Department of Livestock

• Mares: will often show copious mucopurulent vaginal discharge, 10 to 14 days postbreeding to an infected stallion. The first indication of infection may be short-cycling followed by a return to estrus. At this time, a mucopurulent vaginal discharge or a dried vaginal discharge can be found on the tail and inside the thighs. Although the discharge subsides after a few days, the mare can remain chronically infected for several months.
  

Most mares will not conceive when infected at the time of breeding. If infected mares do conceive, they may abort the fetus or carry an infected foal to term. The newborn foal may then become a carrier of the causal organism.

There are three general degrees of infection in mares:

• Acute:Active inflammation of the uterus causes an obvious thick, milky, mucoid vulvar discharge 10 to 14 days after breeding. Lesions are not always present with CEM infection. The most severe lesions are present in the uterus and occur at about day 14 postinfection.
• Chronic: Milder uterine inflammation causes less obvious vulvar discharge. Chronic infection may be more difficult to eliminate.
• Carrier: The bacteria are established in the reproductive tract. The mare shows no symptoms, but is still infectious and can remain a carrier for several months or longer.

• Stallions: exhibit no clinical signs but can carry the CEM bacteria on their external genitalia for years.