures to test for a broad spectrum of viruses. Forty-six percent of viruses isolated in cell culture from species, excluding Culex pipiens L. and Culex restuans Theobald, were identified as Bunyamwera serogroup viruses. Here, we report the distribution and level of Bunyamwera activity in NYS detected during this period. We developed specific primers for Cache Valley virus (family Bunyaviridae, genus Orthobunyavirus, CVV) and Potosi virus (family Bunyaviridae, genus Orthobunyavirus, POTV), to facilitate rapid molecular identification of these viruses. Viral RNA was detected in 12 mosquito species by reverse transcription-polymerase chain reaction, with the majority isolated from Aedes trivittatus (Coquillet). We report the first POTV isolation in NYS and describe the development of specific primers to identify both POTV and CVV.

In total, 93,532 female mosquitoes (Diptera: Culicidae) were captured in traps placed in subterranean (catch basin), ground (≈ 1.5 m above ground), and canopy (≈7.0 m above ground) habitats in Stamford and Stratford, CT, during 2003–2005. Culex pipiens L. was the most abundant (64.8%) of the 31 species identified. Significantly greater numbers of Cx. pipiens were captured in canopy-placed mosquito magnet experimental traps, and significantly greater numbers were collected in catch basin-placed (Centers for Disease Control) CDC traps than in CDC traps placed elsewhere. Culex restuans Theobald was captured in significantly greater numbers in traps placed in catch basins. Aedes vexans (Meigen), Aedes cinereus Meigen, and Aedes cantator (Coquillett) were significantly more abundant in ground traps. In total, 429 isolations of West Nile virus (WNV) were made from seven species of mosquitoes from late June through the end of October during 2003 through 2005. Three hundred ninety-eight (92.8%) isolates were from Cx. pipiens. Others were from Cx. restuans (n = 16), Culex salinarius Coquillett (n = 5), Ae. vexans (n = 4), Ae. cantator (n = 3), Aedes triseriatus (Say) (n = 2), and Ae. cinereus (n = 1). Multiple isolates from Cx. pipiens were made each week, primarily during the later part of July through the end of September. Weekly minimum infection rates (MIRs) were lower in 2004 (highest weekly MIR = 7.1) when no human cases were reported in Connecticut in comparison with 2003 and 2005 (highest weekly MIR = 83.9) when human cases were documented. Frequencies of infected pools were significantly higher in Cx. pipiens captured in traps in the canopy and significantly higher in catch basin placed traps than in traps at ground level. The physiological age structure of Cx. pipiens captured in the canopy was significantly different from that of Cx. pipiens collected in catch basins. Invariably, Cx. pipiens captured in the canopy were nulliparous or parous with ovaries in Christophers’ stage 2, whereas 58.7% of the females captured in catch basins possessed ovaries filled with mature oocytes in Christophers’ stage 5. Our results suggest that females in the canopy are seeking hosts, and after digestion of the bloodmeal and development of mature oocytes, they descend to catch basins for shelter and deposition of eggs. WNV was isolated from three, one, and two pools of male Cx. pipiens captured in catch basin-, ground-, and canopy-placed traps, respectively, and from six nulliparous Cx. pipiens females collected in the canopy. Weekly MIR ranged from 1.2 to 31.1 per 1,000 male specimens. These data show that mosquitoes become infected by means other than by blood feeding, possibly by transovarial transmission. The placement of traps in tree canopies and in catch basins can be used to augment current practices of placement of traps near the ground for surveillance of mosquitoes infected with WNV and for studies of the ecology of WNV.

Light traps were used to collect ceratopogonids in East Baton Rouge parish, Louisiana. In total, 46,496 ceratopogonids were sorted from 4,968 light trap collections from 20 November 2002 through 25 November 2004. Two hundred and nine pools containing specimens of 18 species of Culicoides Latreille, seven pools containing specimens of Atrichopogon Kieffer, and five pools containing specimens of Forcipomyia Meigen were tested for West Nile virus (family Flaviviridae, genus Flavivirus, WNV) RNA using real-time reverse transcriptase polymerase chain reaction. Five out of the 209 pools of Culicoides specimens were positive for WNV RNA.

