In-feed antiparasitic veterinary drug emamectin benzoate impairs acetylcholinesterase activity and brain tissue histoarchitecture of Oreochromis niloticus fry

•The neurological responses of dietary emamectin benzoate (EB) in tropical fish are limited.•EB-dosed O. niloticus recorded a dose-dependent reduction in acetylcholinesterase.•Histologically, dose-dependent alterations in the brain tissues were documented.•The observed alterations were mild and reversible upon the termination of dosing.