C   back to resource centre home   Contagious Equine Metritis By Horse SA www.horsesa.asn.au Contagious Equine Metritis (CEM) is a horse STD (sexually transmitted disease) causing vaginitis and endometritis which results in infertility and occasional abortion in mares. Infection is transferred between horses during service but stallions show no signs. Chronically infected mares are the main reservoir of infection, but congenitally infected foals can also become long term carriers. CEM is an exotic disease to Australia. There have been no clinical cases of CEM in Australia since 1978. CEM usually causes an odourless discoloured discharge (mucous and pus) from the vulva. The discharge normally appears 1-6 days after infection (during service) but can be delayed up to 80 days. Mares may return to heat a few days after infection. Detecting infection can be difficult because the discharge usually disappears after 1-4 weeks so it can be easily missed in paddock situations. Sometimes there is no discharge at all. Reproductive tract swabbing of suspicious mares by a veterinarian and laboratory testing is required to diagnose the condition, and it can be treated with antibiotics. Endometritis in Australian mares is usually caused by infection with other bacteria (most often Streptococcus, E coli, Pseudomonas, Klebsiella or Staphylococcus) or yeasts. This is usually related to confirmation defects of the mare's vulva or local problems within the reproductive tract, but may also involve poor stud hygiene . There may or may not be vulval discharge, so reproductive loss (failure to conceive or maintain pregnancy) in mares may be the only detectable sign. There is also a risk of endometritis at foaling (usually from retained membranes of trauma to the mare during foaling). Endometritis may lead to permanent infertility and can be complicated by septicaemia and laminitis. CEM still exist in other countries and endometritis or vaginitis from infections common in Australian mares cannot be distinguished from this exotic disease without lab testing. Although Australia has requirements for imported live horses and biological material like semen to prevent the entry of exotic diseases like CEM, owners or managers observing vulval discharge, infertility or reproductive loss in mares should contact their private veterinary practitioner promptly for advice.