Diarrhea Associated with Parasites

Australian researchers published a review article about "Diarrhea associated with gastrointestinal parasites in grazing sheep." Diarrhea is a common and widespread problem in sheep. In many places, it is a major risk factor for flystrike.

Gastrointestinal parasites have long been recognized as a cause of diarrhea in sheep. Of the worm species affecting sheep, Trichostrongylus spp. and Teladorsagia are most commonly associated with diarrhea. In young sheep, Nematodirus spp. may be associated with diarrhea. Haemonchus contortus does not cause diarrhea.

Diarrhea associated with large worm burdens is managed through integrated parasite management programs that combine chemical and non-chemical methods of parasite control. Despite limitations, fecal egg count is the mainstay for assessing the contribution of worms to outbreaks of diarrhea.

In some geographic locations, "larval hypersensitivity diarrhea" is emerging as a significant cause of worm-related diarrhea, but in sheep without large worm burdens. This heightened inflammatory response is best addressed though selecting sheep for low breech soiling (dag scores), as worm resistant sheep (low FEC) have in increased propensity for diarrhea.

Diarrhea in young sheep is more complex. It is usually multifactoral. Concurrent infections with worms and protozoan parasites (e.g. coccidia) are common. Determining the contribution of protozoan parasites to clinical disease in diarrhea outbreaks can be challenging.

Source: Veterinary Parasitology June 2020. Read abstract