As of Feb. 18, three more horses had tested positive for a “CEM-like” organism in Kentucky. A Paint stallion and two pregnant mares were cultured positive for the organism on the original nurse mare farm in Kentucky where the organism that causes contagious equine metritis (CEM) was found in late January. Rusty Ford, Equine Programs Manager with the Kentucky State Veterinarian’s Office, said all testing of equids on the 12 premises used by the nurse mare operation has been completed. Now the personnel will focus on trying to complete their epidemiologic study to determine if the current stallion and mares were somehow connected to the original donkey jack and two mares earlier diagnosed as having the organism.

The organism found in the Kentucky donkey jack is “99.9% similar to organism” found in a donkey jack in California. However, that organism is not exactly the same as the one that is scientifically classified as causing CEM.

Questions still need to be answered about whether this “CEM-like” organism is a CEM subset organism, whether it can be transmitted through breeding, and whether it can cause disease (in donkeys or horses). It also raises the question of whether there is an non-horse source (i.e., donkeys or mules) of the CEM organism, or a closely related organism, in this country