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


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.

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

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.