The toxicological effects and bioaccumulation of fipronil in larvae of the mosquito Aedes aegypti in aqueous medium

Abstract The toxicity and bioaccumulation kinetics of fipronil were analyzed on fourth instar larvae of an Aedes aegypti laboratory strain in order to investigate the possible use of this new phenylpyrazole insecticide in the aquatic medium. Standard bioassays indicate that larvae fed with maize flour on which the fipronil has accumulated are about three times more susceptible to fipronil than unfed larvae because fed larvae ingest considerably more fipronil than unfed larvae. Bioaccumulation kinetic analysis, comparatively performed in simplified experimental microcosms, using [ 14 C]fipronil solutions against dead larvae and living unfed larvae treated or not by Triton X-100, suggests that the insecticide penetrates mainly through the integument but also through the gut. This digestive route of fipronil accumulation is enhanced by feeding, suggesting that ingestion be the main and most selective way of insecticide administration to mosquito larvae. These biological effects of fipronil may offer a possible strategy of use of this insecticide in larval mosquito control.