The Department of the Environment, Food and Rural Affairs (DEFRA) has confirmed the isolation of Taylorella equigenitalis (the Contagious Equine Metritis organism) from an asymptomatic 16-year-old thoroughbred mare in Gloucestershire. According to the owner, this retired National Hunt race mare has never been covered by a thoroughbred stallion and has never been pregnant, but was unsuccessfully inseminated with semen from a non-Thoroughbred stallion last season, that has now also been tested positive for T. equigenitalis.

The only other mare on the owner’s premises is a nine-year-old non-thoroughbred mare that is reported to have been previously neither covered, nor inseminated. Clitoral swab samples taken from this mare suggest that she is positive also and therefore may have been laterally contaminated.

All positive horses are under official breeding restrictions, and must be treated and tested according to the Horserace Betting Levy Board’s Codes of Practice before these restrictions will be lifted.

The Thoroughbred Breeders’ Association recommend that veterinary surgeons attending thoroughbreds and horses of other breeds should continue to recommend that their clients follow the HBLB’s Codes of Practice (, making sure that all stallions, teasers and mares are specifically tested and cleared negative for CEM before they are used for any breeding purposes.

These Codes of Practice are designed to help maintain freedom from CEM and other important equine infectious diseases and after over 30 years of consistent use in UK have proved highly successful.

Also, and particularly following this news, veterinary surgeons should help make sure that their clients clearly understand and apply these well established principles of biosecurity, and more specifically to consider and take steps to minimise the risks of transmission from any sectors of the horse breeding industry that may not fully apply the Codes of Practice.

In view of this recent report, all breeders must remain even more vigilant.

There is no evidence to suggest that this outbreak involves the UK’s Thoroughbred breeding industry, where the application of the Codes is standard practice.

A formal letter notifying the veterinary profession and recommending vigilance, signed by the TBA’s Veterinary Advisors, Professor Sidney Ricketts and James Crowhurst, Dr. Richard Newton, Head of Epidemiology and Surveillance at the Animal Health Trust and by Professor Nigel Gibbens, DEFRA’s Chief Veterinary Officer, has been submitted for publication to the Veterinary Record, the British Veterinary Association’s weekly professional journal.

For more information contact the TBA on 01638 661321, or your veterinary advisor.