During long-term ecological studies carried out between 1990 and 2000, a total of 67 mosquito species were collected from Gorakhpur District, Uttar Pradesh, India, of which 43 were documented for the 1st time. The genus Aedes was represented by 15 species, Anopheles by 15, Culex by 24, Mansonia by 3, and Mimomyia, Ochlerotatus, and Verrallina by 2 each. The genera Aedeomyia, Armigeres, Coquillettidia, and Uranotaenia were represented by single species. The impact of ecological changes on mosquito fauna in Gorakhpur District is discussed. The role of culicine mosquitoes in disease transmission in the area is highlighted.

In the Anopheles minimus complex, 2 sibling species (A and C) are generally accepted. Recently, a 3rd species, provisionally designated An. minimus species E, has been described from the Ryukyu Archipelago, Japan, based on crossing experiments (A and E), DNA analysis, mitotic karyotypes, and some morphological characteristics. The present study reports the results of crossing experiments between species C and putative species E. Hybridization between the progeny of An. minimus species C from Thailand and putative species E from Japan revealed postzygotic genetic incompatibility. Although F₁ hybrid progeny were obtained from both directions of crosses, the hybrid males from C female × E male crosses were completely sterile, with atrophied testes and accessory glands. In addition, the external terminalia of all of these males never completely rotated and the males failed to copulate by artificial mating. In E female × C male crosses, the hybrid males showed partially sterile testes in which most spermatozoa were abnormal (enlarged head) and inactive, and they had very little success in inseminating females. The salivary gland polytene chromosomes of F₁ hybrid larvae from species C female × species E male showed a fixed heterozygous inversion on the 3L arm. Those hybrids F₁ from species E female × species C male showed partial asynapsis on identified arms (2R and 3L) and a fixed heterozygous inversion on the 3R arm. When the hybrid females from both directions of crosses were F₁ backcrossed with either C or E males, they produced male progeny with abnormal spermatozoa. Study of mating behavior in a 30 × 30 × 30-cm cage showed that the C males failed to mate with either C or E females, indicating that species C males cannot breed in confined spaces (lack stenogamy). Putative species E males had little success in inseminating species C females. This study provides strong evidence of genetic incompatibility between An. minimus species C and putative species E, supporting previous data that species E is a distinct species in the An. minimus complex.

Enhanced mosquito surveillance in Mississippi has confirmed the presence of Mansonia titillans and Ochlerotatus trivittatus, which represent new state records for Mississippi. Recent records of Aedes albopictus, Anopheles maverlius, An. quadrimaculatus, An. smaragdinus, and Ochlerotatus hendersoni, and questionable records of Ochlerotatus dorsalis, Oc. stimulans, and Psorophora pygmaea are reviewed.

Aedes aegypti (L.) density indices obtained in a dengue fever (DF) endemic area were compared. One hundred and twenty premises, in an urban area of Colombia where dengue type-1 and type-2 virus cocirculated, were randomly selected and sampled for 7 months. The geometric mean monthly numbers (density index, DI) of Ae. aegypti eggs (ODI), 4th instar larvae (LDI), pupae (PDI), and adults (ADI) were calculated based on the use of ovitraps, nets, and manual aspirators, respectively. A negative temporal correlation was observed between the LDI and the ODI (r = −0.83, df = 5, and P < 0.01). Positive temporal correlations were only observed between the LDI and the PDI (r = 0.90, df = 5, and P < 00.5) and the Breteau and House indices (r = 0.86, df = 5, and P < 0.01). No other correlations were found between these indices and any of the other density indices or the incidence of suspected DF cases in residents, the temperature, the rainfall, or seasonal fluctuations. Our results were, therefore, probably due to the most productive Ae. aegypti breeding sites (large water containers) being located indoors within this study area. The number of adult female Ae. aegypti/ person (n = 0.5) and pupae/person (n = 11) in our study area were lower and dramatically higher than the transmission thresholds previously reported for adult and pupae, respectively. Because there were confirmed DF cases during the study period, the transmission threshold based on the Ae. aegypti pupae was clearly more reliable. We found that the mean ovitrap premise index (OPI) was 98.2% during this study and that the mean larval (L-4th instars) premise index (LPI) was 59.2%, and therefore we suggest that the OPI and LPI would be more sensitive methods to gauge the effectiveness of A. aegypti control programs.

