Fact Sheet - Contagious Equine Metritis

What is contagious equine metritis?

Contagious equine metritis (CEM) is a transmissible venereal disease in horses, caused by the bacterium Taylorella equigenitalis . CEM is highly contagious and can have a devastating effect on equine reproduction. This disease only affects horses, however all breeds are susceptible.

Is CEM a risk to human health?

No. 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 rare occasions, 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.

Where is CEM found?

CEM has never been detected in Canada but does exist primarily in non-thoroughbred populations throughout the world.

How is CEM transmitted and spread?

The disease is primarily spread directly 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 disease can also be transmitted via artificial insemination. It is advisable to maintain strict hygiene when handling and breeding mares and stallions to prevent disease transmission.

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. Laboratory testing is needed to confirm the diagnosis.

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 is being done to protect Canadian horses from CEM?

All horses of breeding age that are imported into Canada, from countries where CEM is endemic, must be tested for the disease before entering Canada. After entry into Canada, both stallions and mares are quarantined, where they undergo further extensive testing.

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.

How would the CFIA respond to an outbreak of CEM in Canada?

Canada's emergency response strategy to an outbreak of CEM would be to:

  • eradicate the disease; and
  • re-establish Canada's disease-free status as quickly as possible.

In an effort to eradicate CEM, the CFIA may employ some or all of the following disease control methods:

  • the treatment of infected horses;
  • surveillance and tracing of potentially infected or exposed animals;
  • strict quarantine and animal movement controls to prevent spread;
  • strict decontamination of infected premises; and
  • zoning to define infected and disease-free areas.

Additional information

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