Contagious Equine Metritis
Contagious equine metritis (CEM) is a highly contagious venereal disease of horses that causes an acute purulent metritis 10 to 14 days post breeding to an infected stallion. Mares may become chronically infected and remain carriers of the causal organism for several months or longer. Stallions carry the contagious equine metritis organism (CEMO) on their external genitalia and the primary site of localization is the urethral fossa. The stallions may carry the CEMO on their external genitalia for years. Newborn foals may become infected at birth and remain infected until they are mature.
The CEMO is a microaerophilic gram-negative coccobacillus. There are two important strains of the CEMO, one being streptomycin sensitive and the other streptomycin resistant. A suggested name, Taylorella equigenitalis, has recently been accepted by the International Committee on Systemic Bacteriology.
The disease is naturally transmitted by coitus. Undetected carrier mares and stallions are the source of infection for acute outbreaks of the disease. Also, the CEMO may be transmitted through the use of artificial insemination.
In both the acute and chronic stages of the disease, isolation of the bacterium is necessary for a diagnosis of CEM. Culture sites in the mare are the uterus, clitoral fossa and clitoral sinus (or endometrium). In the stallion, the culture sites are the urethra, urethral fossa and diverticulum and the sheath. Culture swabs should be placed immediately in Amies transport media and maintained at 4° C or lower to prevent the organism from dying and to prevent overgrowth by contaminating bacteria. If the culture swabs are not cultured within a few hours, the specimens in the transport media should be frozen. The organism appears to remain viable when frozen, for it has remained viable in Amies transport media for 18 Years at -20° C.
There is no evidence that man is affected by the CEMO.