The spatial distribution of Aedes aegypti and Aedes albopictus in environmental and geographical zones, e.g., urban-rural, coastal-mountainous, and north-south, was investigated throughout Vietnam. Immature stages were collected from used tires along roads. The effects of regions, seasons, and the degree of urbanization on the density and the frequency were statistically analyzed. Aedes aegypti predominated in the southern and central regions, while Ae. albopictus predominated in the northern region, which may be related to climatic conditions (temperature and rainfall). Larval collection from used tires may be suitable to assess rapidly the current distribution of dengue mosquitoes for estimating health risks and implementing vector control measures.

The seasonality of phlebotomine sand flies was studied in Florida, utilizing colored light-emitting diode- and attractant-baited Mosquito Magnet MM-X traps from September 2006 to September 2008 at San Felasco Hammock Preserve State Park, Gainesville, FL. A total of 6,278 sand flies were collected from 314 actual nights and 1,692 total trap-nights, yielding 3.7 sand flies per trap-night. Lutzomyia shannoni was the predominant species, constituting 55% to 80% of the total sand fly populations collected during the studies. Both L. shannoni and L. vexator populations were highly seasonal and were moderately influenced by weather factors. Lutzomyia shannoni populations peaked in May and showed reduced activity during December, January, and February. This species was active throughout the year and showed positive and negative correlations with average monthly temperature and relative humidity, respectively. Lutzomyia vexator showed peak activity during August and October with an activity lull from December to March. This species showed a positive correlation with average monthly temperature. No correlations were observed with either species for average daily, weekly, or 1- to 8-wk-lagging precipitation, number of rainy days, wind speed, or lunar phases. Lutzomyia shannoni abundance was weakly correlated to L. vexator abundance. No other Lutzomyia spp. were collected during the study.

The blood meal sources of 5 species (Mansonia titillans, Aedes scapularis, Culex quinquefasciatus, Coquillettidia shannoni, and Anopheles peryassui) collected in Conceição do Macacu, in the southeastern Brazilian state of Rio de Janeiro, were examined with the precipitin test. Of the 1,128 mosquitoes collected, 907 (80.4%) reacted to some antisera. Although all 5 species were eclectic in their feeding habits, Ma. titillans and Ae. scapularis fed mostly on birds, while Cx. quinquefasciatus, Cq. shannoni, and An. peryassui fed mostly on bovines. Proportions of mosquitoes feeding on 1 source varied from 60.0% (Ae. scapularis) to 87.7% (Ma. titillans), while that of mosquitoes feeding on >1 source varied from 12.2% (Ma. titillans) to 34.4% (Ae. scapularis). Epidemiological implications of the feeding and their potential involvements in the transmission of arboviruses are commented upon.

The occurrence of multiple pathogens in mosquitoes and birds could affect the dynamics of disease transmission. We collected adult Culex pipiens and Cx. restuans (Cx. pipiens/restuans hereafter) from sites in Wisconsin and tested them for West Nile virus (WNV) and for avian malaria (Plasmodium). Gravid Cx. pipiens/restuans were tested for WNV using a commercial immunoassay, the RAMP® WNV test, and positive results were verified by reverse transcriptase–polymerase chain reaction. There were 2 WNV-positive pools of Cx. pipiens/restuans in 2006 and 1 in 2007. Using a bias-corrected maximum likelihood estimation, the WNV infection rate for Cx. pipiens/restuans was 5.48/1,000 mosquitoes in 2006 and 1.08/1,000 mosquitoes in 2007. Gravid Cx. pipiens or Cx. restuans were tested individually for avian Plasmodium by a restriction enzyme–based assay. Twelve mosquitoes were positive for avian Plasmodium (10.0%), 2 were positive for Haemoproteus, and 3 were positive for Leucocytozoon. There were 4 mixed infections, with mosquitoes positive for >1 of the hemosporidian parasites. This work documents a high rate of hemosporidian infection in Culex spp. and illustrates the potential for co-infections with other arboviruses in bird-feeding mosquitoes and their avian hosts. In addition, hemosporidian infection rates may be a useful tool for investigating the ecological dynamics of Culex/avian interactions.

The predatory ability of adult Japanese diving beetles on 4th instars of the Japanese encephalitis vector mosquito, Culex tritaeniorhynchus, was assessed under laboratory conditions. To determine the differences in the predatory ability among 14 beetle species inhabiting rice fields, the following species were introduced to 10 Cx. tritaeniorhynchus 4th instars in a plastic cup: 5 small-bodied species (<9 mm in body length) comprising Hydroglyphus japonicus, Noterus japonicus, Laccophilus difficilis, Hyphydrus japonicus, and Agabus japonicus; 7 medium-bodied species (9–20 mm in body length) comprising Hydaticus rhantoides, Hydaticus grammicus, Rhantus suturalis, Eretes griseus, Hydaticus bowringii, Agabus conspicuous, and Graphoderus adamsii; and 2 large-bodied species (>20 mm) comprising Cybister brevis and C. japonicus. The average 24-h predation rate was highest in medium-bodied species (>90%), followed by small-bodied species (31%) and large-bodied species (19%). The functional responses to Cx. tritaeniorhynchus larvae of 3 medium-bodied species (H. grammicus, R. suturalis, and E. griseus) were estimated. Eretes griseus exhibited the highest attach rate and shortest prey-handling time, suggesting that medium-bodied diving beetles, especially E. griseus, may be efficient predators of mosquito larvae in rice fields.

