Effects of sublethal pyrethroid exposure on the host-seeking behavior of female mosquitoes

A common method of adult mosquito control consists of residual application on surfaces and aerial spraying often using pyrethroids. However, not all insects that contact insecticides are killed. Sublethal exposure to neurotoxic compounds can negatively affect sensory organs and reduce efficiency of host location. Flight tracks of host-seeking female Culex quinquefasciatus, Anopheles albimanus, and Aedes aegypti in a wind tunnel were video-recorded to compare activation of host-seeking and patterns of flight orientation to host odors. During host-seeking flights, all three mosquito species differed significantly in flight duration, velocity, turn angle, and angular velocity. Mosquitoes were then exposed to sublethal levels (LD25) of pyrethroid insecticides to evaluate the effects of the neurotoxicants 24 hours post-exposure. Significant reductions in time of activation to flight and flight direction were observed in mosquitoes exposed to deltamethrin and permethrin. Additionally, pesticide-treated Cx. quinquefasciatus mosquitoes flew significantly slower, spent more time in flight, and turned more frequently than untreated controls.