Prevalence of fenbendazole resistance in ovine nematodes in north west India.

A survey was undertaken between March and September 1992 to assess the prevalence of fenbendazole resistance in sheep nematodes in 32 traditionally managed rural flocks and 22 intensively managed flocks on 3 farms. Fenbendazole, a commonly used anthelmintic was used at the recommended dose of 5 mg/kg body weight. Efficacy was determined on the basis of percentage reduction in strongyle faecal egg counts (FECR%) and larval cultures before and between 7 and 10 days after treatment. None of the traditionally managed rural flocks showed resistance and all had greater than 99% reduction in faecal egg counts after treatment. Of the 22 intensively managed flocks, however, 15 had slight fenbendazole resistance (between 60 and 90% reduction in egg counts) and 4 had severe resistance (less than 60% reduction).