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Also Known As

Testicle infection or inflammation


Orchitis is an infection or inflammation in a male horse's testes. Orchitis can be bacterial, viral, parasitic, or auto-immune in origin and can develop either one of both testes.

Upon examination, the horse's semen, if it can be obtained, usually shows that spermatozoal motility or ability to move is decreased and abnormalities in the sperm are present. If not treated properly, a testicular abscess may develop.

Epididymitis, the inflammation of the coiled tubles on top of the testicle, may be present. The infection starts in the urethra and works its way to the testicle.


  • Hard, swollen mass in the scrotum
  • Pain
  • Elevated testicular temperature
  • Decrease in semen quality, motility, and increase in abnormal forms
  • A hopping gait because of discomfort


A number of diseases and conditions can lead to orchitis with the most common cause being sexually-transmitted bacterial infections, including Streptococcus zooepidemicus, an infection that starts in the urethra and works its way to the testicle.

In addition to Strep zooepidemicus, Klebsiella, Salmonella, Influenza virus, viral arteritis, and equine infectious anemia can also lead to orchitis which may result from an ascending infection from the outside of the horse's body or a spread of a systemic internal infection.

Orchitis may also be caused by testicular cord torsion resulting in interference with circulation and infarction of the testes.

In addition, trauma to the testes and inflammation of the testicular artery due to migrating strongyle larvae may result in orchitis.

Although not frequent, viral orchitis may be the cause of testicular degeneration as a result of equine influenza, viral arteritis, and equine infectious anemia.

Parasitic orchitis is associated with the migration of Strongylus edentatus causing testicular irritation and adhesions.

Auto-immune orchitis may result from testicular trauma and damage to the blood-testis barrier.


Good horse management to prevent infection or injury to the horse's testicles is important. Also, keeping horses healthy with an appropriate diet, plenty of exercise, and prompt attention to the earliest signs of disease will be helpful in preventing diseases that affect the testicles.

Keeping stallions from associating or interacting with other horses that have sexually-transmitted bacterial infections will help reduce the number of occurrences. Careful screening is necessary.

Proper sanitation practices and disinfecting of premises on a regular basis helps in many cases.


Ice packs and cold water hydrotherapy should be applied to the scrotum to reduce pain and swelling. An external support to elevate the testicles will relieve pressure.

High levels of systemic antibiotics for several days may be recommended by a veterinarian. Ultrasound of the testicle can be used to distinguish between infection and trauma and to determine if the epididymitis is involved.

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EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.