Description and use of the Harris County gravid trap for West Nile virus surveillance 2003-06

The Harris County Gravid Trap (HCGT) used for West Nile virus (WNV) surveillance from 2003-06 is described. The HCGT collected 1,918,483 Culex quinquefasciatus females (over 36,627 periods), with 466,296.37 (8,452.74) yearly. Only 48,094 Aedes albopictus females (over 15,139 periods) were collected, with 10,277.79 (3,260.33) yearly. The highest mosquito production occurred in July for Cx. quinquefasciatus (63,851.25 +/- 0.13), and for Ae. albopictus (2,981.80 +/- 0.09). Integrating gravid traps within our program has increased our ability to detect WNV efficiently in both species.     

West Nile virus-infected mosquitoes, Louisiana, 2002

Human cases of West Nile virus (WNV) disease appeared in St. Tammany and Tangipahoa Parishes in southeastern Louisiana in June 2002. Cases peaked during July, then rapidly declined. We conducted mosquito collections from August 3 to August 15 at residences of patients with confirmed and suspected WNV disease to estimate species composition, relative abundance, and WNV infection rates. A total of 31,215 mosquitoes representing 25 species were collected by using primarily gravid traps and CO2-baited light traps. Mosquitoes containing WNV RNA were obtained from 5 of 11 confirmed case sites and from 1 of 3 sites with non-WNV disease. WNV RNA was detected in 9 mosquito pools, including 7 Culex quinquefasciatus, 1 Cx. salinarius, and 1 Coquillettidia perturbans. Mosquito infection rates among sites ranged from 0.8/1,000 to 10.9/1,000. Results suggest that Cx. quinquefasciatus was the primary epizootic/epidemic vector, with other species possibly playing a secondary role.     

Differential predation of the planarian Dugesia tigrina on two mosquito species under laboratory conditions

Two experiments were performed on the predation of the planarian Dugesia tigrina (Girard) upon 2 mosquito prey species, Aedes albopictus and Culex quinquefasciatus. Bioassays were carried out in sectioned tires with 2 liters of water. In the 1st experiment, predation was evaluated using 4, 8, and 12 mature planarians against 40 2nd-stage larvae of each mosquito species alone. In the 2nd experiment, the same 3 predator densities were used with a pool composed of 20 2nd-stage larvae of each mosquito species. In the 1st experiment, final corrected mortality of Ae. albopictus reached 89.1, 98.8, and 99.6% and final corrected mortality of Cx. quinquefasciatus reached 29.4, 48.0, and 53.0%, respectively, with 4, 8, and 12 planarians. In the 2nd experiment and when subjected to the density of 4 planarians, Ae. albopictus was more susceptible to predation, with a selectivity index of 0.87, whereas this index was 0.13 for Cx. quinquefasciatus. Predation was more intensive during the 1st 4 days of the experiments, when most larvae were in the 2nd and 3rd stages. We observed that Cx. quinquefasciatus larvae were faster than Ae. albopictus in reacting to planarian contacts, resulting in more success in escaping from the predator attacks.     

Efficacy evaluation of a fumigant containing permethrin and deltamethrin against vector mosquitoes

The efficacy of a new smoke-generating formulation (fumigant), containing the active ingredient permethrin (69 g/kg) and deltamethrin (3.9 g/kg) per cartridge, was evaluated against adult female Anopheles albimanus, Aedes aegypti, and Culex quinquefasciatus in a large vehicle storage building (22 x 13 x 4.5 m3), Florida, U.S.A., and against Cx. pipiens complex and Ae. albopictus in a furnished apartment (12 x 7 x 3.5 m3) in Israel. In the storage building, the use of 2 fumigant cartridges resulted in 100% mortality for all 3 species in 15 min. Using 1 cartridge resulted in 100% mortality in An. albimanus, 98% in Ae. aegypti, and 97% in Cx. quinquefasciatus in 15 min; and 100% mortality for both Ae. aegypti and Cx. quinquefasciatus at 30 min. In the apartment in Israel, both Ae. albopictus and Cx. pipiens showed 100% mortality when exposed to the fumigant cartridge for 15 min. Based on these preliminary data, the test formulation (fumigant) could be a valuable tool for controlling mosquitoes.     

