Contagious Equine Metritis - Stallion

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Also Known As

Venereal disease in stallion


Contagious equine metritis in stallions is reported to be the most contagious bacterial venereal infection of horses and should be suspected any time several mares develop the clinical signs after having been bred to the same stallion.

In stallions, the contagious equine metritis organism is carried on the external genitalia and may exist in place for years. Isolation of Taylorella equingenitalis is sometimes difficult. In stallions, when the organism is suspected, cultures can be taken from the urethra, urethral fossa and diverticulum, and the sheath for testing to determine the presence of the disease-causing organism.


  • Stallions are asymptomatic and the disease is usually identified only after several mares become infected after being bred to the same stallion.


The disease is caused by two strains of Taylorella equingenitalis, one sensitive and the other resistant to streptomycin. Infected animals are identified by culturing, and successive negative tests are required after treatment to ensure the animal is negative before breeding.


Since the disease is usually transmitted during the mating process, a careful program of disease prevention should be in place. Special care should be taken to prevent potentially infectious mares or stallions from becoming part of the breeding program.

If a stallion becomes infected, careful attention should be paid to the mares that have been bred recently to determine the carriers of the organism. Strict import regulations have helped eradicate the disease in the United States.

In addition to careful selection of breeding animals, special care should be taken with all equipment that stallions are exposed to in the breeding or daily living process. Control of CEM depends on identification of infected carrier animals and on their treatment or elimination from the breeding program.


When a stallion is diagnosed with contagious equine metritis, the external genitalia (extended penis, sheath, and prepuce) should be thoroughly cleaned with chlorhexidine surgical scrub and then treated by applying nitrofurazone ointment.

Care should be taken to make sure all smegma is removed from the urethral fossa to ensure best results from the treatment with the ointment. This should be done daily for five days and the stallion should be retested ten days after the treatment.

Outbreaks of this disease are sporadic and no fatal infections have been reported.

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