Pinworm infection

Veterinary advice should be sought before applying any treatment or vaccine.

Pinworm Infection

Pinworms (Oxyuris equi) are one of the primarily causes of tail rubbing in horses. Through rubbing, horses spread the eggs of the pinworm throughout their environment, which are able to live for a significant period of time since they are quite hardy.

How Pinworms are Transmitted to Horses

Horses become infested with pinworms from ingesting their eggs from contaminated pasture grass, fence posts, feed, hay, water, stalls, or anywhere close to where infected horse was rubbing their tail. Once ingested, pinworm eggs hatch and larvae mature in the large intestine, while feeding off the intestinal lining until they mature into adults. Once mature adults, pinworms relocate to the anus where they lay their eggs, that they cover with a sticky fluid that causes severe itching.


Tail rubbing
Intense itching
Loss of hair


  • History
  • Clinical signs
  • Physical exam
  • Fecal exam



Deworming through the implementation of a barn-wide program. See Recommended Deworming Schedule


  • Rotate pastures, if possible
  • Remove manure from pastures and paddocks
  • Avoid overstocking pastures
  • Harrow pastures only during hot, dry periods and keep horses off for several weeks
  • Rotate cattle, sheep or goats into pastures previously occupied by horses, since the larvae becomes inactivated by consumed by other species.
  • Compost manure
  • Feed horses in buckets as opposed to off the ground.
  • Group pastures according to age to reduce exposure to younger horses.

Scientific Research

General Overviews

Age Range

Horses between the ages of 1–4 years are more likely to harbor larger worm burdens, and have higher egg counts than adult horses.