Pinworms in Horses

Signs of Pinworms in my Horse

Tail head itching is the most common sign reported when a horse has Pinworms.  The rubbing on fence post, feed tubs, mangers, and anything else that is convenient can be a sign of pinworms.   Other things can be a cause of itching, but when the itchiness is limited to the tail head and rear end it is most often an indication of Pinworms.  Pinworms can affect any age horses, however, may be seen more frequently in young horses.

It seems the number of Pinworms infections may be trending slightly upward.  Often times owners will report they found a worm hanging partially out of their horse’s rectum.  The female Pinworm does pass partially out of the rectum so she can lay her eggs around the exterior of the rectal ring, generally on the lower halve. The female passes all her eggs at one time and then she dies. The material she uses to glue the eggs to this area is about the consistence of egg whites. As it dries it causes the intense itching the horse feels in that area. One may also see these white, yellowish green, gray patches of eggs on the shin of the rectal ring if they lift the tail of their horse.

What are Pinworms?

(Oxyuris equi)

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Pinworms are the worms responsible for the statement often heard (my horse must have worms because it is rubbing it’s tail). The glue the adult female worm attaches her eggs to the exterior rectal tissue with is very irritating to the tissue. This irritation in the past has been a major cause of tail rubbing.

The patches contain many (several 100,000) microscopic eggs.  Since the eggs are laid outside the rectum they are not found in a normal fecal egg count.

However, due to the improvement in deworming medications and the cleanliness in most stables today the problems due to pinworms has been greatly reduced.

Therefore, when ordering your fecal egg count through our website, please mention that you think your horse may have Pinworms and we will include the items to collect a sample to test for Pinworms.  If we are running a fecal egg count on your horse, there is no extra charge for this special test.

To order a fecal egg count for your horse, Order Now

For additional questions please call us directly at (800) 544-0599 or email us at

Specimen Photos/Illustrations