Selective treatment of strongylosis in horses: results of two years of monitoring

Abstract

The purpose of the research is to evaluate the applicability and efficiency of selective anthelmintic therapy for strongylosis of the digestive tract in horses based on two years of monitoring at a single equestrian farm using the “top 20%” selection principle based on the number of helminth eggs. Materials and methods. A longitudinal observational study was conducted on 32 horses over a period of 24 months. Quantitative ovoscopy was performed at approximately 4-month intervals to determine the average number of strongyle eggs per 1 g of faeces. The top 20% of animals in terms of EPG in each cycle (taking into account equal values at the border) were included in deworming with ivermectin (0,2 mg/kg). We assessed the dynamics of EPG, the contribution of the target group to the total number of eggs excreted, the extensive efficiency (%) on the 14th day after treatment, and the statistical significance of the changes (Friedman's criterion, Wilcoxon's criterion, bootstrap analysis). Results and discussion. The distribution of EPG was distinctly aggregated: about 20% of horses consistently formed an average of 50,3% (95% CI: 47,1–57,2%) of the total number of strongylid eggs excreted by all animals (Р < 0,05). The median EPG decreased from 82,5 to 28 eggs/g during the observation period (Р < 0,05). The extensive efficiency of ivermectin was 100% (95% CI: 91,6–100%) in all 42 cases of deworming. The use of a selective scheme reduced the number of treatments by 78,1% compared to traditional mass deworming, while maintaining a low parasite load. The data obtained confirm the epizootological and economic feasibility of selective therapy in stabled and pastured farms, provided that the EPG index is regularly monitored, and can serve as a basis for the development of adapted protocols for the control of strongylosis in horses.