Field efficacy of ivermectin, fenbendazole and pyrantel embonate paste anthelmintics in horses.

This research compares the efficacy of three deworming treatments (ivermectin, fenbendazole, and pyrantel embonate) in reducing parasite egg counts in horse feces, showing that ivermectin offers the longest duration of suppression.

Research Context

• The main aim of the research was to compare the effectiveness of three antiparasitic pastes: ivermectin, fenbendazole, and pyrantel embonate in horses.
• The study tested their ability to suppress the output of parasite eggs in horse feces over time after a single treatment.
• The samples were collected from 108 horses across four grazing sites in Britain during the summers of 1985 and 1986.

Research Method and Findings

• Each of the horses was treated with either ivermectin, fenbendazole, or pyrantel embonate. Their feces were then observed for the reappearance of parasite eggs.
• The median period before parasite eggs reappeared was 70 days for the ivermectin group, 14 days for the fenbendazole group, and 39 days for the pyrantel embonate group.
• Geometric mean faecal egg counts in the groups treated with ivermectin and pyrantel embonate were significantly less (P less than 0.05) than in the fenbendazole group after 21, 28, 35, and 42 days from the treatment. After days 49, 56, 63, and 70, the egg counts in the ivermectin group were even significantly lower (P less than 0.05) from those in the other groups.

Implications of the Study

• The results show that ivermectin treatment is the most effective among the three in suppressing the output of parasite eggs, halting their appearance in feces for a longer duration.
• According to this research, to achieve minimum pasture contamination, a second treatment would have been necessary 10 weeks after the first treatment for horses treated with ivermectin.
• For fenbendazole or pyrantel embonate treatments, second treatments would be required after approximately two weeks and six weeks respectively.
• The findings have implications for effective horse deworming and pasture management, suggesting ivermectin paste yields longer periods of effectiveness in preventing pasture contamination compared to the other tested treatments.