Occasionally Important Parasites

Control of equine gastrointestinal helminths is traditionally focused on the 4 major parasite categories: cyathostomins,Parascaris equorum, Anoplocephala perfoliata and Strongylus vulgaris. While this is well justified by the pathogenicity and occurrence of these parasites, other helminth species may be of occasional importance in equine populations.

Oxyuris equi
The equine pinworm is very common, but is only rarely diagnosed because female worms do not shed eggs into the faeces, but rather in the perianal area within a proteinaceous fluid. As this fluid dries, it becomes irritating to the host, and the horse starts rubbing the perianal area. Pinworm eggs can only be occasionally found in routine egg counts, and examination of perianal scrapings or scotch tape imprints will be more successful procedures. Thus, the faecal egg count reduction test is not useful for evaluating treatment efficacy against O. equi. Over recent years, field veterinarians have raised increasing concern over apparent treatment failure of Oxyuris infections (Wolf et al. 2012; Reinemeyer 2012). Most often, these suspicions are based on persistence of tail-rubbing after anthelmintic treatment. However, tail rubbing can have numerous causes and such observations do not allow any conclusions regarding anthelmintic efficacy. [...]