Canada’s horse industry has been asked to halt imports of U. S. breeding stock, embryos or semen while inspectors check farms that may have used semen infected with a contagious reproductive disease.
The Canadian Food Inspection Agency (CFIA) on Dec. 24 confirmed that farms in Ontario and Alberta received semen this spring taken from one of three Kentucky stallions that have since tested positive for contagious equine metritis (CEM).
CFIA and provincial animal health officials are now tracing the semen shipments to identify potentially exposed animals.
CFIA said it has quarantined animals on the Canadian farms in question and these quarantines will stay in place until all animals have tested negative for CEM.
CEM affects infected horses’ reproductive tracts and can cause temporary infertility in mares. Infected animals may not show symptoms, though, so CEM can be tough to detect and control.
While CEM is usually treatable with antibiotics and disinfectants, it remains a reportable disease in Canada.
CEM spreads directly during natural breeding, but can also be transmitted during artificial insemination and through contaminated instruments and equipment, such as tail bandages, buckets, sponges and gloves. Horse owners and veterinarians should thus maintain strict hygiene when handling breeding mares and stallions to prevent infection.
Infected stallions tend to be the major source of infection, as they show no clinical signs but can carry CEM bacteria on their external genitals for years.
The primary symptoms of infection in mares are short-term infertility and vaginal discharge, but some mares can also carry the disease without clinical signs.
According to a 2005 fact sheet from the U. S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS), the first cases of CEM to reach the U. S. were in Kentucky in 1978 and Missouri in 1979, but the disease was “eradicated” from both states and hadn’t since been found in the horse population.
In mares, acute infections show up as an “obvious, thick, milky, mucoid vulvar discharge” 10 to 14 days after breeding. Chronic infections, however, show less-obvious discharge and may be tougher to stamp out of a herd.
Other mares may carry the bacteria for months and infect other animals while not showing any symptoms. Mares can’t be treated until CEM bacteria clears out of its uterus, and that process may take months.