Peer-reviewed veterinary case report
Moxidectin works faster than fenbendazole for horse strongyle eggs
By Rossano, M G et al.·Published in Veterinary parasitology·2010·Department of Animal and Food Sciences, United States·View original on PubMed →
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Original publication title: Shortened strongyle-type egg reappearance periods in naturally infected horses treated with moxidectin and failure of a larvicidal dose of fenbendazole to reduce fecal egg counts.
- Species:
- horse
Plain-English summary
A group of 15 yearling horses were treated for strongyle-type worm infections, with some receiving a five-day course of fenbendazole and all receiving a single dose of moxidectin later on. The fenbendazole treatment did not significantly lower the number of worm eggs in their feces, while moxidectin was effective in reducing egg counts to zero for 21 days. However, by day 42, most horses had some eggs present again, indicating that the effectiveness of moxidectin may decrease over time. This suggests that fenbendazole may not be a reliable option for controlling these parasites in horses.
People also search for: horse deworming moxidectin · fenbendazole for strongyles in horses · horse worm egg counts
Abstract
Deworming horses with anthelmintics that have activity against encysted small strongyle larvae (L(3) and L(4)) is a common practice in parasite control programs. The two drugs currently available for this use are moxidectin (MOX) administered in a single dose of 0.4 mg/kg and fenbendazole (FBZ) given at the larvicidal dose (10mg/kg for 5 days). Here, we report the efficacy of MOX and the larvicidal dose of FBZ for reducing counts of strongyle-type eggs per gram of feces in naturally infected horses. Fecal egg counts (FECs) of 15 yearlings were observed following deworming. On day 0, 6 of the 15 yearlings were administered a larvicidal dose of FBZ; 14 days later, all 15 yearlings received MOX at a single dose of 0.4 mg/kg. Feces were collected on day 0 for pre-treatment egg counts. Feces were collected at weekly intervals thereafter during FEC observation periods. FECs of FBZ-treated horses were compared at day 0 and 14 days post-treatment. The difference in means pre- and post-treatment with FBZ was not statistically significant (p=0.65). On days 0 and 42 of the MOX treatment observation period the mean FEC of the yearlings that had not received the FBZ treatment did not differ significantly from that of the FBZ-treated yearlings. MOX was effective in reducing fecal egg counts to 0 EPG for 21 days. At day 35 all but 2 of the yearlings had some eggs present (range=4-361 EPG) and at day 42 all but 1 yearling had eggs present (range=3-432 EPG). At day 42 the group mean FEC reduction had fallen from 100% to 67%. Results of this study do not support the use of the larvicidal dose of FBZ for small strongyle control. Larger field studies will be needed to investigate whether egg reappearance periods are shortening for MOX-treated horses.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/20675055/