In 2002, more than 17,000 mosquito pools collected in Canada (Quebec, Ontario, and Manitoba) were tested at the National Microbiology Laboratory in Winnipeg, Manitoba, for infection with West Nile virus (WNV). Using real-time reverse-transcriptase polymerase chain reaction (RT-PCR), 558 mosquito pools (86% Culex species and 14% other species) had evidence of infection with WNV. Only 30% of the Culex specimens, however, were identified to the species level. In this study, Culex species-specific PCR primers were designed to identify individual mosquitoes and mixed pools of Culex mosquitoes to species. In addition, pools of non-Culex mosquitoes that tested positive for WNV were also screened for Culex DNA to determine the frequency of cross-contamination among mosquitoes of different species. All DNA extracts from 121 Culex and 51 non-Culex pools, previously positive for WNV, were screened, and Culex DNA was detected in approximately 6% of non-Culex pools. This study demonstrates that contamination among mosquito species can occur and emphasizes that precautions should be taken to minimize this potentially confounding effect.

Mass trapping with multiple CO₂- and octenol-supplemented Mosquito Magnet® X traps (MM-X), operated 24 h/day, 7 days/wk, from March through November 2008, at St. Andrews State Park on northwest Florida's Gulf Coast, did not significantly reduce mosquito numbers compared to nontreated control sites. Anopheles crucians, Aedes taeniorhynchus, Culex salinarius, and Culex erraticus were the predominant species. Culex coronator was also collected for the first time in the park. Failure to reduce a late season outbreak of Ae. taeniorhynchus within the trapping area required adulticide application to achieve mosquito control.

The caged mosquito bioassay places the test insects in a mesh cage in the path of an insecticidal space spray to investigate the effect of a machine or chemical type on mosquito mortality. The effects of different mesh densities on mosquito confinement and mortality were investigated. In addition, the predominant pathway for exposure of a caged mosquito bioassay was established. The number of weaves per unit area was the primary parameter for mosquito confinement. Mortality increased with a reduction in mesh density but not with any of the measurable mesh characteristics. There was no correlation between mortality and the wire gauge, the opening size, or the percent openness. It is hypothesized that open area is the predominant parameter and that where the openness is similar, the effects of wire diameter on collection efficiency can be seen. The predominant exposure mechanism was a space spray. The residual tarsal contact had a significant effect on mosquito mortality only after 24 h of exposure. The combined effect of space spray and residual tarsal contact shows a significant increase in mortality after 30 min compared to space spray alone.

The Sacramento and Yolo Mosquito and Vector Control District (SYMVCD, also referred to as “the District”) conducts surveillance and management of mosquitoes in Sacramento and Yolo counties in California. Following an increase in numbers and West Nile virus (WNV) infection rates of Culex tarsalis and Culex pipiens, the District decided on July 26, 2007, to conduct aerial applications of Evergreen® EC 60-6 (60% pyrethrins: 6% piperonyl butoxide) over approximately 215 km² in the north area of Sacramento County on the nights of July 30, July 31, and August 1, 2007. At the same time, the District received notification of the first human WNV case in the area. To evaluate the efficacy of the applications in decreasing mosquito abundance and infection rates, we conducted pre- and post-trapping inside and outside the spray zone and assessed human health risks from exposure to the insecticide applications. Results showed a significant decrease in abundance of both Cx. tarsalis and Cx. pipiens, and in the minimum infection rate of Cx. tarsalis. Human-health risks from exposure to the insecticide were below thresholds set by the US Environmental Protection Agency.

The effectiveness of spinosad for larval mosquito control is summarized based on available published literature and some heretofore unpublished studies. Spinosad is highly active against larvae of all mosquito species tested thus far. It is effective at similar dosages for all larval mosquito instars, with peak cumulative mortality occurring at 72 h posttreatment. More studies are needed to fully define spinosad's ovicidal properties and its impact on the pupal stage. High levels of organic matter and full sunlight are both factors that can negatively impact spinosad efficacy and longevity and should be considered when making use rate and retreatment decisions. Studies clearly show that spinosad technical active ingredient and current crop formulations are suboptimal for larval mosquito control and underrepresent spinosad's true activity. A series of spinosad formulations specialized for larval mosquito control will be sold commercially. Prior to its launch and widespread use, there is a need for additional baseline studies to clarify the natural geographic variation in susceptibility of field mosquito populations. Spinosad represents a new and effective natural product for the integrated management of larval mosquitoes. It possesses a unique mode of action not shared by any other insecticide and is shown to be minimally disruptive to most nontarget species tested thus far at its proposed field use rates.

