Selective anthelmintic therapy of horses in the Federal states of Bavaria (Germany) and Salzburg (Austria): an investigation into strongyle egg shedding consistency.

This study explores the use of selective anthelmintic treatment for horses in the areas of Bavaria, Germany and Salzburg, Austria. The research found this method, which involves only treating horses when strongyle egg counts exceed a certain threshold, to result in reduced overall use of anthelmintic treatments and an associated decrease in strongyle egg pasture contamination.

Research Methodology

• Over the course of nine months (from March to November 2008), 129 horses within 40 km of Salzburg, Austria had faecal samples collected each month.
• These samples went through a quantitative analysis using a modified McMaster egg counting technique.
• If a faecal egg count (FEC) result exceeded 250 eggs per gram (EPG), the horse received treatment with either pyrantel, ivermectin, or moxidectin.

Key Findings

• Out of 129 horses, no strongyle eggs were detected in 52 horses (40.3%) over the nine-month duration.
• In 39 horses (30.2%), strongyle eggs surfaced in at least one sample, but the egg count never exceeded 250 EPG.
• The remaining 38 horses (29.5%) received at least one treatment in response to a FEC that crossed 250 EPG.
• Through this selective anthelmintic scheme, the total number of anthelmintic treatments significantly reduced to 54% of that administered to the same horses in the preceding year.
• Both the maximum and mean FEC considerably reduced post the onset of this study.
• A significant negative correlation was demonstrated between a horse’s maximum and mean FEC and its age.
• Despite observing a decrease in FEC with better pasture hygiene, the effect was not statistically significant.

Implications of the Study

• The initial FEC of a horse was found to be significantly correlated with the maximum FECs in the subsequent eight months, suggesting that higher initial FEC may be predictive of higher subsequent FECs.
• Horses which necessitated multiple anthelmintic treatments had a higher initial FEC and a greater maximum FEC in the first two samples compared to horses which required only one or no treatment.
• This research underscores that selective anthelmintic treatment can lead to reduced pasture contamination with strongyle eggs, while also decreasing the number of utilized anthelmintic treatments.
• Persistent implementation of a selective treatment strategy could potentially lower the selection pressure for anthelmintic resistance.
• The study’s findings provide valuable insights to aid equine practitioners in conceptualizing and overseeing sustainable anthelmintic treatment programs.