广东省蚊虫感染沃尔巴克氏体初步调查研究

目的 了解广东省蚊虫种群中沃尔巴克氏体（Wolbachia）的分布及其基因型别.方法 利用Wolbachia的wsp基因序列建立PCR检测方法,对蚊科中库蚊属、伊蚊属、阿蚊属和按蚊属部分蚊虫种类进行检测,同时利用Mega 5.2软件对所获基因序列进行系统分析.结果 分别从致倦库蚊、骚扰阿蚊、白纹伊蚊及未分型蚊种中检测到12条目的基因序列,其中11条成功进行测序,这些序列分别属于A和B2个超级基因组,分布在5个不同的基因族中.结论 广东省白纹伊蚊、骚扰阿蚊和致倦库蚊中均存在A大组（含2个小组）和B大组（含3个小组）基因型的Wolbachia感染,埃及伊蚊和中华按蚊未检测出Wolbachia.     

West Nile virus in Pakistan. III. Comparative vector capability of Culex tritaeniorhynchus and eight other species of mosquitoes

Eight species of mosquitoes from Pakistan were compared with Culex tritaeniorhynchus as experimental vectors of West Nile (WN) virus. When fed by the membrane or cotton-pledget methods on a dose of WN virus 100% infective for Cx tritaeniorhynchus, 95% and 73% of the females of Cx fuscocephala and Cx pseudovishnui became infected, respectively. Cx quinquefasciatus, Cx univittatus, Aedes albopictus, Ae. caspius, Ae. indicus and Ae. lineatopennis were all significantly less susceptible than Cx tritaeniorhynchus. In agreement with the single dose comparisons, the median per os infective dose of WN virus for Cx fuscocephala, Cx pseudovishnui and Ae. caspius was substantially greater than for Cx tritaeniorhynchus. The median parenteral infective dose for all six species tested was less than 1 SMICLD50. Both Cx tritaeniorhynchus and Cx quinquefasciatus were more susceptible to infection with WN virus when fed on viraemic chickens than when fed on defibrinated blood using cotton pledgets or membranes. After infection by intrathoracic inoculation, only Ae. indicus and Ae. lineatopennis showed a reduced ability to transmit WN virus when compared to Cx tritaeniorhynchus.     

Larval survey of tire-breeding mosquitoes in Alabama

A state-wide survey of tire-breeding mosquitoes in Alabama was conducted in 2004 and 2005. Tire sites in all 67 counties in the state of Alabama were sampled for mosquito larvae. A total of 13,022 mosquito larvae, representing 12 species in 7 genera, was collected. The most frequently collected species were Aedes albopictus (70.4%), Culex territans (8.0%), and Ochlerotatus triseriatus (7.1%). The following species were also collected: Cx. restuans (6.0%), Cx. salinarius (2.7%), Orthopodomyia signifera (2.4%), and Cx. quinquefasciatus (1.4%). Ochlerotatus atropalpus, Toxorhynchites rutilus, Anopheles punctipennis, An. quadrimaculatus, and Psorophora columbiae each represented <1.0% of the total larval collections. No Ae. aegypti or Oc. japonicus were collected from tires during this survey. The first known collection of Ps. columbiae breeding in water-filled tires is reported.     

Insecticidal activity of Valeriana jatamansi (Valerianaceae) against mosquitoes

A root extract of Valeriana jatamansi (code BAL-O) exhibited larvicidal and adulticidal activity against different mosquito species. The median lethal concentration (LC50) of BAL-O against larvae of Anopheles stephensi, Anopheles culicifacies, Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus were 68.1, 42.8, 51.2, 53.8, and 80.6 mg/liter, respectively. The LC50 and the 90% lethal concentration against adult An. stephensi, An. culicifacies, Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus were 0.14, 0.16, 0.09, 0.08, and 0.17 and 0.24, 0.34, 0.25, 0.21, and 0.28 mg/cm2, respectively. The median knock-down time and 90% knock-down time of the fraction were 13, 13, 12, 13, and 18 and 24, 25, 21, 20, and 42 min against An. stephensi, An. culicifacies, Ae. aegypti, An. albopictus and Cx. quinquefasciatus, respectively, using 0.28 mg/cm2 impregnated papers. The median effective time and 90% effective time against An. stephensi at 4 degrees C were 46.6 and 8.7 days, and at 29 degrees C, 25.5 and 5.6 days, respectively. Gas chromatographic-mass spectrometric analysis of BAL-O showed 2-butanone,4-(2,6,6-trimethyl-2-cyclohexen-l-yl) (10.11%), patchouli alcohol (8.55%), cubenol (5.97%), caryophyllene oxide (5.46%), cadinol (5.23%), and aristolene (5.19%).     

