The Susceptibility and Behavioral Response of Anopheles Albimanus Weidemann and Anopheles Vestitipennis Dyar and Knab (Diptera: Culicidae) to Insecticides in Northern Belize, Central America
UNIFORMED SERVICES UNIV OF THE HEALTH SCIENCES BETHESDA MD DEPT OF PREVENTIVE MEDICINE AND BIOMETRICS
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During a 9-month study 1995-1996 in Caledonia Village, northern Belize, anopheline mosquitoes collected off human-bait and from experimental huts were evaluated for their susceptibility and behavioral responses to DDT and deltamethrin. Adult Anopheles albimanus, Anopheles vestitipennis, and Anopheles crucians were completely susceptible at diagnostic dosages for DDT 4.0 and deltamethrin 0.025 using the standard WHO susceptibility testing method. Dose response probit analysis indicated low heterogeneity for all 3 populations response to DDT and deltamethrin. Behavioral responses were measured using excito-repellency ER boxes allowing either direct contact irritancy or noncontact repellency to be observed. Use of ER boxes produced strong behavioral avoidance responses with DDT and deltamethrin contact irritancy tests during 60-minute exposure for An. albimanus and An. vestitipennis compared to controls and noncontact trials. A significant repellency response was noted for both species during the 5-hour noncontact tests compared to controls. Six and 12-hour human-landing collections HLC within and outside two experimental huts, before and after DDT spraying, showed An. albimanus to be predominantly exophagic, whereas An. vestitipennis more readily entered the huts to feed on humans. Five, 12-hour evening collections were carried out 12 weeks post-spray. Early evening feeding patterns within the sprayed hut remained similar to the controls, but resting behavior on wall surfaces was greatly diminished in the sprayed hut. Normal indoor-entering females exited the sprayed hut sooner, and biting in the sprayed hut rapidly declined after 2300 hours. Overall, the number of entering and biting Anopheles over the 12-hour evening period was significantly less than that seen in the controls. The results indicate that the continued use of indoor residual insecticide spraying still bears merit as a means of decreasing the transmission of malaria in northern Belize.
- Medicine and Medical Research