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 serious disease because it is highly contagious. When coupled with the fact that mares can be bred at only certain seasons, CEM can have a devastating effect on equine reproductive efficiency. Should CEM become established in the United States, the horse industry would suffer great economic losses.