Intestines

Parasite: Encysted small strongyles (cyathostomes)
#1 Parasite Concern for Adult Horses

Lifecycle:¹

Adult worms are found in the cecum and colon of infected horses. The adults lay eggs which are passed in the feces. Eggs hatch and the larvae mature to the infective L3 stage. Third stage larvae are ingested on pasture and invade the mucosa of the large intestine. At this time the larvae may hibernate – or encyst – for prolonged periods of time. As many as 90% of the larvae may become encysted in this manner2 and remain in this stage of development for 4 months or up to 2 years3. The climate dictates when hibernation occurs and when the larvae will emerge and continue toward maturation.

Clinical Signs:

Primary disease threat lies in mass emergence from the encysted stage, which can lead to weight loss, diarrhea, colic, edema, fever, dull hair coat, decreased performance and even death.

Horses at greatest risk:

Considered a major parasite risk in adult horses. Young horses and immunocompromised horses are also susceptible.

REFERENCES

1. Handbook of Equine Parasite Control, Second Edition. Martin K. Nielsen and Craig R. Reinemeyer. © 2018 John Wiley & Sons, Inc. Published 2018 by John Wiley & Sons, Inc
2. Proudman CJ, Matthews JB. Control of Intestinal Parasites in Horses. In Practice. 2000; 22:90-97.
3. Corning, S. Equine cyathostomins: a review of biology, clinical significance and therapy. Parasites & Vectors 2009, 2(Suppl 2):S1 doi:10.1186/1756-3305-2-S2-S1