What is Contagious Equine Metritis (CEM)? Contagious Equine Metritis (CEM) is a sexually transmitted disease among horses caused by a bacteria Taylorella equigenitalis. Clinical signs may include a mucopurulent vaginal discharge in up to 40% of affected mares, abortion and infertility. Stallions typically show no clinical signs. Stallions and mares can become chronic carriers of CEM and be sources of infection for future outbreaks. The transmission rate is high and naturally occurs by mating, but contaminated instruments and equipment may be an indirect source of infecting mares and stallions. The bacteria can also be spread via semen collected for artificial insemination. How is CEM Transmitted: CEM is commonly transmitted directly during sexual intercourse between undetected CEM – positive breeding mares and stallions. Transmission may also occur indirectly by artificial insemination or contact with fomites, such as contaminated hands or instruments. Outbreaks usually occur at breeding facilities following international horse shipments.Undetected carrier mares and stallions are the source of infection for acute outbreaks of the disease. During the breeding season, a carrier stallion may infect several mares before the disease is suspected or diagnosed. What happens to CEM positive horses? CEM can be treated with disinfectants and antibiotics. CEM-positive mares, and mares from CEM-positive countries, are required to go through a treatment protocol and remain in quarantine for no less than 21 days. Stallions that have CEM or come from a CEM-positive country are required to remain quarantined until a treatment protocol is completed and they test negative for the disease. How do you treat CEM? The mare cannot be successfully treated until the CEM bacteria clear from the uterus, a process that may take several months. The external genitalia of the mare and stallion can be treated with disinfectants and antibiotics. Once daily for 5 consecutive days, the external genitalia should be gently scrubbed with 2% chlorhexidine in a mild detergent solution and rinsed with a warm saline solution. The external genitalia should then be coated with an antibiotic ointment, such as nitrofurazone. Due to the effectiveness of this treatment, surgical removal of the clitoral sinuses is rarely required. How do you prevent and control CEM? Quarantine and test all imported fillies, mares, and stallions of foreign origin, and mares and stallions not previously bred in the United States that are older than 731 days (2year). Quarantine and test the first three mares bred to a stallion of foreign origin. Quarantine all suspects until all test results are negative. Avoid breeding any CEM-positive horses until they have been successfully treated and certified CEM negative. Maintain strict hygiene when handling mares and stallions e.g., use disposable gloves, change gloves between horses, and thoroughly clean and disenfect instruments. This information has been provided by the United States Department of Agriculture
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