Forensic entomologists rely on laboratory growth data to estimate the time of blow fly colonization on human remains. Several data sets exist for the development of the common blow fly Lucilia sericata (Meigen) (Diptera: Calliphoridae), and although they generally describe similar rates of preadult development, all vary. Such differences could be explained by genetic variation, environmental (rearing) variation, or both. In the study presented here, flies from a single population were reared under variable conditions of food moisture, substrate type, substrate freshness, and sampling, to determine the effect each had on developmental time. Cohorts were tested in a single incubator at a single temperature and humidity, to eliminate effects of undesired environmental variation. Fly developmental times were significantly influenced by multiple laboratory rearing treatments; food moisture, transferring postfeeding larvae to fresh substrate, and destructive sampling affected different stages of development. Developmental times ranged from 329 to 505.5 h, covering the spectrum of variation observed in published data sets. Growth was then compared with larval development on rat carcasses under the same environmental conditions, establishing a link between laboratory-controlled growth and development on carrion. Cohorts raised on rats matured to adulthood between 333 and 337 h, which was best mimicked by the fastest growth treatment observed under laboratory conditions. The large environmental influence on development observed in this study could affect forensic entomology casework and accentuates the need for a standardized means of rearing flies in a laboratory setting that is relevant to decomposition on a corpse.

Potential larval habitats of the mosquito Culex tarsalis (Coquillett), implicated as a primary vector of West Nile virus in Wyoming, were identified using integrated remote sensing and geographic information system (GIS) analyses. The study area is in the Powder River Basin of north central Wyoming, an area that has been undergoing a significant increase in coalbed methane gas extractions since the late 1990s. Large volumes of water are discharged, impounded, and released during the extraction of methane gas, creating aquatic habitats that have the potential to support immature mosquito development. Landsat TM and ETM data were initially classified into spectrally distinct water and vegetation classes, which were in turn used to identify suitable larval habitat sites. This initial habitat classification was refined using knowledge-based GIS techniques requiring spatial data layers for topography, streams, and soils to reduce the potential for overestimation of habitat. Accuracy assessment was carried out using field data and high-resolution aerial photography commensurate with one of the Landsat images. The classifier can identify likely habitat for ponds larger than 0.8 ha (2 acres) with generally satisfactory results (72.1%) with a lower detection limit of ≈0.4 ha (1 acre). Results show a 75% increase in potential larval habitats from 1999 to 2004 in the study area, primarily because of the large increase in small coalbed methane water discharge ponds. These results may facilitate mosquito abatement programs in the Powder River Basin with the potential for application throughout the state and region.

The spatial heterogeneity in the risk of Ross River virus (family Togaviridae, genus Alphavirus, RRV) disease, the most common mosquito-borne disease in Australia, was examined in Redland Shire in southern Queensland, Australia. Disease cases, complaints from residents of intense mosquito biting exposure, and human population data were mapped using a geographic information system. Surface maps of RRV disease age-sex standardized morbidity ratios and mosquito biting complaint morbidity ratios were created. To determine whether there was significant spatial variation in disease and complaint patterns, a spatial scan analysis method was used to test whether the number of cases and complaints was distributed according to underlying population at risk. Several noncontiguous areas in proximity to productive saline water habitats of Aedes vigilax (Skuse), a recognized vector of RRV, had higher than expected numbers of RRV disease cases and complaints. Disease rates in human populations in areas which had high numbers of adult Ae. vigilax in carbon dioxide- and octenol-baited light traps were up to 2.9 times those in areas that rarely had high numbers of mosquitoes. It was estimated that targeted control of adult Ae. vigilax in these high-risk areas could potentially reduce the RRV disease incidence by an average of 13.6%. Spatial correlation was found between RRV disease risk and complaints from residents of mosquito biting. Based on historical patterns of RRV transmission throughout Redland Shire and estimated future human population growth in areas with higher than average RRV disease incidence, it was estimated that RRV incidence rates will increase by 8% between 2001 and 2021. The use of arbitrary administrative areas that ranged in size from 4.6 to 318.3 km²_, has the potential to mask any small scale heterogeneity in disease patterns. With the availability of georeferenced data sets and high-resolution imagery, it is becoming more feasible to undertake spatial analyses at relatively small scales.

