Equine coital exanthema is believed to only be transmitted during the acute phase of the disease through serous fluid from the blisters during sexual intercourse, and via breeding tools, handlers, etc.
Clinical signs include cute small lesions, no bigger than 2 mm in diameter around the vulva in mares, and on the sheath in stallions.
[1] While the majority of the symptoms are external, the presence of the virus can cause small and large plaque variants in tissues.
[2] The acute symptoms of contagious equine metritis include acyine inflammation of the uterus, an obvious thick, milky, mucous vulvar discharge 10 to 14 days after a live covering by a stallion.
Chronic symptoms include milder uterine inflammation that will cause less obvious vulvar discharge, and then the infection may be more difficult to eliminate.