Inundation of dried emergent vegetation that has been knocked down using heavy equipment is a vegetation management strategy that provides an inexpensive source of supplemental organic carbon to stimulate denitrification, a process important for nitrate removal in constructed treatment wetlands. The abundance of larval mosquitoes (Culex sp. and Culiseta sp.) in multipurpose constructed wetlands that had undergone autumnal vegetation management intended primarily to enhance denitrifying bacteria was significantly higher than in wetlands that remained in continuous operation. Mosquito abundance in wetlands that had undergone vegetation management during autumn was much lower than that observed during spring in a previous study; nevertheless, vegetation management practices that inundate dried, felled macrophytes are contraindicated for mosquito control.

The main objective of the present work was to establish and maintain a colony of Ochlerotatus taeniorhynchus, Riohacha strain, under laboratory conditions and to study its life cycle. The colony's insectary was established from adult male and female mosquitoes collected from peripheral neighborhoods of Riohacha, Colombia. Environmental conditions established in the insectary were 26.5°C average temperature, 80% average relative humidity, and 12 h photoperiodicity. Eight continuous generations were taken into account for maintaining the mosquitoes and analyzing their life cycle. The male mosquito's average life cycle was 26.8 days. The female's cycle was 30.8 days. Analysis of each of the biological stages of development (mean days) produced the following results: egg incubation 4.55 ± 0.291, larvae 8.28 ± 0.499, pupae 1.32 ± 0.215, adult male 12.65 ± 5.920, and adult female 16.73 ± 6.034. The Riohacha colony has been maintained for 32 generations in 31 months. Comparison of the Riohacha colony with the previously established Cartagena and Barranquilla colonies showed few differences in the duration of stages of the life cycle between strains.

St. Tammany Parish, Louisiana, experienced an outbreak of West Nile virus (WNV) in 2002, with 40 human cases and 4 deaths, most occurring from June to August. Culex pipiens quinquefasciatus was believed to be the primary vector of WNV during the outbreak, although circumstantial evidence suggests that Aedes albopictus also may have been involved in transmission. Dead bird reports were the 1st indication of the outbreak and were an excellent indicator of WNV activity; however, sentinel chickens were the most effective in tracking viral activity. Although sentinel chickens tested positive 2–3 wk after the 1st dead bird, they peaked at about the same time as human cases, and continued testing positive when viral activity was no longer detected in birds and mosquito pools. Lag time between the 1st positive sentinel chicken and the peak in human cases was 6 wk. If this trend continues in the future, sentinel chickens could be used to predict the peak in number of human cases. The 2002 WNV outbreak had a strong impact on operational budget of the St. Tammany Parish Mosquito Abatement District (88% increase above the 3-year average). Vector control activities accounted for most of the operational increase and consisted of targeted population reduction of known WNV-competent mosquito species. The goal of these activities was to prevent new human WNV cases. The 3- to 10-fold reduction in vector mosquito populations from May to August, together with a dramatic drop in number of new human cases by the end of August, indicated that our strategy was effective.

Sentinel chickens are used to detect western equine encephalomyelitis, St. Louis encephalitis, and West Nile virus activity. Flocks that receive high mosquito exposure will be most effective for surveillance purposes. However, mosquito population indices at the flock sites may only provide an indirect measure of potential exposure. Therefore, we developed an indirect enzyme immunoassay to detect chicken antibodies to salivary gland antigens (SGAs) from Culex tarsalis, the primary arbovirus vector in California. Chickens fed upon by Cx. tarsalis developed an antibody response that was proportional to the amount of exposure. Cross-reactivity between sera from Cx. tarsalis–exposed chickens and SGAs from Culex pipiens quinquefasciatus, Culex pipiens pipiens, Ochlerotatus melanimon, and Ochlerotatus sierrensis was likely due to shared SGAs among these species. This serologic assay for mosquito exposure could be used to evaluate the sensitivity of sentinel flocks for detecting arboviral activity.

