Culex quinquefasciatus Mosquitoes Exposed to a Juvenile Hormone Analog may Take a Bloodmeal While Gravid

Abstract

Blood avidity in female mosquitoes has been shown to be regulated by cycles of hormone production that determine both egg development and distinct behaviors. Specifically, juvenile hormone (JH) drives early egg development until a bloodmeal is acquired, and JH titers are positively correlated with active host seeking and blood feeding behaviors. After a bloodmeal, JH levels fall, and female mosquitoes become refractory to host seeking and biting. While JH analogs (JHAs) are commonly used as larvicides for mosquito control, the effects of these compounds on adult mosquitoes are not well understood. If JH levels are directly implicated in blood acquisition, adult exposure to JHAs might cause nonbiting female mosquitoes to take a blood meal. To test this hypothesis, in laboratory experiments we exposed gravid Culex quinquefasciatus mosquitoes to s-hydroprene, a JHA, both through direct topical application and a simulated environmental exposure. We found a significant increase in the likelihood of gravid Cx. quinquefasciatus taking a bloodmeal after exposure to JHAs at levels we hypothesize they may encounter in the field. We also measured the fertility of females that had taken a second bloodmeal while gravid and found a significant negative effect on both the number and hatch rate of eggs. Our results support the expectation that JH levels regulate female blood feeding behaviors. They also suggest that application of JHAs for larval control can unintentionally lead to additional blood feeding events per gonotrophic cycle, with potential increases in the transmission of disease agents.