Contagious Equine Metritis

Also see: https://codes.hblb.org.uk/downloads/2026/CEM.pdf

• Clitoral swabs must be mini-tipped (as impossible to swab clitoral sinuses with standard size)
• Swabs for culture must be in Amies Charcoal Medium
• Expiry date of swab must be visible and not expired
• Swabs for culture must be in the laboratory within 48 hours of collection (no time constraints for qPCR)

Contagious Equine Metritis may be caused by 3 bacteria:

• Taylorella equigenitalis (contagious equine metritis organism (CEMO))
• Klebsiella pneumoniae (capsule types 1, 2 and 5 only)
• Pseudomonas aeruginosa -although not all P. aeruginosa strains are venereal pathogens, it must be assumed that they are in the absence of any current laboratory methods to differentiate them.

Isolation of T. equigenitalis is notifiable. K. pneumoniae and P. aeruginosa are not notifiable although it is advised that infection in stallions is reported to the national breeders’ association.

Although infection in mares may cause a vulval discharge and early return to oestrus post-breeding, mares can also carry the infection (primarily clitoris, clitoral fossa and sinuses and sometimes urethra/bladder) without detectable clinical signs. Stallions generally carry infection silently on their penis, sheath and sometimes in the urethra and bladder although may rarely show clinical signs of purulent semen.

Low risk mares and stallions are any not defined as high risk as below:
High risk mares:

• T.equigenitalis, K. pneumoniae capsule types 1, 2 or 5 or P. aeruginosa has been isolated in the past.
• visited any premises on which T.equigenitalis has been isolated within the previous year;
• mated during the last breeding season with stallions resident outside France, Germany, Ireland, Italy and the UK
• been in countries other than France, Germany, Ireland, Italy and the UK within the last 12 months

High risk stallions:

• Stallions which have not previously been used for breeding
• T.equigenitalis, K. pneumoniae capsule types 1, 2 or 5 or P. aeruginosa has been isolated
• been at any premises on which T.equigenitalis, K. pneumoniae capsule types 1, 2 or 5 or P. aeruginosa has been isolated in the last year
• mated a mare which has not been swabbed negative in accordance with the Code of Practice.

After 1st January, and before a mare is mated/teased/inseminated, negative swabs (using mini-tipped swabs) must be obtained as follows:

If any mare returns to oestrus at an unusual (especially shorter than normal) time, repeat clitoral and endometrial swabs should be taken (aerobic and microaerophilic or PCR).
If any mare changes premises, or stallions, repeat clitoral and endometrial swabs should be taken at least seven days after mating by the original stallion.

After 1st January and before a stallion is used for mating/teasing/semen collection, 2 sets of negative swabs taken ≥7 days apart must be obtained from the urethra, urethral fossa and penile sheath, plus pre-ejaculatory fluid when possible (cultured aerobically and microaerophilically or PCR).
‘High risk’ stallions and stallions standing on a stud also require the first four mares mated with them to be screened for T.equigenitalis, K. pneumoniae capsule types 1, 2 and 5 and P. aeruginosa by taking a clitoral swab two days after mating. If the mare subsequently returns to oestrus, an endometrial swab should be taken at that time. These swabs should always be tested aerobically and microaerophilically or PCR. In addition, mid-season swabbing should be considered for all stallions and teasers.

• All swabs should be taken by a veterinary surgeon.
• Clitoral swabs must be on mini-tipped swabs (as it is impossible to enter the clitoral sinuses with a standard swab).
• place swabs in Amies Charcoal Transport Medium (must be within the expiry date)
• label with
  o date and time collected
  o horse’s name
  o site of swabbing;
• submit them to a HBLB Registered Laboratory for testing
• swabs for microaerophilic culture for T.equigenitalis must arrive in the laborator

Liphook Equine Hospital is a BEVA registered laboratory for both CEM culture and PCR. Microaerophilic culture results (T.equigenitalis) will not be available for 7 days and aerobic culture results (K.pneumoniae, P.aeruginosa) will not be available for 48 hours. PCR test results should be available on the day of arrival at the laboratory.

Swabs taken for export must be sent to the APHA laboratory, Penrith.