Equis ISSN 2398-2977

Uterus: contagious equine metritis

Synonym(s): Taylorella equigenitalis, CEM

Contributor(s): Terry Blanchard, Graham Munroe, Prof Peter Timoney, Vetstream Ltd, Elaine Watson, Madeleine L H Campbell


  • Cause: Taylorella equigenital is, a gram negative, coccobacillus.
  • Signs: vulval discharge, lowered conception rates, infections, endometritis, vaginitis, cervicitis, abortion (rare).
  • Diagnosis: microbiology, seriology, PCR.
  • Treatment: intrauterine infusion of crystalline penicillin solution; chlorhexidine to clean out clitoral sinuses; re-establish normal clitoral flora; systemic antibiotics for chronic endometritis +/- salpingitis; clitoral sinusectomy.
  • Prognosis: guarded if occurrence of carrier state; good with early intrauterine antimicrobial therapy.
Print off the Owner factsheet on Contagious equine metritis (UK/Europe) or Contagious equine metritis (USA) to give to your clients.



  • Taylorella equigenitalis Taylorella equigenitalis, a gram negative, coccobacillus that does not grow serologically on conventional media.
  • Pin-point colorless colonies after 3-7 days microaerophilic culture on enriched 'chocolate' agar Taylorella equigenitalis: culture - chocolate agar.
  • Two strains exist, streptomycin resistant and sensitive.


  • Contact with a carrier stallion, mare, or fomite spread by handlers and vets.
  • Natural breeding or artificial insemination.


  • Spread from an acutely infected or carrier mare.
  • Spread from a carrier stallion.
  • Infection can be spread venereally at breeding, or indirectly by personnel and contaminated fomites.
  • Bacterial invasion of the uterus → acute inflammatory response with an influx of neutrophils to the endometrium Endometrium: endometritis acute - histology  Endometrium: endometritis chronic - histology usually about 2 days post-mating.
  • Smears of discharge may show the organism within the neutrophils.
  • Acute self-limiting infection which may → carrier state.
  • Potentially, foals born to mares which harbor CEM in the uterus during pregnancy may be born infected.


  • Incubation: 2-7 days post-breeding or exposure.
  • Duration of the disease tends to be short.
  • The carrier state can persist indefinitely.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Breuil M F et al (2015) Contagious equine metritis cases reported in France since 2006. Vet Rec 177 (13), 340 PubMed.
  • Schulman M L et al (2013) Contagious equine metritis: artificial reproduction changes the epidemiologic paradigm. Vet Microbiol 167 (1-2), 2-8 PubMed.
  • Timoney P J (2011) Horse species symposium. Contagious equine metritis: an insidious threat to the horse breeding industry in the United States. J Anim Sci 89 (5), 1552-1560 PubMed.
  • Ousey J C et al (2009) An investigation into the suitability of a commercial real-time PCR assay to screen for Taylorella equigenitalis in routine prebreeding equine genital swabs. Equine Vet J 41 (9), 878-882 PubMed.
  • Watson E (1997) Swabbing protocols in screening for contagious equine metritis. Vet Rec 140, 268-271 PubMed.
  • Timoney P J et al (1996) Contagious equine metritis. Comp Immunol Microbiol Infect Dis 19 (3), 199-204 PubMed.
  • Timoney P J et al (1985) Contagious equine metritis, experimental infection in the donkey. Vet Microbiol 10 (3), 259-268 PubMed.
  • Dolan M et al (1984) Serologic and bacteriologic survey of three horse studs for contagious equine metritis. Aust Vet J 61 (1), 17-19 PubMed.
  • O'Brien J J et al (1982) CEM (contagious equine metritis) in Northern Ireland. Vet Rec 111 (17), 400 PubMed.
  • Timoney P J et al (1982) Isolation of the the contagious equine metritis organism from colts and fillies in the United kingdom and Ireland. Vet Rec 111 (21), 478-482 PubMed.
  • Timoney P J et al (1982) CEM (contagious equine metritis) in the republic of Ireland. Vet Rec 111 (17), 400-401 PubMed.
  • Rommel F A et al (1981) Contagious equine metritis; antibody response of experimentally infected pony mares. Vet Immunol Immunopathol 2 (3), 201-213 PubMed.
  • Sahu S P et al (1980) CEM bacteria. Vet Rec 107 (18), 432 PubMed.
  • Sahu S P et al (1980) Contagious equine metritis; isolation and characterization of the etiologic agent. Am J Vet Res 41 (9), 1372-1382 PubMed.
  • Sahu S P et al (1980) Contagious equine metritis; effect of intrauterine inoculation of contagious equine metritis agent in pony mares. Am J Vet Res 41 (1), 5-9 PubMed.
  • Chandler N et al (1979) Swabbing mares and stallions for contagious equine metritis. Vet Rec 105 (24), 561 VetMedResource.
  • Falconer-Taylor R A et al (1979) CEM sampling. Vet Rec 104 (25), 585 PubMed.
  • Swerczek T W et al (1979) Contagious equine metritis-outbreak of the disease in Kentucky and laboratory methods for diagnosing the disease. J Reprod Fertil Suppl 27, 361-365 PubMed.
  • Swaney L M et al (1978) CEM; bacteriological methods. Vet Rec 102 (2), 43 PubMed.
  • Timoney P J et al (1978) CEM and the foaling mare. Vet Rec 102 (11), 246 PubMed.

Other sources of information

  • Horserace Betting Levy Board (2017) Codes of Practice. 5th Floor, 21 Bloomsbury Street, London WC1B 3HF, UK. Tel: +44 (0)207 333 0043; Fax: +44 (0)207 333 0041; Email: enquiries@hblb.org.uk; Website: http://codes.hblb.org.uk.
  • Timoney P J (2011) Contagious Equine Metritis. In: Equine Reproduction. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. pp 2399-2409. Wiley-Blackwell, Chichester.
  • Colahan P T et al (1991) Equine Medicine and Surgery. Vol 2. 4th edn. American Veterinary Publications, Inc. ISBN: 0 939674 27 0. pp 1070 (concise summary of main points).



  • Thoroughbred Breeder's Association, Stanstead House, The Avenue, Newmarket, Suffolk, UK. Tel: +44 (0)1638 661321.
  • For non-thoroughbreds; Welfare Department, British Horse Society, Stoneleigh, Kenilworth, Warks, CV8 2LR, UK. Tel: +44 (0)1203 696697.