Changes in the acetylcholinesterase activity of the nematode Nippostrongylus brasiliensis following treatment with benzimidazoles in vivo

Acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) activities of Nippostrongylus brasiliensis were measured following treatment of the hosts with oxfendazole and mebendazole. Drug treatment of N. brasiliensis caused large, sustained increases in enzyme activity in male and female worms which coincided with the expulsion of the nematodes from the small intestine of the host. It is suggested that the increases in acetylcholinesterase activity may be due to an inhibition by the benzimidazole carbamates of the secretion of enzyme to the exterior of the worms which, in turn, leads to expulsion through failure of the so-called ‘chemical holdfast’.