The records of mosquito species in eastern Washington State are sparse, relative to other areas of the state. To improve the knowledge of mosquito diversity and activity in eastern Washington, mosquito surveillance activities were conducted during the summers of 2007 and 2008, which resulted in the collection of 8 species of mosquitoes from 4 counties where they had not been previously recorded.

The geographical distribution of Aedes pennai, Anopheles galvaoi, Coquillettidia albicosta, Cq. nigricans, Culex usquatissimus, Cx. apicinus, Cx. chidesteri, Cx. coronator s.l., Cx. interfor, Cx. maxi, Cx. pipiens, Cx. saltanensis, Cx. educator, Cx. serratimarge, Cx. theobaldi, Psorophora cyanescens, Ps. cilipes, Ps. cingulata, Ps. pallescens, Uranotaenia lanei, Ur. nataliae, Wyeomyia diabolica, and Wy. melanocephala is extended, including new records for 6 provinces and 2 new records for the country, increasing the number of species in Argentina from 226 to 228.

The seasonal variation in the density of swimming pools and the occurrence of immature mosquitoes in these habitats were studied in the temperate city of Buenos Aires, Argentina. The density of swimming pools was highest in the summer (6.0 pools/ha) when temporal pools predominated; it was lowest in the winter (0.9 pools/ha) when only permanent pools were recorded. The presence of immature stages of mosquitoes was mainly associated with the lack of use and maintenance of the pools in the fall season, when temporal pools were still assembled but not intensively used. Seven mosquito species were recorded, among which Culex pipiens and Culex apicinus were the most frequent.

A colony of Uranotaenia macfarlanei, a frog-feeding mosquito, was established in the laboratory. We report the bionomics of the species, as studied in the laboratory colony and in the field on Ryukyu Island, Japan. These include mating activity, feeding and resting habits, manner of oviposition, and egg, larval, and pupal periods.

Culex pipiens quinquefasciatus were fed blood containing either 7.0 ± 0.1 logs plaque-forming units (pfu)/ml (high dose) or 5.9 ± 0.1 logs pfu/ml (low dose) of West Nile virus and held at extrinsic incubation temperatures (EIT) of 28°C or 25°C. Approximately 20 mosquitoes per dose were collected after incubation periods (IP) of 4, 6, 8, and 12 days postinfection (dpi). Infection rates were influenced by EIT and virus dose but not by IP. Body titer was significantly higher for mosquitoes fed the high dose and held at 28°C at the later IPs (6, 8, and 12 dpi). However, leg titer was significantly higher for mosquitoes at the later IPs but did not differ between EITs or doses. Because infection rates varied with EIT and dose, there is likely a midgut infection barrier influenced by these factors that is not influenced by IP. Dissemination rates were influenced by all 3 factors consistent with the presence of a midgut escape barrier. Dissemination rate, body titer, and leg titer were dependent on IP, indicating the need to investigate multiple time points in vector competence studies to elucidate critical events in infection and dissemination.

We present a simplified method for the collection of mosquito saliva to determine Culex pipiens quinquefasciatus transmission of West Nile virus that can be used for experiments requiring large sample sizes.

The abilities of Aedes aegypti and Ae. albopictus females in trespassing 5 different commercial nets, 2 nets impregnated with deltamethrin or permethrin and 3 non-impregnated nets (Guarany, Perame, and Ricca), were compared. The evaluating parameters were their percent trespassing success, the median trespassing time (TT₅₀), and the relation between mosquito wing sizes and their trespassing success. Some mosquito behavioral traits were also observed. The trespassing success, directly related to opening areas, was found to be lower with impregnated nets for both species. The differences between the mosquito species were significant among all the nets except Ricca. Aedes albopictus showed a very high success rate in trespassing the non-impregnated Perame net and a lower success rate in trespassing Guarany. Aedes albopictus also showed a very high success rate in trespassing pyrethroid-impregnated nets. The TT₅₀ values for the Ricca and Guarany nets were not significantly different between the species, but a significantly lower TT₅₀ value was found for the net with the largest opening (Ricca). The smaller wingspan of Ae. albopictus seems to explain the higher trespassing success of this species.

Experiments were conducted to determine the residual efficacy of both a briquette and a granular formulation (2 rates) of a numbered spinosad compound against Psorophora columbiae larvae in small rice plots. Comparisons were also made between the numbered compounds and labeled granular and briquette formulations of methoprene. Both rates of the spinosad granules had the highest initial efficacy (100% control), with the spinosad briquette being the least effective. However, 1 wk after treatment, the spinosad briquette was equally effective to both spinosad granules, suggesting a slow release in the briquette. The experimental briquette and the high rate of the experimental granules had the most residual activity, providing over 80% control for 33 days posttreatment. The granular methoprene formulation was the least residually effective compound, providing only 12% control at 7 days posttreatment.

The original Centers for Disease Control and Prevention (CDC) gravid trap, with its mesh collection bag, can cause considerable damage to the captured mosquitoes. In an effort to reduce this damage and keep costs at a minimum, we modified our existing CDC gravid traps to accept a collection cup from a CDC light trap. This modification allowed for easier transport, freezing, storage, and removal of the mosquitoes. Modifying the CDC gravid traps takes little expertise or resources and can be completed quickly.