Listen: Equine Reproduction Expert Tells You What You Need To Know About Equine Herpesvirus
As foaling season approaches, the Ontario Animal Health Network has released a podcast for horse owners about the dangers of Equine Herpesvirus for broodmares. Dr. Tracey Chenier is an associate professor of theriogenology at the Ontario Veterinary College and provided listeners with perspective on how prevalent the virus is and what breeders can do to combat it.
Chenier says research shows 50 to over 80 percent of horses have antibodies to EHV, meaning they've been exposed to it at some point in their lives, even if they didn't show symptoms. Most people think about EHV as causing respiratory illness which can travel through show grounds or racing barns, but it can also cause abortions for pregnant mares. The virus starts in the respiratory system and can settle in the lymphatic system, then travel to other parts of the body, threatening a pregnancy.
The spread of equine herpesvirus is often discussed in the context of the respiratory version of the illness, in which it can be spread through nasal secretions, but Chenier reminds the audience that if EHV causes an abortion, the resulting tissues and fluid from the mare and the aborted fetus are also "absolutely full of virus." These should be treated as potential biohazards if there are other pregnant mares on the farm.
Chenier says it's not possible to know whether a mare on the farm is shedding the virus and posing a threat to others, because many don't show symptoms while shedding the virus, and silent carriers of the virus are known to start and stop shedding at different times during the year. Virus shedding is often prompted by physical, environmental, mental, or social stressors.
"You have to remember that in the case of herpesvirus, the infection's taking lace weeks and even months before the abortion," she said. "That happened long ago and the abortion's just the later result of that infection. Other than good biosecurity following abortion to reduce the risk for other mares on the farm, there's not really a treatment, per se."
Vaccinating for EHV during an outbreak is controversial, Chenier said, but there are certain situations where it may make sense based on a mare's most recent booster date.
Listen to the full podcast here.
