Suicidal pinworms a leading cause of “itchy butt” syndrome in horses

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This episode is the grand finale of “The Parasite Journey of the Horse” series, with equine parasitologist Martin Nielsen taking a look at pinworms.

Pinworm in horses, or Oxyuris equi, is related to the pinworm that humans get but it is a different species.

Nielsen says the No.1 parasite that he gets questions about is the pinworm, with horse owners finding them in poop, taking a picture and asking about them. It’s one of the most common parasites in horses.

Female pinworms are fairly large, from 3 to 5cm long, and they stand out because they’re white and have a “needle” shape with a taper at one end. The males are rarely seen.

The infective stage of this parasite is its impregnated and infected eggs, which the horse ingests, and they hatch inside the intestine. The stay in the large intestine for the rest of their life, before the females take the long journey to the rear end of the horse, where they deliver their eggs out to the environment and die.

“So this is a suicide mission,” Nielsen says.

In the above picture, the female pinworm is protruding her rear end outside of the anus, and she is delivering a mass of eggs embedded in a gooey substance that sticks around the skin of the anus.
Here,  the female pinworm is protruding her rear end to deliver a mass of eggs embedded in a gooey substance that sticks around the skin of the anus.

In the above picture, the female pinworm is protruding her rear end outside of the anus, and she is delivering a mass of eggs embedded in a gooey yellow substance that sticks around the skin of the anus.

“Then she will die as she comes out. Then, the yellow substance dries and becomes flaky, and irritating and itchy.

“So you’ll see horses that having an itchy bum and rubbing their rear end against objects; we call it the tail rubbing. That’s the only manifestation of this parasite.”

This is the final episode in this popular series. Catch up with the earlier episodes (in order!):

Episode 1: Foal parasites
Episode 2: Ascarids, or roundworms
Episode 3: Small strongyles (cyathostomins)
Episode 4: Bloodworms
Episode 5: Tapeworms
Episode 6: Bots
Episode 7: Pinworms

See also: the inside secrets of “Creepy Crawlies”.

» For more from Dr Nielsen, check out his previous short video series on parasite control, starting here.

Martin K Nielsen

Dr Martin Nielsen is an assistant professor in equine parasitology at the Maxwell H. Gluck Equine Research Center at the University of Kentucky. » Read Martin's profile

One thought on “Suicidal pinworms a leading cause of “itchy butt” syndrome in horses

  • June 11, 2020 at 10:30 pm
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    Is there a cleaning agent or solvent which would work to remove and/or neutralize the egg masses that are deposited near the rectum without harming the horses skin? Is there a protocol like daily wiping or cleaning of the skin and hair area near the rectum that could help prevent the itch?

    Reply

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