Last Updated on February 21, 2022 by Allison Price
Contagious Equine Metritis and Equine Viral Arteritis (STDs) are sexually transmitted diseases that affect horses. They can cause problems like low conception rates, abortions, sick or weak foals, as well as other issues such as low fertility rates and poor health. These diseases can have a negative economic impact on breeding because they can disrupt breeding plans, are expensive to treat and sometimes, are difficult to eradicate completely from infected animals.
CEM (contagious equine metris) was first described in England in 1977. It was then reported in the United States within a few years. This bacterial infection was found in many countries, including Japan, France, Germany and France.
Stallions do not show signs of infection but can transmit the disease to mares through breeding. Although infected mares might not show any symptoms, they can develop a creamy vaginal discharge two weeks after being bred with an infected horse. The majority of mares are not very sick and can recover without antibiotics. However, they won’t have been able to conceive from the breeding. After the acute infection has subsided, fertility returns. However, these mares may have lost up to a month of their breeding season so they might not be able to produce foals for the year. Asymptomatic carriers may be able to transmit the disease to the next breeding to another mare if they are not treated.
CEM can be caused by artificially inseminating mares with the semen of infected stallion if they are not treated with antibiotics. This scenario could lead to many horses being infected. To ensure that breeding stallions are healthy before the season starts, it is possible to test them.
Equine viral arthritis, also known as EVA, is another problem that horse breeders face. Although this is an STD, it can be spread from horse to mare by nasal secretions. Even if the horses are not showing any signs of disease, semen can be found from infected stallions. These stallions can cause mild upper respiratory diseases in mares that are bred with their semen. However, these symptoms may not be obvious and may go unnoticed. Although the mare is now a carrier of EVA, she usually gives birth to a healthy foal. However, if she is turned out alongside other late-pregnant mares the mare may contract the virus from their nasal secretions and/or coughing. Even if the mares are healthy, some of these mares may experience late-term abortions . EVA can be prevented by vaccinating mares before they are bred.
It is interesting to note that Standardbreds as well as Warmblood horses are more sensitive to EVA infection than other breeds. There have been few late-term abortions even among infected mares. Quarter Horses and Thoroughbreds, on the other hand have far fewer carriers but are more likely to lose their pregnancies due to the virus.