Efficacy of avermectin B1 given orally against equine intestinal strongyles and Onchocera microfilaria.

This research paper investigates the effect of the drug avermectin B1, when administered orally, on the presence of intestinal strongyles and Onchocera microfilaria in horses and ponies. The study finds that avermectin B1 is highly effective at reducing these parasites, although its effectiveness is less prolonged compared to a comparable drug, ivermectin.

Research Methodology

• The study included three groups of horses and ponies of varying sizes, with 13 in two groups and 12 in another group. These animals were treated with 0.2mg/kg of ivermectin paste orally, 0.2mg/kg of avermectin B1 solution orally, or 10 mg/kg of a fenbendazole suspension via a nasogastric tube.
• The avermectin B1 was a 1% solution based in propylene glycolglycerol formal.
• The level of strongyle (a type of intestinal worm) eggs in the faeces of the horses were counted before treatment, and then subsequently at 14-day intervals up to 70 days after treatment.
• In addition, full-thickness skin biopsies were taken from the neck, chest and belly button areas of the horses to check for Onchocera microfilaria (a type of parasite) before treatment and again 14 and 70 days later.

Research Findings

• The study finds that treatment with ivermectin resulted in a significant decrease in the mean strongyle egg counts 14, 28, 42 and 56 days after treatment.
• Avermectin B1 therapy also resulted in significant decreases in mean strongyle egg counts 14, 28 and 42 days after treatment, indicating that it too is effective at reducing this parasite.
• All horses given avermectin B1 or ivermectin had no strongyle egg counts 14 and 28 days after treatment, demonstrating the effectiveness of these drugs.
• On the other hand, treatment with the fenbendazole suspension did not significantly decrease strongyle egg counts.
• Both ivermectin and avermectin B1 resulted in zero microfilaria counts in all horses 14 days after treatment, indicating their effectiveness against this parasite as well. On day 70, the decrease in microfilaria counts were 100% and 99.6% respectively.
• The fenbendazole suspension did not significantly decrease microfilaria counts.

Research Conclusion

• This study concludes that the oral administration of the avermectin B1 formulation appears to be highly effective against intestinal strongyles and Onchocera microfilaria.
• However, the duration of the anti-strongyle activity of avermectin B1 is significantly shorter than that of ivermectin paste.