Contagious equine metritis (CEM) is a trans-missible, exotic, venereal disease of horses caused by the bacterium Taylorella equigenitalis. Thoroughbred horses appear to be more severely affected by the disease than other breeds. Because animals may be asymptomatic, the disease is difficult to detect and control. There is no evidence that CEM affects people.

CEM is a venereally transmitted bacterial disease of horses. CEM was first reported in the UK in 1977 but this country is now free of this disease. CEM still occurs in a number of other EU countries, including the Scandinavia countries, as well as in Morocco and Japan.