Not playing by the rules: Unusual patterns in the epidemiology of parasites in a natural population of feral horses () on Sable Island, Canada.

Sable Island, Nova Scotia, Canada hosts one of few natural populations of feral horses () never exposed to anthelmintics. Coproculture revealed cyathostomes, and , with (unusually) dominating in adult horses and cyathostomes dominating in young horses (<3 years of age). We examined 35 horses found dead in the springs of 2017 and 2018, as well as fecal samples from live horses in spring (n = 45) and summer 2018 (n = 236) using McMaster fecal flotation and Baermann larval sedimentation on fresh samples, and modified Wisconsin flotation and sucrose gradient immunofluorescent assay for and on frozen samples.