Taylorella equigenitalis (Contagious Equine Metritis Organism)

Taylorella equigenitalis is the bacterium responsible for Contagious Equine Metritis (CEM), a uterine infection of mares which results in temporary infertility. CEM can cause widespread reduced fertility and serious disruption to breeding operations particularly amongst the Thoroughbred population in which the permitted covering season is short.

Infection spreads mainly through direct transmission of the bacteria from stallion to mare or mare to stallion, at mating. It may also be spread by artifical insemination (AI) if the semen used is from an infected stallion.

Infected stallions do not show signs of disease. Mares may develop varying degrees of vaginal discharge within 2 - 10 days of mating, or may also appear unaffected. Although recovery is usually uneventful, a large proportion of mares will remain carriers of the infection.


Bacterial culture is essential for diagnosis, as similar signs may be caused by other bacteria such as Klebsiella and Pseudomonas species and Streptococcus zooepidemicus.

Swabs should be taken from the clitoral sinuses and fossa of the mare and from the urethra, urethral fossa, penile sheath and pre-ejaculatory fluid (where possible) of stallions. All swabs should be submerged in Amies Charcoal Transport Medium and sent immediately to an approved laboratory.


Mares and stallions require 5-7 days of careful washing with 2% chlorhexidine, combined with local and systemic antibiotics. Mares with signs of uterine infection require daily intrauterine antibiotic irrigations. Follow-up swabs are taken to assess the success of treatment. Occasionally treatment needs to be repeated. In some mares with intractable clitoral infections, surgery to remove the affected tissue is indicated.


The principal means of control is by the identification of infected animals before breeding commences. These animals should not be used for breeding until the infection has been successfully treated. All stallions and mares should be thoroughly screened for T. equigenitalis (and Equine Viral Arteritis) at the beginning of each breeding season.

In the UK, isolation of Taylorella equigenitalia is notifiable by law to the Ministry of Agriculture, Fisheries and Food (MAFF).

The Horserace Betting Levy Board produces Codes of Practice for the prevention and control of CEM, Klebsiella and Pseudomonas, along with other important equine infectious diseases.

These codes outline the minimum measures which should be implemented by horse owners, in conjunction with their veterinary surgeons, as a means of limiting and resolving disease outbreaks. Copies of the Codes of Practice are available from:

Horserace Betting Levy Board
52 Grosvenor Gardens

Tel: 020 7333 0043
Fax: 020 7333 0041
Email: hblb@hblb.org.uk

Strict adherence to the Codes of Practice along with good stud management and hygiene should prevent introduction and spread of disease onto and within farms.

To find out more about the AHT why not visit their website www.aht.org.uk


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