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

This study evaluates the effectiveness of three commercially available anthelmintics (moxidectin, ivermectin, and fenbendazole) in reducing horse worm egg counts over specific periods of time. The trial finds moxidectin most effective, followed by ivermectin, and fenbendazole.

Methodology

• The experiment involved 93 horses from six different farms, which were all due for routine parasite treatment. The selection of horses for the treatment groups was randomized.
• Fecal egg counts for all participating horses were recorded on trial days 0, 56, 84, and 112. The specific calendar dates varied for each farm.
• The data used for the analysis and comparison consisted only of strongyle egg counts from horses that tested positive on day 0.

Results

• The three treatment groups had comparable strongyle egg counts at the beginning of the study.
• By days 56 and 84, moxidectin proved to be the most effective treatment, followed by ivermectin, while fenbendazole was the least effective (moxidectin<ivermectin<fenbendazole).
• On day 112, moxidectin remained the most potent option, with ivermectin and fenbendazole showing similar efficacy (moxidectin<ivermectin=fenbendazole).
• In terms of the percentage reduction in geometric mean egg counts from day 0 levels, moxidectin led the pack with 99.1% on day 56, 97.6% on day 84, and 94.9% on day 112. Ivermectin, while not as effective as moxidectin, outperformed fenbendazole registering reductions of 85.9% on day 56, 24.2% on day 84, and a slight increase of -8.1% on day 112. Fenbendazole was the least effective treatment, with negative reduction percentages of -27.0% on day 84 and -32.0% on day 112, indicating an increase in egg counts.
• No adverse reactions were observed with any of the treatments.

Conclusion

• The study evidences that while all three treatments can reduce parasite counts in horses, moxidectin is the most effective. It does, however, underscore that the choice of treatment may need to account for the time since last deworming as effectiveness of ivermectin and fenbendazole noticeably reduced over the trial period.
• Another critical takeaway is that none of the treatments caused any adverse reactions, suggesting that they are all safe for use in parasite management among horses.