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 Wednesday 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 U.S. semen shipments to identify potentially exposed animals, the agency said.
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. “As investigations in Canada and the U.S. continue, animals on additional farms may be quarantined,” CFIA wrote.
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.
“This means that all suspected cases must be reported to the CFIA for immediate investigation by inspectors,” the agency said Wednesday. “There are international trade implications if a country loses its CEM-free status.”
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.
The disease was first seen in the U.K. in 1977 and because of its “insidious nature,” it’s hard to say where it first came from or how far it’s been distributed worldwide, APHIS said.
“When coupled with the fact that mares can be bred only during certain seasons, CEM can have a devastating effect on equine reproductive
efficiency,” APHIS wrote in 2005. “Should CEM become established in the
United States, the horse industry would suffer great economic losses.”
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 vulvar discharge and may be tougher to stamp out of a herd.
Other mares may carry the bacteria for months in their reproductive tracts and infect other animals while not showing any symptoms. In any case, a mare can’t be treated until CEM bacteria clear out of its uterus, and that process may take months.
CFIA asked Wednesday that any Canadian horse owner or veterinarian who suspects a horse in his or her care is infected with CEM should “immediately” contact a CFIA district office.
CFIA and APHIS both say there’s no evidence that CEM has any human health implications.