Cyathostome fecal egg count trends in horses treated with moxidectin, ivermectin or fenbendazole.

Commercial preparations of fenbendazole (Safe-Guard, Intervet), ivermectin (Eqvalan, Merial) or moxidectin (Quest, Fort Dodge) were administered once to horses scheduled for routine parasiticide treatment. In total, 93 horses from six cooperating farms were used in the study. Computer generated, random allocation of horses to treatment group was conducted at each farm. Fecal egg counts were determined for all horses on trial days 0, 56, 84 and 112, with corresponding calendar dates that were unique to each farm. Only strongyle egg counts from animals which were positive at day 0 were used for analysis of variance and comparisons. Counts for the three treatment groups were similar at day 0, moxidectin<ivermectin<fenbendazole for days 56 and 84, and moxidectin<ivermectin=fenbendazole on day 112 (P<0.05). Reductions of geometric mean egg counts from day 0 levels were 99.1, 97.6 and 94.9% for moxidectin, 16.4, -27.0 and -32.0% for fenbendazole and 85.9, 24.2 and -8.1% for ivermectin on trial days 56, 84 and 112, respectively. Adverse reactions to treatment were not observed for any of the parasiticides.