Habitat characteristics of larval mosquitoes in zoos of South Carolina, USA

To investigate whether the unique assemblage of habitats in zoos could affect mosquito oviposition behavior and to provide zoos with suggestions for mosquito control, larvae were sampled and associated habitat variables were measured in 2 zoos in South Carolina, U.S.A. Fifty-nine sites were sampled from March 2008 to January 2009. A total of 1630 larvae representing 16 species was collected and identified. The dominant species was Aedes albopictus (46.0%), followed by Ae. triseriatus (23.6%), Culex restuans (12.4%), and Cx. pipiens complex (9.7%). Principal components and multiple logistic regression analyses showed that across both zoos the distribution of Ae. albopictus larvae was predicted by ambient and site temperature, precipitation, dissolved oxygen, and container habitats. The distribution of Ae. triseriatus larvae was predicted by natural containers and shade height < or =2 m. Overall larval mosquito presence (regardless of species) was predicted by ambient and site temperature, precipitation, dissolved oxygen, presence of natural habitats, and absence of aquatic vegetation. Additionally, C8 values of pairwise species associations indicated significant habitat-based relationships between Ae. albopictus and Ae. triseriatus, and Cx. pipiens complex and Cx. restuans. In general, species-habitat associations conformed to previously published studies. Recommendations to zoo personnel include elimination of artificial container habitats, reduction of shade sources < or =2 m over aquatic habitats, use of approved mosquito larvicides, and training in recognizing and mitigating larval mosquito habitats.     

Field comparison of Bermuda-hay infusion to infusions of emergent aquatic vegetation for collecting female mosquitoes

Field experiments were conducted in east-central Alabama in 2003 and 2004 to compare the attractiveness of selected gravid-trap infusions to ovipositing female mosquitoes. Comparisons were made among infusions of the following plants: Bermuda hay, Cynodon dactylon, and 3 species of emergent aquatic plants typical of Culex larval habitats, i.e., soft rush, Juncus effusus; a common sedge, Rhynchospora corniculata; and broad-leaf cattail, Typha latifolia. Experiments were conducted at a site in Lee County, AL, with an abundance of common nuisance mosquitoes, including Culex quinquefasciatus and Aedes albopictus. Carbon dioxide-baited miniature light traps were operated concurrently with gravid traps to provide an activity index of mosquito species at the site. Gravid traps with hay infusion collected the greatest numbers of Cx. quinquefasciatus and Culex restuans females (2003). The results indicate that hay infusion is highly attractive to Cx. quinquefasciatus and is the infusion of choice for collecting females of this species in gravid traps. In the case of Ae. albopictus, infusions were not determined to be significantly different from one another in their attractiveness to gravid females. In general, females of Cx. quinquefasciatus and Cx. restuans demonstrated selectivity when choosing an oviposition site, whereas Ae. albopictus females did not. Factors associated with the oviposition biology of the latter species most likely account for their lack of preference for any single infusion type.     

Residual effectiveness of three pyrethroids on vegetation against adult Aedes albopictus and Culex quinquefasciatus in screened field cages

The residual effectiveness of pyrethroid-treated vegetation as a barrier against female host-seeking Aedes albopictus and Culex quinquefasciatus was evaluated in large screened-cage field tests for 12 wk. Individual potted southern wax myrtle (Myrica cerifera L.) plants were treated with either beta-cyfluthrin (Tempo SC Ultra), lambda-cyhalothrin (Demand CS), or tau-fluvalinate (Mavrik Perimeter) at maximum label rates. Suction mosquito traps (MMX) baited with carbon dioxide placed near plants treated with tau-fluvalinate provided significant overall reduction (approximately 62-80%) of mosquitoes through 2 wk compared with untreated plants. Overall percent knockdown/mortality from excised-leaf bioassays was similar to suction-trap reduction data. However, knockdown/mortality in leaf bioassays was greater for Ae. albopictus than for Cx. quinquefasciatus, whereas no such effect was observed in trap collections. Mosquito abundance in MMX collections near plants treated with beta-cyfluthrin provided similar levels of reduction as tau-fluvalinate-treated plants through 1 wk and 3-4 wk after treatment. Leaf toxicity generally provided approximately > 90% knockdown/mortality on beta-cyfluthrin treated leaves throughout the study. Generally, no consistent difference in trap reduction or weekly knockdown/mortality in leaf bioassays was observed between either mosquito species. Plants treated with lambda-cyhalothrin provided significantly greater overall reduction of mosquitoes (75-83%) from MMX collections for the first 5 wk compared with untreated plants. Knockdown/mortality levels and duration of leaf toxicity from lambda-cyhalothrin- treated leaves was similar to that of beta-cyfluthrin, with no consistent differences between mosquito species.     

