Equine Gastrointestinal Parasites Study Guide

Overview and Clinical Importance

Gastrointestinal parasitism represents one of the most significant health challenges in equine practice worldwide. Understanding the biology, pathogenesis, diagnosis, and treatment of these parasites is essential for NAVLE success and clinical competency. The major equine GI parasites include cyathostomins (small strongyles), Strongylus vulgaris (large strongyles), Parascaris equorum (ascarids), Anoplocephala perfoliata (tapeworms), and Oxyuris equi (pinworms).

The emergence of widespread anthelmintic resistance has revolutionized parasite control strategies, shifting from interval-based deworming to evidence-based targeted treatment programs using fecal egg counts (FEC) and fecal egg count reduction tests (FECRT).

Cyathostomins (Small Strongyles)

Cyathostomins are currently considered the most prevalent and clinically significant internal parasites of horses worldwide. Over 50 species exist within 14 genera, with approximately 40 species capable of infecting horses. Prevalence rates exceed 90% in grazing horse populations regardless of climate or management.