Estimating the Prevalence and Factors Affecting the Shedding of Helminth Eggs in Irish Equine Populations

Gastrointestinal helminths are ubiquitous in horse populations across the world. Intensive anthelmintic treatments have succeeded in controlling some of the pathogenic effects of these parasites. However, the success of anthelmintic drugs has been threatened by the development of widespread resistance to those most commonly used. To develop improved control strategies, information on helminth distribution patterns is needed, which can be obtained by identifying animals regarded as high egg shedders and taking age, gender, and other risk factors into account. The aim of this study was to determine the prevalence of helminth infection in the Irish equine population using faecal egg counts and to evaluate the effects of risk factors on these faecal egg counts. For the 2700 horses that were included in the study, the prevalence of gastrointestinal helminth infection was 52.40%, 4.22%, 2.59%, and 0.89% for strongyle species, Parascaris spp., Anoplocephala spp., and Strongyloides westeri, respectively. Overall, strongyle faecal egg counts from 159 farms averaged 250.22 eggs per gram. Both age and season had significant effects on strongyle egg shedding. In conclusion, this study revealed high prevalence of strongyle worm infection in horses on Irish farms, which highlights the need to optimize and develop good management practices and strategic deworming.