A survey of anthelmintic resistance on Belgian horse farms

A survey to determine the prevalence of anthelmintic resistance of cyathost omes was carried out on 13 horse farms distributed over five different Belg ian provinces. Based on faecal egg count reduction tests, resistance to meb endazole (a benzimidazole) was demonstrated on 12 (92%) of these 13 farms. The efficacy ranged from 0% to 100%. The efficacy of pyrantel could be eval uated on only three farms, where the faecal egg count reduction varied from 83% to 96%, which suggested a reduced efficacy of this drug on one farm. T he very high prevalence of mebendazole resistance in this study shows that drugs of the (pro-)benzimidazole family should not be used to control cyath ostome infections. This survey also demonstrates that the efficacy of anthe lmintics used for cyathostome control programmes on horse farms should be r outinely evaluated.