Contagious Equine Metritis

What is contagious equine metritis?

Contagious equine metritis (CEM) is a transmissible venereal disease in horses, caused by a bacterium called Taylorella equigenitalis. CEM is highly contagious and can have a devastating effect on equine reproductive activity. This disease occurs naturally only in horses, and all breeds are susceptible.

Where is CEM found?

This disease was first described in Newmarket, United Kingdom, in 1977. Today, it exists primarily in non-thoroughbred populations throughout the world. Cases are occasionally detected in mares and stallions imported from other countries into Canada.

How is CEM transmitted and spread?

The disease is primarily spread during natural breeding. Infected stallions tend to be the major source of infection, as they can harbour the disease for years without showing any clinical signs.

CEM can be transmitted indirectly to mares and stallions via contaminated instruments and equipment such as tail bandages, buckets, sponges and gloves. The bacteria can also be transmitted via artificial insemination. It is advisable to maintain strict hygiene when handling breeding mares and stallions to prevent disease transmission.

Is CEM a risk to human health?

There is no human health risk associated with CEM.

What are the clinical signs of CEM?

Stallions do not usually show any clinical signs of infection. However, the infected stallion remains capable of transmitting disease.

In mares, initial exposure to the disease usually results in a large amount of vaginal discharge 12 to 14 days following natural breeding with an infected stallion. The disease can cause infertility and, on the rare occasion, abortion. The severity of disease in mares varies. There are two states of infection:

• Active state: The main outward sign is a vaginal discharge which may range from very mild to extremely prolific.
• Carrier state: There are no outward signs of infection; however, the mare remains capable of transmitting infection.

How is CEM diagnosed?

CEM is suspected when multiple mares that are bred by the same stallion experience short-term infertility and have vaginal discharge. Diagnosis depends on isolating and identifying the bacteria in a laboratory.

How is CEM treated?

In most cases, CEM can be successfully treated with disinfectants and antibiotics. While one course of treatment may be sufficient in a stallion, it may take several months before the CEM organism can be successfully treated in a mare. Once the organism has been eliminated, the horse may be used for breeding again.

What roles and responsibilities exist to prevent CEM?

CEM is a "reportable disease" under the Health of Animals Act. This means that all suspected cases must be reported to the Canadian Food Inspection Agency (CFIA) for immediate investigation by inspectors.

All horses of breeding age that are imported into Canada from countries where CEM is known to occur must be tested for CEM before entering Canada. After entry into Canada, both stallions and mares are quarantined, where they undergo further extensive testing. Foals less than two years old and geldings are not required to be tested for the disease.

If CEM is found in Canada, the policy is to eradicate the disease. Eradication involves implementing disease control measures such as quarantines, movement restrictions, testing of exposed horses, and treatment of infected horses.

The CFIA imposes strict regulations on the import of animals and animal products from countries where CEM is known to occur. These regulations are enforced through port-of-entry inspections done either by the Canada Border Services Agency or the CFIA.

Canada is currently assessing the situation in the United States with Government regulatory officials, with a view to adopting additional requirements for imports into Canada, in response to the change in the status of the disease in the United States.

For more information

Contact your CFIA Area office:

Atlantic Area: 506-851-7651

Quebec Area: 514-283-8888

Ontario Area: 519-837-9400

Western Area: 403-292-4301

You can find your local CFIA District office on the CFIA Web site or by consulting the blue pages of your local phone directory.