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ABSTRACT: Escape responses of mated and unmated nulliparous Aedes aegypti mosquitoes were compared using three different concentrations of deltamethrin in the presence or absence of a live animal host using an excito-repellency (ER) test system. Both insecticide contact (excitation) and non-contact (repellency) test configurations were compared. For contact trials, mated mosquitoes showed similar escape movements among the three concentrations when host stimuli were absent. Significant differences in responses were seen between the lower concentrations of (LC50 and LC75) deltamethrin with and without hosts present (P<0.05). Presence or absence of host stimuli produced no significant differences in escape response for unmated females when exposed to the highest concentration (LC90) of deltamethrin. Our findings indicate that as deltamethrin concentrations decrease to sublethal levels, mating status and host cues play a more significant role in escape behavior. Therefore, insemination can influence the outcome of feeding success and flight movement of nulliparous female Ae. aegypti in contact with deltamethrin and in the presence of live host stimuli. The ER assay system serves as a useful tool for observing excitation and repellency responses of Ae. aegypti to insecticides in the presence or absence of other environmental and biological cues that can affect mosquito behavior. Journal of Vector Ecology 36 (2): 361-372. 2011.
Keyword Index: Aedes aegypti, deltamethrin, host stimuli, feeding responses, excitation, repellency.
INTRODUCTION
Despite decades of organized malaria and dengue control activities, both diseases remain major health concerns in Thailand (MOPH 2009). Because no effective and acceptable vaccine or medical treatment is currently available for combating dengue (and Chikungunya virus), the control of these diseases in Thailand has focused primarily on the monitoring and reduction of the mosquito vectors. Aedes aegypti is a highly anthropophilic species and often resides in and near human dwellings preferentially feeding on humans (Gubler 1997, Thavara et al. 2001, Suwonkerd et al. 2006). This species can utilize many types of artificial and natural container habitats for oviposition and larval development, making source reduction as a method of control difficult. Other methods to prevent dengue transmission are to reduce human-vector contact using insecticides that attack the adult mosquito. Synthetic insecticides, particularly pyrethroids, have been used extensively (especially during high transmission periods or outbreaks) to control dengue vector mosquitoes in Thailand (Chareonviriyaphap et al. 1999,...