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What is Oxyuris sp ?

Oxyuris sp is a common condition in horses.  The parasite oxyuris equi does not travel to other organs of the body, it remains in your equine’s large intestine. Therefore, it causes little internal physical damage to the horse. 

The worms are gray in color. The female oxyuris equi can grow up to 10cm in length.  The male worm is much smaller; it is usually less than 1 cm in length. Oxyuris equi feeds on the mucosal lining of your horse’s intestine.

The adult female oxyuris sp gravitates towards the horse’s rectum and produces a yellow, sticky substance around the anus in which to lay her eggs. The crusty yellow mass containing the larvae can cause severe irritation to the horse’s perianal area. The horse’s constant scratching can lead to abrasions and lesions, which may become infected. Oxyuris sp is not life threatening but it is an extremely bothersome condition to the horse. If your horse is excessively scratching at his hindquarters, he needs to be seen by a veterinarian.

Oxyuris sp in horses is an infestation of the intestinal parasite oxyuris equi.  Oxyuris sp in horses is also known as pinworm, equine worm and rat-tail.

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Symptoms of Oxyuris sp in Horses

Symptoms may include:

  • Skin irritation around the anus
  • Biting and licking of the hindquarters
  • Hair loss patches
  • Red inflamed skin 
  • Abrasions or lesions on the hindquarters
  • Tail appears ungroomed; “rat-tailed” appearance
  • Rubbing tail against stall walls, scratching posts and trees
  • Visually seeing the worm on the horse’s anus
  • White/yellow crusty substance around the anus (pinworm eggs)
  • Horse is restless and irritable 
  • Lack of appetite
  • Weight loss
  • Dull coat

Causes of Oxyuris sp in Horses

The ingestion of the parasite oxyuris equi larvae causes oxyuris sp in horses.  The larvae can be transmitted by: 

  • The horse ingests the larvae from a contaminated pasture
  • Close contact (mutual grooming) with an infected horse
  • The horse drinks water which contains the parasite
  • Oxyuris equi larvae is transferred and ingested from infected scratching posts, stables, padlocks, trailers or fence posts
  • Feeding the horse on the ground, which may have parasites
  • Sharing of contaminated grooming or tack equipment

Diagnosis of Oxyuris sp in Horses

The deworming records of your horse must be available for the veterinarian to evaluate. If parasites are suspected the veterinarian will take a scraping of the perianal area.  The scraping will be put on a slide and examined under a microscope. Sometimes clear tape is used instead of a scraping.  The tape is placed around the horse’s anus and then pulled off.  The adult pinworm and specimens of the eggs will be caught on the tape. A complete blood count may be recommended to determine if there is a bacterial infection or if the patient is anemic.

Treatment of Oxyuris sp in Horses

If the veterinarian diagnosed the patient with oxyuris sp he will recommend an oral dewormer. Pyrantel and ivermectin paste are common dewormers used to eliminate pinworms. The veterinarian may suggest that other horses that share the paddocks and pasture should be dewormed as a preventative. 

The horse’s anus and perianal area will need to be thoroughly cleaned.  The patient’s caregiver should wear gloves so not to transmit pinworms to other horses. The veterinarian may suggest an enema to help flush out the parasites from the rectum. The stalls, paddocks, fence posts, and tack must all be cleaned and disinfected.  The horse’s bedding needs to be replaced and the pasture cleaned of any manure. 

If the complete blood count (CBC) determined a bacterial infection, the patient will be prescribed an antibiotic. Antibacterial ointment may be recommended for abrasions or lesions on your horse’s skin.

Recovery of Oxyuris sp in Horses

A follow up visit is usually recommended two weeks after the first dose of the dewormer. The veterinarian will take a second scraping to check for oxyuris sp.  A second dose of the dewormer may be required if the parasites are still present. 

To avoid re-infestation of oxyuris sp, the horse should be dewormed on a regular basis.  The veterinarian can help you determine what dewormer to use and the correct dosage for your horse. Stalls, paddocks, bedding and pastures should be cleaned daily.  It is recommended that feeding trays be used instead of feeding the horse on the ground.  New incoming horses should be tested for parasites before being allowed into the stalls and/or pasture.

In some cases of oxyuris sp infestation, it may take months to fully eliminate the parasites.  It is important to follow the veterinarian’s treatment plan and maintain a clean environment.