Coumaphos is an organophosphate pesticide.1 It is converted into an oxon-containing metabolite in vivo, similar to other organophosphate pesticides, that inhibits acetylcholinesterase. It is active against adult, but not arrested stage, O. ostertagi helminths.2 Coumaphos is toxic to A. stephensi and A. aegypti mosquitoes when applied topically, with median lethal doses of 0.002 and 0.012 µg per female mosquito, respectively, but not when used as a contact insecticide.3 It is lethal to rats (LD50s = 41 and 16 mg/kg for male and female rats, respectively).4 Formulations containing coumaphos have been used to control pests in livestock.
1.Guo, J.-X., Wu, J.J.-Q., Wight, J.B., et al.Mechanistic insight into acetylcholinesterase inhibition and acute toxicity of organophosphorus compounds: A molecular modeling studyChem. Res. Toxicol.19(2)209-216(2006) 2.Prichard, R.K.Anthelmintics and controlVet. Parasitol.27(1-2)97-109(1988) 3.Hadaway, A.B., and Barlow, F.The toxicity of some organophosphorus compounds to adult Anopheles stephensiBull. World Health Organ.28(1)55-61(1963) 4.Gaines, T.B.Acute toxicity of pesticidesToxicol. Appl. Pharmacol.14(3)515-534(1969)