Comparison of the cyathostomin egg reappearance times for ivermectin, moxidectin and abamectin in horses in consecutive egg count reduction tests in winter and summer over two years

Abstract

Shortened cyathostomin egg reappearance periods (ERP) serve as a warning of developing anthelmintic resistance (Scott et al., 2015). Efficacy is thought to have declined more rapidly for the later larval stages (L4) than for the egg laying adults, so that animals still show zero or near zero counts for a period after treatment, but with L4 now surviving treatment the ERP has shortened.