Relative abundance and blood feeding behavior of nocturnally active culicine mosquitoes in western Kenya

At 2 sites in western Kenya targeted for future malaria vaccine trials, adult culicine mosquitoes were sampled over one year by 5 collection techniques to assess human exposure to potential vectors of pathogens other than malaria. Collections included 20,910 females representing 19 species in Kisian and 4,312 females of 11 species in Saradidi. Common species in Kisian included Culex quinquefasciatus (71.4%), Mansonia uniformis (15.8%), Ma. africana (6.2%), Aedes mcintoshi (2.0%), Coquillettidia fuscopennata (1.9%) and Ae. ochraceus (1.8%). Common species in Saradidi included Cx. quinquefasciatus (92.7%), Cx. nebulosus (4.5%) and Ma. uniformis (1.0%). Human-bait collections identified 16 man-biting culicine species in Kisian and 9 in Saradidi. Man-biting rates at Kisian for the 5 most common species were 1.8, 14.6 and 13.5 times higher than at Saradidi for indoor, outdoor and tent collections, respectively. Exposure indoors was estimated to be 1,277 bites/man/year at Kisian and 720 at Saradidi. Blood meal identification for 1,083 mosquitoes confirmed that the common culicine species feed primarily on humans and cows.     

Mosquitoes potential vectors of canine heartworm in the Northeast Region from Brazil

INTRODUCTION: In some coastal districts of S?o Luís, capital of the state of Maranh?o, Brazil, the prevalence of Dirofilaria immitis is more than 40% in house dogs. Natural potential vectors, as found in other areas of Northeastern Brazil, are unknown. The aim of this study was to identify probable vectors of the disease. METHODS: Mosquito catches were performed at a coastal, district Olho d'Agua, in S. Luís, to look for local potential vectors. Captures were carried out monthly, from March 1996 to May 1997, outdoors, having a man and a dog as baits. Mosquitoes were dissected for D. immitis larvae. RESULTS: A total of 1,738 mosquitoes belonging to 11 species were collected. Culex quinquefasciatus, the only species collected every month, was more frequently in the dry season. It accounted for 54.5% of the total, followed by Aedes albopictus (20. 3%), Ae. scapularis (11%) and Ae. taeniorhynchus (11%). D. immitis larvae were detected in 0.1% of the Cx. quinquefasciatus dissected (L3 in the Malpighian tubules) and 0.5% of the Ae. taeniorhynchus (L2 in the Malpighian tubules). CONCLUSION: Ae. taeniorhynchus and Cx. quinquefasciatus are considered natural potential vectors of the canine heartworm in S?o Luís. The role of Cx. quinquefasciatus as primary vector of D. immitis, however, needs further evaluation.     

First record of Ascogregarina taiwanensis (Apicomplexa: Lecudinidae) in North American Aedes albopictus

Aedes albopictus collected in the East St. Louis, Illinois, area were found infected with the gregarine protozoan, Ascogregarina taiwanensis. Infection rates varied from 67 to 95% at 4 sites and 0 to 10% at 2 others. Lower infection levels were found in Ae. epactius (42%) and Culex restuans (one larva). Four mosquito species were cross-infected in the laboratory with gregarines isolated from field-collected hosts. Aedes atropalpus was 90% susceptible to A. taiwanensis (100% in Ae. albopictus), with abnormal development and some melanization of trophozoites and gametocysts. In Ae. aegypti and Cx. restuans, the experimental infection was much lower (12-56%) and exhibited abnormalities similar to the Ae. atropalpus infections. Ascogregarina oocysts recovered from both Ae. aegypti and Ae. atropalpus hosts were subsequently infective to Ae. albopictus. In Ae. triseriatus, A. taiwanensis infection was very low (25%, 1-2 trophozoites per larva); gametocysts were not observed nor were infectious oocysts obtained. We conclude that A. taiwanensis, newly introduced to the USA with Ae. albopictus, can develop in 4 indigenous mosquito species and can produce deleterious effects in at least 2, Ae. aegypti and Ae. atropalpus.     

