Skip Ribbon Commands Skip to main content
Share This

Endoparasites - Oxyuris

Oxyuris equi: Equine pinworm

General Description: The male pinworm is 9 to 12 mm. long. The female, up to 150 mm. in length, has a characteristically long, pin-like tail with a much larger body.

Life Cycle: Adult female worms migrate out of the anus and lay eggs on the perianal skin. The eggs are covered with sticky fluid. Depending on temperature, the eggs embryonate and become infective in 3 to 5 days. The horse may increase its infection by biting at the larvae in the itchy fluid. Otherwise, eggs may drop into feed and water. The ingested larvae penetrate the lining of the large intestine, where they feed on the mucosa. Maturity is reached in 4 to 5 months.

Location: Large intestine, anus.

Geographical Distribution: Common throughout the world.

Significance: Importance is mainly limited to aesthetic considerations. Chronically infected horses have a very poor appearance. Heavy infections also cause severe irritability.

Effect on Host: Some ulceration can result from the mucosal feeding of the larvae. Most of the clinical significance results from the intense itching caused by the sticky fluid with which Oxyuris eggs are attached to the rump. In addition to loss of condition and poor appearance, biting and scratching may cause wounds open to infection. Severe cases can lead to nervousness and anorexia. Rubbing and scratching at the perianal region cause irritation, dull hair coat, and loss of hair known as "rat-tail."

Diagnostic Information: Presence of masses of whitish- yellow eggs around the anal region. Eggs are collected using transparent adhesive tape.

Control: Cleanliness and frequent changes of bedding will restrict reinfection. Treatment will eliminate intestinal worms.

Oxyuris– egg   Rat-tail appearance of host



Back to Horse Disease Information