Anthelmintic efficacy in strongyles of horses in Northern Minas Gerais, Brazil.

This study assesses the efficiency of three deworming drugs, fenbendazole, ivermectin, and abamectin, in handling parasitic infection in horses across 24 farms in Northern Minas Gerais, Brazil.

About the Study

• This study was conducted on 24 horse farms in Northern Minas Gerais, Brazil and involved 619 animals. Due to the increasing concern about parasite resistance to deworming drugs, the researchers aimed to evaluate the efficacies of three common equine deworming drugs – fenbendazole, ivermectin, and abamectin.

Methodology

• In order to assess the resistance of parasites to these drugs, the researchers initially performed egg counts per gram of feces (EPG) individually for each horse. This step determined the extent of parasitic infection in the animal.
• Only animals with significant levels of infection (EPG counts of 150 or more) were used for the main part of the trial. This amounted to a total of 436 animals.
• These horses were then divided into groups and treated with one of the three anthelmintics.
• Two weeks after the administration of the anthelmintics, feces were collected again from the horses and the EPG count was repeated.
• The reduction in EPG count after treatment (faecal egg count reduction, FECR) was then calculated for each anthelmintic group. This served as an indicator of the drug’s effectiveness.

Findings

• The results showed that fenbendazole was effective in about 46% of the tested farms. Ivermectin and abamectin were more effective, working in about 77% and 74% of the farms respectively.
• However, parasite resistance to deworming drugs was observed in over 58% of the farms. This indicates a significant challenge for equine health in the region.
• Among the parasites identified, Cyathostomin larvae were found in all the farms. Strongylus vulgaris was present in more than half of the farms, and S. equinus in around 13% of the farms. Cyathostomins were the only type of larvae detected post-treatment with ivermectin and abamectin.

Conclusion

• The intensive use of anthelmintics may be raising resistance levels in parasite populations. As the drugs become less effective, it is important to explore alternative strategies to maintain equine health.