Field Evaluation of Indoor Thermal Fog and Ultra-Low Volume Applications For Control of Aedes aegypti in Thailand.

Efficacies of a handheld thermal fogger (Patriot™) and a backpack ultra-low volume (ULV) sprayer (Twister™) with combinations of 2 different adulticides (pyrethrin, deltamethrin) and an insect growth regulator (pyriproxyfen) were field-tested and compared for their impact on reducing indoor Aedes aegypti populations in Thailand. The effectiveness of the indoor space sprays was evaluated by sampling the natural Ae. aegypti population in houses and determining their physiological status, by monitoring mortality of sentinel caged mosquitoes (AFRIMS strain) and by assessing larval mortality in laboratory bioassays using water exposed to the spray. A total of 14,742 Ae. aegypti were collected from Biogents Sentinel traps in this study. The combination of ULD® BP-300 (3% pyrethrin) and NyGuard® (10% pyriproxyfen) sprayed either by the Patriot or Twister significantly reduced some Ae. aegypti populations up to 20 days postspray relative to the control clusters. The addition of pyriproxyfen to the adulticide extended how long household mosquito populations were suppressed. In 2 of the 4 products being compared, the Twister resulted in higher mortality of caged mosquitoes compared with the Patriot. However, neither machine was able to achieve high mortality among Ae. aegypti placed in hidden (protected) cages. The larval bioassay results demonstrated that the Twister ULV provided better adult emergence inhibition than the Patriot (thermal fogger), likely due to larger droplet size.

Efficacy of commercial mosquito traps in capturing phlebotomine sand flies (Diptera: Psychodidae) in Egypt.

Four types of commercial mosquito control traps, the Mosquito Magnet Pro (MMP), the Sentinel 360 (S360), the BG-Sentinel (BGS), and the Mega-Catch Ultra (MCU), were compared with a standard Centers for Disease Control and Prevention (CDC) light trap for efficacy in collecting phlebotomine sand flies (Diptera: Psychodidae) in a small farming village in the Nile River Valley 10 km north of Aswan, Egypt. Each trap was baited with either carbon dioxide (CO2) from combustion of butane gas (MMP), dry ice (CDC and BGS traps), light (MCU and S360), or dry ice and light (CDC). Traps were rotated through five sites in a5 x 5 Latin square design, repeated four times during the height of the sand fly season (June, August, and September 2007) at a site where 94% of sand flies in past collections were Phlebotomus papatasi (Scopoli). A total of 6,440 sand flies was collected, of which 6,037 (93.7%) were P. papatasi. Of the CO2-baited traps, the BGS trap collected twice as many P. papatasi as the MMP and CDC light traps, and at least three times more P. papatasi than the light-only MCU and S360 traps (P < 0.05). Mean numbers (+/- SE) of P. papatasi captured per trap night were as follows: BGS 142.1 (+/- 45.8) > MMP 56.8 (+/- 9.0) > CDC 52.3 (+/- 6.1) > MCU 38.2 (+/- 6.4) > S360 12.6 (+/- 1.8). Results indicate that several types of commercial traps are suitable substitutes for the CDC light trap in sand fly surveillance programs.

Relative abundance and species composition of mosquito populations (Diptera:Culicidae) in a La Crosse virus-endemic area in western North Carolina.

Container surveys were conducted in 5 communities on the Cherokee Indian Reservation, an area of western North Carolina endemic for transmission of La Crosse (LAC) virus, to determine the potential for peridomestic mosquito breeding, the relative abundance of mosquito species, and the standing crop of mosquitoes per residence. Eleven species of mosquitoes were collected, but 80.9% of all mosquitoes reared from containers were Aedes triseriatus (Say). All communities averaged > 6 containers per residence, indicating that the potential for mosquito production was high. The Breteau index and mean standing crop of adults per residence in the 5 communities were highly concordant. LAC virus was isolated from 2 pools of 56 female and 36 male Ae. triseriatus adults that were reared from eggs collected by ovitraps. The minimum field infection rate was 0.26 per 1,000 adults tested. Aedes triseriatus, the most frequently collected blood-fed mosquito (98/112 blood-engorged specimens), fed predominantly on dogs (40.4%), rabbits (26.6%), and turtles (22.3%). Only 7.5% of the blood-fed mosquitoes had fed on eastern chipmunks. Peridomestic conditions on the Reservation appear to contribute to the maintenance of LAC virus transmission. Production of Ae. triseriatus occurs in artificial containers discarded around residences, and wooded areas immediately adjacent to residences provide resting cover for mosquitoes as well as suitable habitat for LAC virus reservoir hosts.

Seasonal occurrence and abundance of Aedes triseriatus and other mosquitoes in a La Crosse virus-endemic area in western North Carolina.

The species composition and population abundance of mosquitoes were investigated from May to November in 1989 and 1990 on the Cherokee Indian Reservation, an area of western North Carolina endemic for transmission of La Crosse (LAC) virus. Mosquitoes representing 6 genera and 13 species were collected. Aedes triseriatus was the most abundant species collected, comprising over 98% of mosquitoes collected by ovitrapping and CO2-baited suction trapping, and 88% of resting adults collected by vacuuming vegetation and leaf litter. Culex restuans and Anopheles punctipennis were common but much less frequently collected. Host-seeking and resting Ae. triseriatus were most abundant in early to midsummer, whereas gravid Ae. triseriatus was most active in the fall. The previous occurrence of cases of LAC encephalitis was concordant with the seasonal activity of gravid but not host-seeking or resting Ae. triseriatus.

Seroepidemiology of La Crosse virus infection in humans in western North Carolina.

On the Cherokee Indian Reservation and surrounding area of western North Carolina, an area-wide serosurvey was conducted to determine the prevalence of neutralizing antibody to La Crosse (LAC) virus. A questionnaire was used to identify risk factors important in exposure to virus-infected mosquitoes in populations near the reservation. Of 1,008 serum samples tested, 9.6% were positive for LAC virus antibody. For samples solely collected from on (n = 311) or off (n = 697) the reservation, the prevalence of seropositive samples was 20.6% on the reservation and only 4.7% off the reservation. Seropositivity increased directly with age, indicating that transmission of LAC virus was highly endemic. Age and location residence (on versus off the reservation) were significant risk factors for exposure to LAC virus. Persons on the reservation were 5.5 times more likely to have been exposed to LAC virus than were people who reside off the reservation. An additive increase in risk of 1.5 times over each age group was found, so that the oldest age group ( > or = 75 years) was 7.5 times more likely to have been exposed to LAC virus than was the youngest age group ( < 1-14 years).

Identification of horse flies (Diptera: Tabanidae) by analysis of cuticular hydrocarbons.

Thin-layer chromatography of the cuticular lipids of horse flies from Oklahoma revealed that hydrocarbon was the major lipid class present. The hydrocarbon fraction was composed of n-alkanes and methyl branched alkanes with only a small amount of alkenes present. Gas chromatography of the isolated cuticular hydrocarbons from a single species, Tabanus abactor Philip, showed no major differences in the profiles between individuals or between the sexes. Analysis of extracts of fresh, frozen, and pinned specimens yielded nearly identical hydrocarbon profiles. Profiles of several species were examined and found to be unique for each. Three species with similar morphological characteristics and similar geographical ranges. Tabanus abdominalis F., T. limbatinevris Macquart, and T. sulcifrons Macquart, were differentiated easily by comparison of the hydrocarbon profiles.