The impact of control activities against Triatoma infestans (Klug) (Hemiptera: Reduviidae) in South America has a marked contrast within and outside the Gran Chaco region. Development of a geographic information system, as part of an improvement in control program activities, allowed analysis of the spatial pattern of house infestations by T. infestans before and after house spraying with deltamethrin in the San Martín Department (an arid Chaco region of central Argentina). The overall peridomestic infestation index decreased from 48.2 to 28.2% after insecticide application. House infestation was spatially clustered in regions with low or high infestation levels that were located east and southwest of the department, respectively. This pattern was detected both before and after the insecticide application. Three environmental variables calculated from a temporal series of MODIS imagery (average of night temperature, maximum of day temperature, and temporal variation of vegetation index) were capable of correctly discriminating 96% of the places belonging to either high or low house infestation observed after the insecticide application.

Ecological factors associated with the narrow coastal distribution of Anopheles farauti Laveran s.s. were investigated using decision tree software and a recently developed software tool that permits analysis of environmental gradients across distributional boundaries. Significant variables identified by these procedures were then used to develop ecological niche models that permitted detailed—and improved—predictions of the species’ overall distribution. These methods identified seven climatic factors (four of temperature factors and three atmospheric moisture factors) from among 40 environmental variables related to the range of this species. In addition, the gradient-analysis tool identified elevation as being particularly important. The distributional hypothesis predicted using ecological niche modeling of these factors included all of the record sites from which An. farauti s.s. was collected in northern Australia and successfully reconstructed its narrow limitation to coastal areas. Omission of elevation from analyses resulted in unrealistic predictions of potential distributional areas >100 km inland, where the species has not been found.

We conducted experimental studies to evaluate mosquitoes captured in Paju County, Gyeonggi Province, Republic of Korea, for their ability to transmit West Nile virus (family Flaviviridae, genus Flavivirus, WNV), Japanese encephalitis virus (family Flaviviridae, genus Flavivirus, JEV), and Getah virus (family Togaviridae, genus Alphavirus, GETV) under laboratory conditions. Both Culex pipiens pallens Coquillett and Culex tritaeniorhynchus Giles were highly susceptible to infection with WNV, with infection rates >65% when allowed to feed on chickens with viremias of ≈10⁷ plaque-forming units (PFU) of virus/ml blood. In contrast, Cx. tritaeniorhynchus were significantly more susceptible to JEV or GETV (infection rate 100%) than were the Cx. p. pallens (infection rate 3% for JEV and 0% for GETV) captured in the same area when allowed to feed on chickens with viremias of ≈10⁵ PFU of virus/ml blood. The detection of JEV in field-collected Cx. tritaeniorhynchus in Gyeonggi Province in 2000 and the demonstrated ability of this species to transmit this virus support the importance of the continued vaccination of Koreans against JEV and indicate a risk of infection for nonvaccinated individuals.

