Efficacy of fenbendazole in small ruminants on Southern New England farms

Abstract

Parasite control is a major challenge and contributor to economic loss and animal illness in the small ruminant industry. Given the burden of parasitism and lack of anthelmintic resistance surveillance, the purpose of this study was to determine the clinical efficacy of fenbendazole in sheep and goats in Southern New England in the United States. Thirty sheep and eighty goats from nineteen farms in Connecticut, Massachusetts, and Rhode Island were sampled for fecal egg counts (FEC) pre- and post-administration of a 10 mg/kg oral dose of fenbendazole (Panacur® 10 % oral suspension). This study found an average fecal egg count reduction (FECR) of 41 % (90 % CI [0, 0.45], p < 0.05), with 87.3 % (96/110) of animals failing to meet the minimum clinically recommended threshold of 90 % for FECR. Of the individual animals that exhibited a failure of treatment, 35 % (34/96) had an increased FEC after treatment. Reduced efficacy of fenbendazole against strongyle-type gastrointestinal nematodes (GIN) in small ruminants was observed on all nineteen farms. Farms without animal movement off and back onto the property had a median FECR of 54.2 %, and farms that had movement had a median FECR of 25 %, but this was not statistically significant. Seasonal timing of FEC tests are important for accurate detection and appropriate treatment. A two-sample t-test confirmed that two groups, divided by a date of June 12, have a significantly different average initial FEC. This study emphasizes the unreliability of fenbendazole efficacy in these populations and the necessity of monitoring FECs alongside on-farm management tools.