Pinworms

The equine pinworm, Oxyuris equi, is more common in young horses but can infect horses of any age. Although larvae are known to cause inflammation in the large intestine, they do not usually cause clinical illness. The most common problem associated with pinworms is itching of the anus area caused by eggs deposited and adhering to the skin, which may progress to tail-rubbing.

  • Mature worms living in the horse’s gastrointestinal tract crawl out of the rectum and lay eggs on the skin around the horse’s tail.
  • Eggs enter the environment in feces or tail rubbing.
  • Eggs develop into larvae, which are consumed when the horse grazes.
  • Larvae become adults and migrate to various parts of the horse’s body.
  • Tail rubbing
  • Hair loss around tail
  • In severe cases, excoriation of the hindquarters or perineal skin
  • Age less than 3 years old
  • Contaminated pasture
  • Contaminated stalls or equipment (grooming supplies, tail wraps, fence posts, etc.)

Do not use in horses intended for human consumption.