An important vector control program is ongoing to lower the risk of malaria transmission in the French military camp of Port-Bouët, Abidjan (Côte d’Ivoire). However, some autochthonous malaria cases are regularly suspected. An entomological survey was conducted in June 2004 in the camp to assess malaria transmission and evaluate the pyrethroid and organophosphate resistance of the malaria vectors. The average mosquito biting rate was 178.0 bites per person per night. Mosquitoes belonging to the Anopheles gambiae (Diptera: Culicidae) complex and the Anopheles funestus group were collected. An. gambiae s.s. molecular form M was the only species of the An. gambiae complex present. The average number of An. gambiae bites was ≈44.3 per person per night. The circumsporozoite index was 0.38% and the entomological inoculation rate estimated to be 1.2 infective bites per week for the study period. The kdr and ace1 gene frequencies in the An. gambiae population were 0.70 and 0.15, respectively. Personnel living in the French barracks of Port-Bouët are thus at high risk of being bitten by parasite-infected mosquitoes. Such an entomological inoculation rate, usually found in African peri-urban environments, was unexpected considering the extensive effort deployed to control mosquitoes in the camp. Insecticide resistance could explain the inefficacy of the vector control program but the spraying strategy is also questionable.

To evaluate the host-feeding patterns of Aedes vexans (Meigen) and Culiseta melanura (Coquillett) as secondary vectors of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) in Northeastern United States, we identified the source of vertebrate bloodmeals by sequencing portions of the cytochrome b gene of mitochondrial DNA. Analysis of polymerase chain reaction products from a total of 119 Ae. vexans revealed that 92.4% of individuals acquired blood solely from mammalian and 2.5% from avian hosts. Mixed bloodmeals from both avian and mammalian hosts were detected in 5% of individuals of this species. Ae. vexans obtained vertebrate bloodmeals most frequently from white-tailed deer (80%) followed by domestic horse, American robin, eastern cottontail, and domestic cat. In contrast, Cs. melanura fed predominantly on avian species (89.6%) but exhibited some inclination for mammalian blood (4.2%). Individual mosquitoes containing mixed bloodmeals were also identified in 6% of Cs. melanura. American robin was the most common source of vertebrate blood for Cs. melanura (23%), followed by wood thrush and gray catbird. American crow represented only 2% of the bloodmeals identified in Cs. melanura, as was similarly found with other recognized Culex vectors of WNV in the northeast. These findings support the view that Ae. vexans is likely to be a relatively important “bridge vector” to large mammals, including deer and horse, whereas Cs. melanura likely plays a secondary role in enzootic transmission of WNV among free-ranging birds in more rural environs.

Pachycondyla chinensis (Emery) (Formicidae: Ponerinae), a species introduced into North America >70 yr ago, is found throughout Southeast Asia. Stinging of zookeepers by P. chinensis at the Greenville Zoo (Greenville, SC) initiated an investigation of this exotic species and a survey of sting victims. Eighty percent of sting victims experienced local reactions, including swelling <5 cm in diameter around the sting site, recurring pain, skin redness, and mild-to-severe urticaria. These symptoms lasted 2 h to 5 d. Twelve percent of the sting victims reported minor reactions, including no swelling, localized redness, minor pain sensation at the time of sting, mild urticaria, and symptoms lasting <1 h. Eight percent of the sting victims reported significant local reactions, including swelling >5 cm in diameter around the sting site, recurring pain, skin redness, severe urticaria, and symptoms lasting 3–14 d. P. chinensis represents an emerging public health threat throughout its present range in the southeastern United States (i.e., Georgia, North Carolina, South Carolina, and Virginia). Because of reported adverse reactions to stings of P. chinensis, further studies on its ecology and medical and veterinary importance need to be undertaken.

Adults and nymphs of Amblyomma exornatum Koch (Acari: Ixodidae), an exotic African tick of monitor lizards, were collected from a Gray’s monitor lizard, Varanus olivaceus Hallowell, that died in a reptile facility in Alabama. Nine adult ticks were tested by polymerase chain reaction for rickettsial agents. DNA from a novel spotted fever group Rickettsia was amplified and sequenced from one of the nine ticks. The novel Rickettsia was most similar to “Rickettsia anan,” which is associated with Amblyomma from Asia. The detection of a spotted fever group Rickettsia in exotic ticks emphasizes the potential threat posed by the importation and propagation of exotic animals in the United States.