Pinworms usually are the cause of the irritation that leads to tail rubbing. | Photo: iStock

Q: My horse is constantly rubbing his tail on anything he can find. It has become so bad that the hair at the base of his tail has either fallen out or become matted. Thankfully, I’ve finished my show season, but what is causing him to do this? He also seems to be losing weight. Are these two problems related?

A: Tail rubbing, commonly known as rat tail, broken hair, or matted tail, most often can be a symptom of pin worm infestation. Tail rubbing is a condition resulting from the horse’s rubbing back and forth on an object–such as a fence post, feed buckets, or water buckets–in order to relieve the itching, or pruritis, which might be caused by the eggs of pinworms that are laid around a horse’s anal area. The horse literally can take the hair off its tail by the amount of rubbing it does.

The guilty culprit in some cases of tail rubbing is the pinworm (Oxyuris equi); this is not always the case. Other reasons horses rub the hair off their tails include the following: insect hypersensitivity, food allergy, pediculosis (lice infestation), mange, or in rare cases a behavioral vice much like cribbing