Saliva was collected from 4 species of mosquitoes intrathoracically inoculated with West Nile virus (WNV). The amount of infectious virus in the saliva was quantified by plaque assay and the number of WNV genomic equivalents (GE) was measured by reverse transcriptase–polymerase chain reaction. Ochlerotatus triseriatus had the greatest mean amount of infectious virus per saliva collection, followed by Aedes albopictus, Culex pipiens, and Cx. quinquefasciatus. The mean GE/saliva collection was also greatest in Oc. triseriatus, followed by Cx. quinquefasciatus, Cx. pipiens, and Ae. albopictus. The variance of log GE/saliva collection for Ae. albopictus was significantly lower than the variance for the other 3 species. This study provides a basis for comparing this component of vector competence and for determining the amounts of virus inoculated into vertebrates in experimental host competence studies.

Persistence, wash-resistance, and shelf life of mosquito nets treated with a water-dispersible tablet formulation of synthetic pyrethroid insecticide deltamethrin (K-O TAB^®) at 25 mg/m² was evaluated against malaria vectors in India. During June 2001, treated and untreated polyester, nylon, and cotton nets were separately distributed in 3 villages and cone bioassays were performed on Anopheles culicifacies and An. stephensi 1 day after treatment and thereafter every month for 12 months. The mosquitoes were exposed for 3 min on the nettings (treated and unwashed, or treated and washed once or twice in 3 months, and untreated) and knock-down (1 h) and 24 h postexposure mortality were recorded. Unwashed polyester nets, and those washed once 1 month after treatment, gave 100% mortality in An. culicifacies for 6 months. A 2nd wash at 3 months after treatment marginally reduced the insecticidal action. Anopheles stephensi was fully susceptible up to 4 months when exposed to unwashed nets but washing considerably reduced insecticidal action (65–78% after 2 washes). Treated nylon and cotton nets were effective for 4 months on both vectors. Treated nets kept on shelf retained 100% efficacy for 10 months. Overall, the treated nets gave a considerably long persistence of insecticidal action even after a single wash. Treated polyester nets were found most effective. Compared with our earlier experiences of using liquid formulations, the tablet formulation is likely to have a better community acceptance in treating nets.

To determine the feasibility of microbiological control of chironomid larvae in water sources for the city of Shenzhen, China, the toxicity characteristics of Bacillus thuringiensis var. israelensis (Bti) IPS82 on Chironomus kiiensis Tokunaga were studied. Tests on fermentation products of IPS82 showed good correlations between toxicity, cell density, dissolved oxygen, and the spore-forming phase. In this study, bioassays were carried out with different stage larvae. Results showed that the LC₅₀s (24 h postexposure) were 8.2, 15.2, 24.7, and 38.6 mg/liter for the 1st, 2nd, 3rd, and 4th instars, respectively. Tests on environmental factors influencing toxicity of Bti to C. kiiensis showed that sunlight is the most important factor, shortening the half-life of Bti from 21 days in dark to 10 days under sunlight. Temperature variations (15–30°C) caused no impact on toxicity, but a 16% increase in larval mortality was observed at 35°C. The toxicity of IPS82 was greatest at a pH of 7. In field trials, dosages above 100 mg/liter were effective in the control of C. kiiensis. Our study indicated that it is feasible to use Bti to control C. kiiensis in city source water.

A Klun & Debboun (K&D) test module, previously developed and used for quantitative measurement of the efficacy of mosquito repellents on human volunteers, was adapted for in vitro evaluation of repellents by coupling the module with a membrane-blood reservoir. Performance of Deet, Bayrepel^®, and SS-220 insect repellents in the new in vitro system was compared with their performance on humans against mosquitoes using our standard in vivo system. For each compound, in vitro dose–response assays were conducted with compounds applied to cloth positioned over blood reservoirs covered with Baudruche membrane against Aedes aegypti. The repellents were also tested in vitro against Anopheles stephensi and Ae. aegypti at a fixed dose of 24 nmol compound/cm² cloth over the Baudruche and Edicol collagen membranes. Concurrently, the repellents were tested at the fixed dose using the K&D module on human volunteers. The observed proportions of both mosquito species deterred from biting in the fixed doses in the in vitro assays were similar to those obtained using humans, being clearly able to distinguish controls from repellents, and differing only in the ranking of the effectiveness of some of the repellents. Dose–response relationships of the in vitro and in vivo systems were also very similar, although not directly comparable because the data were not collected concurrently. This new in vitro assay system can be used in high throughput screening of compounds to identify new repellents having potential for use as topical mosquito repellents on humans.

