Metabolism of Coumaphos in Larvae of the Cattle Tick Boophilus Microplus

Abstract

[p32]Coumaphos, a phosphoro-thionate, was rapidly absorbed and metabolized by cattle tick larvae dipped in aqueous suspensions of the acaricide. One metabolite was shown by chromatographic, spectroscopic, and cholinesterase inhibition evidence to be the oxygen analogue, a more potent in vitro cholinesterase inhibitor than the parent compound. Other water-soluble metabolites were only tentatively identified. Sublethal doses were metabolized mainly to water-soluble materials and a small quantity of oxygen analogue whereas lethal doses, producing complete mortality in 2-3 hr, yielded almost equal amounts of the oxygen analogue and water-soluble materials. In vivo inhibition of cholinesterase in treated larvae was dose-dependent and preceded death.