ARS | Publication request: Effects of sublethal pyrethroid exposure on host-seeking behavior of female mosquitoes

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 20, 2011
Publication Date: September 20, 2011
Citation: Cohnstaedt, L.W., Allan, S.A. 2011. Effects of sublethal pyrethroid exposure on host-seeking behavior of female mosquitoes. Journal of Medical Entomology. 36(2):1-9.

Interpretive Summary: Although pesticides are designed to kill mosquitoes, not all mosquitoes die when they contact insecticide treated surfaces or droplets of pesticide in the air. Some mosquitoes have resistance and others do not receive enough of the toxicant to die. A sublethal exposure to these neurotoxic compounds cause permanent problems with the insect nerves. This study by scientists at the USDA, ARS, Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL, examines how three species of mosquitoes are behaviorally different when searching for blood meals and how these behaviors change 24 hours after being exposed to a quantity of insecticide that will kill 25% of the treated individuals. Mosquitoes treated with pesticides in general flew slower, spent more time in flight, and turned more frequently. This indicates surviving mosquitoes have a more difficult time using their nervous system when orienting towards hosts after receiving a dose of pyrethroid insecticide.

Technical Abstract: Adult mosquito control consists of residual application on surfaces and aerial spraying often using pyrethroids, however, not all insects contacting insecticides are killed. Sublethal exposure to neurotoxic compounds can negatively affect sensory organs and reducing the insect’s efficiency of host locating. Flight tracks of host-seeking female Culex quinquefasciatus, Anopheles albimanus, and Aedes aegypti in a wind tunnel were video recorded to compare activation to host seeking and patterns of flight orientation. During host-seeking flights, the three 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 neurotoxicants 24 hours post-exposure. Significant reductions in activation to flight and flight direction were observed in mosquitoes exposed to pesticide. Additionally, pesticide-treated mosquitoes flew significantly slower and turned more frequently.