We previously determined that physiological resistance in a laboratory-selected pyrethroid-resistant Anopheles minimus species A Theobald mosquito is associated with increased detoxification via a P450-mediated mechanism. A CYP6 gene, CYP6AA3, was subsequently cloned and found overexpressed in 2 resistant mosquito generations (F₁₃ and F₁₉). We report herein the cloning of CYP6P7 and CYP6P8 genes with full coding sequences from the same An. minimus mosquito colony strain. CYP6P7 and CYP6P8 encode proteins, each with 509 amino acids. CYP6P7 had the closest (81%) amino acid identity with Anopheles gambiae CYP6P2. CYP6P8 genes had 79% identity with An. gambiae CYP6P1. Using semiquantitative reverse transcription-polymerase chain reaction analysis, the mRNA expression level of CYP6P7 presented ~ 2- and 4-fold increases in F₁₉ and F₂₅ deltamethrin-resistant populations, respectively, compared with the parent susceptible strain. CYP6P8 mRNA expression levels were not significantly different between the 3 filial generations. The overexpression of CYP6AA3 mRNA was greater than that of CYP6P7 in F₁₉ and F₂₅ resistant populations. The relative increase of both CYP6AA3 and CYP6P7 mRNA was correlated with increased resistance to deltamethrin in An. minimus.

Five monoterpenes (carvacrol, p-cymene, linalool, α-terpinene, and thymol) derived from the essential oil of thyme (Thymus vulgaris) were examined for their repellency against the mosquito Culex pipiens pallens. All 5 monoterpenes effectively repelled mosquitoes based on a human forearm bioassay. α-Terpinene and carvacrol showed significantly greater repellency than a commercial formulation, N,N-diethyl-m-methylben-zamide (deet), whereas thymol showed similar repellency to that of deet. The duration of repellency after application for all these monoterpenes was equal to or higher than that of deet. These findings indicate that a spray-type solution containing 2% α-terpinene may serve as an alternative mosquito repellent.

Studies were carried out on the bioefficacy and residual activity of Bacillus thuringiensis israelensis H-14 (Bti) (water-dispersible granules of VectoBac ABG 6511 and liquid formulations of VectoBac 12AS) and pyriproxyfen (insect growth regulator, Sumilarv 0.5%) as direct applications for control of larvae of Aedes aegypti and Aedes albopictus. Two dosages of each Bti formulation (285 and 570 international toxic units [ITU]/liter) and the integration of both Bti formulations and pyriproxyfen were used for residual tests with 45-liter earthen jars for a period of 4 wk. In 1 test series, the treated water was replenished daily with 6 liters of seasoned untreated water. In the 2nd test series, the water in the jars was topped up to the 40-liter level during evaluation. Neither Bti formulation remained effective for a full week. Water-dispersible Bti granules provided effective initial control activity against Ae. aegypti and Ae. albopictus for both test designs (with replenishment and without replenishment of water). The higher dosage (570 ITU/liter) for both Bti formulations was only partially effective at the end of 1 wk after being diluted. After 1 wk, water-dispersible Bti granules provided greater larval mortality than did liquid Bti formulation against both mosquito species when integrated with pyriproxyfen. Pyriproxyfen (79.5 and 159 mg/liter) on its own showed low larvicidal activity but provided very effective control of adult emergence. In this study, integration of Bti (285 and 570 ITU/liter) with pyriproxyfen (79.5 mg/liter) extended the duration of partial larval control somewhat, but live larvae persisted throughout the 4-wk test. The integration effect was more obvious when water-dispersible Bti granules were integrated with pyriproxyfen than when liquid Bti was used. Integration of Bti with pyriproxyfen had a negative effect on adult emergence, which was completely inhibited by pyriproxyfen after day 1. Daily replenishment of water increased Bti activity and provided slightly better larval control. Aedes albopictus and Ae. aegypti were both completely susceptible to the higher concentration of Bti and pyriproxyfen in both test designs (with replenishment and without replenishment of water).