Effectiveness and residual activity comparison of granular formulations of insect growth regulators pyriproxyfen and s-methoprene against Florida mosquitoes in laboratory and outdoor conditions

Effectiveness and residual activity tests of granular formulations of 2 insect growth regulators (IGRs), s-methoprene and pyriproxyfen, against laboratory-reared larvae of 5 colonized mosquitoes, Aedes aegypti, Aedes albopictus, Aedes taeniorhynchus, Anopheles quadrimaculatus, and Culex nigripalpus, were conducted in the laboratory and outdoors in plastic tubs. Culex quinquefasciatus was exposed to these two IGRs in the laboratory only. Each IGR formulation was applied at 0.02 and 0.05 ppm active ingredient (Al) against 5 of the 6 mosquito species both in the laboratory and the outdoor evaluations, whereas Cx. quinquefasciatus was exposed to 0.2 and 0.4 ppm AI of s-methoprene, and 0.1 and 0.2 ppm AI of pyriproxyfen in the laboratory. s-Methoprene at 0.02 and 0.05 ppm AI resulted in variable levels (<39-100%) of inhibition of adult emergence in the 5 species monitored for 6 weeks after treatment under both test conditions. Aedes taeniorhynchus was the most susceptible to s-methoprene in terms of initial and residual activity. Culex quinquefasciatus and Ae. albopictus were the most tolerant to s-methopene, with maximum emergence inhibitions amounting to 84% in Cx. quinquefasciatus at 0.4 ppm and 44.3% in Ae. albopictus at 0.05 ppm during the 1st week in the laboratory. Pyriproxyfen at comparable treatment rates to s-methoprene caused very high levels (>80-100% in most cases) of initial and residual emergence inhibitions of the tested species in the laboratory as well as outdoors. In several species, pyriproxyfen induced complete inhibition of adult emergence for several weeks after treatment, even at the lower rate of 0.02 ppm. The World Health Organization has recently recommended the use of pyriproxyfen for the control of some mosquito species at specified rates in certain habitats.     

The association of Aedes aegypti and Ae. albopictus in Allende, Nuevo León, Mexico

The recent appearance of Aedes Stegomyia albopictus (Skuse) in Nuevo León (NL) worries health officials. It is a vector of dengue fever in Asia and is more resistant to lower temperatures than Ae. aegypti. The objective of this study was to learn about some ecological parameters of Ae. albopictus and their association with Ae. aegypti, and other culicids in Allende, NL, Mexico, during 1999. Allende is a small town close to metropolitan Monterrey, which has 4 million inhabitants. The design was random with monthly sampling of 175 ovitraps. Chi-square analyses were performed with data of presence, absence, frequency, and relative abundances. During the study, the species Culex tarsalis (Coquillet), Cx. thriambus (Dyar), Cx. pipiens (Linnaeus), Cx. coronator (Dyar and Knab), Ae. albopictus, Ae. aegypti, Toxorhynchites rutilus (Coquillet), and Ae. triseriatus (Say) were found. April is the month for large numbers of mosquito species. September had the highest populations in positive ovitraps (66.67%), followed by July (63.27% of traps). Aedes aegypti was the most abundant (65.13%), followed by Ae. albopictus (19.71%). Both Ae. albopictus and Ae. aegypti were found from April until December. Aedes aegypti was more abundant than Ae. albopictus, except in August, when they were similar (chi2 = 0.197, P < 0.05). We found significant association between the presence of both species for every study month (chi2 = 9.837, P < 0.05), with a contingency coefficient of 0.247. September and November were the months having the most mosquitoes in this association. Only considering Ae. albopictus, more were found in ovitraps in July (34.6%), followed by September (33.3%). However, its presence was not significant throughout the year. Of 2 zones, in town and at the river, prevalence indicated that Ae. albopictus preferred the river. This mosquito is in its establishment phase in this area and requires further studies.     

Mosquitoes of the mangrove forests of India: part six--Kundapur, Karnataka and Kannur, Kerala

Mosquitoes of 26 species belonging to 16 subgenera and 11 genera were recorded in the Kundapur mangroves of Karnataka, and 17 species belonging to 11 subgenera and 7 genera were recorded in the mangroves of Kannur, Kerala along the west coast of India. Genera recorded were Aedes, Anopheles, Armigeres, Culex, Heizmannia, Lutzia, Mansonia, Ochlerotatus, Tripteroides, Uranotaenia, and Verrallina. Species common to both mangrove forests were Ae. albopictus, Ae. vittatus, An. jamesi, Ar. subalbatus, Cx. gelidus, Cx. infantulus, Cx. pseudovishnui, Cx. sitiens, Cx. tritaeniorhynchus, Oc. wardi, Ur. atra, and Ve. luguhris. Tree holes and swamp pools were the common larval habitats, with more species occurring in tree holes in Kundapur than in Kannur. Adults of Ae. albopictus, Ae. vittatus, Ar. aureolineatus, Ar. subalbatus, Cx. bitaeniorhynchus, Cx. sitiens, Ma. uniformis, and Ve. lugubris bloodfed on humans.