Helminths in horses: use of selective treatment for the control of strongyles.

The research article examines the effectiveness of selective treatment for controlling strongyles in horses, with an emphasis on reducing the use of anthelmintics. The findings suggest that this approach can help manage anthelmintic resistance, minimizing helminth burdens while lessening the frequency of treatments.

Research Objectives and Approach

The study focused on several key objectives:

• To ascertain whether the pattern of egg excretion from strongyles varied across different age groups of Thoroughbred horses in the Western Cape Province (WCP).
• To determine if selective treatment can lessen the need for anthelmintic treatments while maintaining minimal helminth burdens in adult Thoroughbred horses.
• To assess the efficacy of subsampling large horse herds for faecal egg counts (FECs) in monitoring strongyle burdens.

To achieve these goals, faecal samples were collected and analysed from different horse groups in the WCP in 2001, including adult mares, yearlings and weanlings from various farms. In 2002/2003, faecal samples were taken every 3-4 weeks from 52 adult Thoroughbred mares from one particular farm in WCP.

Findings and Implications

The study observed that:

• There were generally fewer egg-excreting individuals with lower average FECs amongst the mare herds compared to the younger age groups.
• Horses with strongyle FEC > or =100 eggs per gram (epg) were treated with a combination of ivermectin-praziquantel (Equimax oral paste, Virbac). This resulted in the mean monthly strongyle FEC for the entire group remaining <300 epg throughout the study, while the number of treatments was slashed by 50%.
• Resampling methods revealed that an asymptote to mean FEC was reached at 55 animals for each of the pooled weanling, yearling and mare egg counts. Furthermore, resampling within four different mare herds recorded asymptotes of between 24 and 28 animals.

These findings suggest that subsampling large horse herds for FECs is an effective approach for treatment management.

In conclusion, the study provides evidence that selective treatment is both practical and effectual in the management of anthelmintic resistance. This could have significant implications for the horse-breeding industry where high levels of anthelmintic resistance is a current problem.