Biting insects were sampled to investigate the cause(s) of dermatitis (putative Culicoides hypersensitivity [CHS]) on horses on the Palos Verdes Peninsula, Los Angeles County, California. Suction traps baited with CO₂ were operated at 5 sites from April 2002 to August 2003, supplemented by sampling from horses. Six species of Culicoides, 7 species of mosquitoes, and occasional Simulium and Stomoxys were collected in traps. Culicoides sonorensis was the most common midge trapped, although C. obsoletus and C. freeborni also were collected repeatedly. Insects from the belly region of horses in spring (peak dermatitis period) were mostly C. obsoletus, which were far more abundant than indicated by CO₂-baited suction traps. The predominant mosquito was Culiseta incidens; Culex quinquefasciatus and Cx. tarsalis also could be common, depending on the site. Mosquitoes, particularly Cs. incidens, were more abundant the 2nd year (normal rainfall), whereas C. sonorensis and C. freeborni were more abundant the 1st year (drought period). Culicoides obsoletus, supplemented by C. sonorensis, is regarded as a primary suspect causing CHS in this area.

The larval habitat of Verrallina lugubris (Barraud) is defined based upon collection of 648 larvae from swamp pools from January to March 1998 in Pichavaram mangrove forest, and 125 larvae during September 1997 in Maravakadu mangrove forest in the eastern coast of South India. Salinity of the larval habitat ranged from 12,150 to 24,500 mg/liter in Pichavaram and from 11,600 to 13,000 mg/liter in Maravakadu. Associated mosquito species were Culex sitiens Wiedemann, Ochlerotatus portonovoensis (Tewari and Hiriyan), and Anopheles subpictus Grassi. The chaetotaxy of field-collected larvae of Ve. lugubris is presented.

A limited survey was conducted in 2003 to determine if Ochlerotatus japonicus was spreading outside of King County, Washington. Ochlerotatus japonicus was found in north-central Pierce County and west-central Snohomish County. These collections represent county records. An additional site was reported from King County. Ochlerotatus japonicus is established and spreading to other areas of Washington.

Larvae of Ochlerotatus thibaulti Dyar and Knab have not been reported in New York State or New England, but adult records suggest that breeding populations are present. In 2003 and 2004, larval Oc. thibaulti were collected at 3 sites upstate near the Catskill Mountain region in Lomontville, NY. This is the 1st record of Oc. thibaulti collected in New York and New England. Larvae were found in a variety of subterranean habitats within and near semipermanent woodland pools, including under hummocks and in deep and shallow depressions of upturned trees. No immatures were observed after late June. Larvae of Culiseta melanura were found in the same habitats in the early spring and later in the season after Oc. thibaulti had emerged.

Since July 2002, ongoing surveillance efforts have been conducted to determine potential vectors of West Nile virus (WNV) and Saint Louis encephalitis virus (SLEV) in the mosquito population occurring in Lubbock County, Texas. Adult mosquitoes collected in Lubbock County during 2002 and 2003 represented 7 genera, with Culex tarsalis and Ochlerotatus sollicitans being the predominant species collected. Mosquitoes were initially screened for WNV and SLEV by using the VecTest™antigen panel assay. Positive VecTest results were confirmed by reverse transcriptase–polymerase chain reaction. West Nile virus–positive pools of mosquitoes were detected in 2002 and 2003, with the majority of the positive pools consisting of Cx. tarsalis. None of the mosquito pools tested positive for SLEV.

This document describes the results of collaborative trials between St. Tammany Parish Mosquito Control, ADAPCO, Inc., and the Navy Disease Vector Ecology and Control Center, Naval Air Station, Jacksonville, FL. These tests provide data on the aerial optimization testing of Dibrom 14 Concentrate adulticide. During the week of June 17, 2002, 1 canopy penetration and 3 optimization studies were conducted in St. Tammany Parish, LA, using a Britton Norman twin turbine Islander equipped with 10-800067 flat fan nozzles. Dibrom 14 Concentrate (AMVAC Chemical Corp., Los Angeles, CA) was applied at 3.12 liter per min from a release height of 60.96 m above ground level (agl) at 140 kts indicated airspeed. This resulted in an application rate of 0.65 oz/acre.

A mosquito trap support pole constructed from polyvinyl chloride and aluminum pipes was designed to hang a Centers for Disease Control and Prevention miniature light trap and dry ice container. Miniature light traps normally hang from tree branches. The trap support pole is designed to hang traps and dry ice bait in areas where no suitable trees exist.