CEM stands for contagious equine metritis, which is essentially inflammation of the uterus of a mare, which in this case is caused by a sexually transmitted infection. CEM, despite the name, does also occur in geldings and stallions, but it is the mare who suffers the negative impact of the disease.
What is CEM?
The bacteria responsible for CEM is called Taylorella equigenitalis. CEM can be passed from horse to horse during mating or by infected instruments used by vets. Even a teaser stallion, sniffing at the genitals of an affected mare, can carry the disease to the next mare he teases. The dark, greasy substance within the sheath of stallions can be a haven for bacteria, and if a ‘phantom’ is used for collecting semen, these bacteria, including Taylorella equigenitalis, can be directly passed on to the next stallion. Even infected geldings can transmit the disease if they attempt to cover mares.
CEM has serious effects. In South Africa, no stallion may be used for breeding (naturally or using artificial insemination) without an official CEM clearance certificate. The condition itself is relatively easily treatable, although treatment is expensive, but the loss of foals in early pregnancy and the costs associated with this can be devastating for breeders.
Symptoms
Stallions with CEM and many mares, especially those who are chronically infected, may show no signs of the disease, but are still able to transmit it to other horses. Around 40% of the mares who have acutely contracted the disease display a grey to creamy vaginal discharge approximately 10 to 14 days after mating with the infected stallion or being inseminated with infected semen. The acute CEM infection makes most mares infertile, and some mares may lose their foals, but the infertility tends to only be problematic for a few weeks, after which pregnancy becomes possible again.
Most mares will recover from CEM with no intervention, but many of them become carriers of the infection, so they can pass it on to stallions they breed with in the future. Stallions, on the other hand, all become carriers and continue to transmit the disease until it is detected and treated.
Diagnosis
Diagnosis is made by taking samples from all accessible sites and then looking for the responsible bacteria. In stallions, samples are taken from the sheath and urethra, and the procedure is then repeated again seven days later. In the mare, a bacterial culture is taken from the endometrium (the lining of the uterus), the cervix and the external genitalia. Samples must be immediately refrigerated and taken to a lab which offers testing, so that they can be tested within 48 hours of collection.
Blood tests are available for mares to look for antibodies to the bacteria, but these same tests cannot be used in stallions. These blood tests only become positive in a mare after about 10 days post infection. If the mare is positive, the blood tests tells you only that the mare has had the disease at some stage, not that she is necessarily an active carrier of the disease now.
Stallions in South Africa are not permitted to breed without an official CEM clearance certificate for the current breeding season. To be issued with the certificate, both CEM tests (seven days apart) must be negative. Mares do not require testing.
Treatment
The bacteria responsible for CEM is responsive to most antibiotics, although the carrier state in mares can be trickier to treat. Recommended therapy is to infuse the uterus with an antibiotic, and cleanse the clitoral area and sinuses with disinfectant, and then apply antibiotic cream. This treatment is repeated daily for about five days.
It is simpler to eradicate the carrier state in stallions, using local disinfectant. With the stallion’s penis dropped, the shaft of the penis, including the urethral fossa, should be cleansed daily for approximately five days with disinfectant solution. After drying, antibiotic cream can be applied to the area.
Prevention
As CEM is readily identifiable using diagnostic tests, all breeders need to ensure that their stallions are tested, and that instances of the disease are given prompt and thorough treatment. Breeders must also ensure that any imported semen or horses brought in to their yard for breeding, have the appropriate CEM clearance. As the disease is so readily detectable diagnosis can be prompt, so that treatment can be instigated before the infection can be transmitted. This will prevent any large-scale outbreaks of CEM in South Africa.