Colon
Parasite: Encysted small strongyles (cyathostomes)
Parasite: Pinworms (Oxyuris equi)
Lifecycle:¹
Infective eggs are ingested on pasture and the larvae hatch in the small intestine. After further maturation they migrate to the cecum/colon of the horse. Adult female pinworms migrate up the rectum and out the anus to cement masses of eggs on the perineal area. The egg masses cause irritation, and environmental contamination occurs when horses rub the irritated area against posts and barn walls.
Clinical Signs:
Most common clinical sign is tail rubbing due to skin irritation in the perineal area.
Horses at greatest risk:
Young horses less than 18 months of age. Most horses develop immunity as they age.
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