Anthelmintic resistance of horse strongyle nematodes to fenbendazole in Lithuania

Abstract

Background: with intensive use of anthelmintic drugs in recent decades, anthelmintic resistance (AR) in horse nematodes is becoming a growing issue in many countries. However, there is little available information about the parasites, treatment practices or AR in the horse population in Lithuania. The aim of this study was to assess the current situation of fenbendazole AR on horse farms in Lithuania. Results: the study was conducted in six stables and only the horses with a strongyle faecal egg count (FEC) of ≥ 200 eggs per gram were selected. One hundred and twenty-one faecal samples were examined with McMaster technique Faecal egg count reduction tests (FECRT) were performed on the 89 horses that met the inclusion criteria. Resistance to fenbendazole (FBZ) was found in three stables (50% of all tested herds). The FEC showed a significant (P<0.01) difference between the treatment and control groups. Only cyathostomin larvae were detected in larval cultures derived from strongyle-positive faecal samples collected 14 days after treatment of a test group with FBZ. Conclusions: this in vivo study showed that resistance to FBZ is prevalent on horse farms in Lithuania. These findings should guide the implementation of more sustainable management of strongyle infections in horses in Lithuania.