Protecting Broodmares from EHV-1: What You Need to Know
With foaling season starting this month, now is the perfect time to refresh yourself about diseases that can affect broodmares.
Equine Herpesvirus Type 1 (EHV-1) is a serious threat to broodmares, known for causing late-term abortions, neonatal foal death, and neurological disease. Prevention is a challenge, as the virus is often not cleared from the body at the time a horse is first infected. It may reside in the nervous tissues in a dormant state until reactivated by stress. A study in Australia found that even with a fully vaccinated herd of broodmares, there will be EHV-1 circulating, so preventing and containing EHV-1 abortions is about juggling the many factors that converge to result in abortion. — and that includes minimising mixing, managing social stressors, vaccination, immediate segregation and isolation of ill animals, all elements of good biosecurity.
Vaccination Matters
Broodmares should be vaccinated at 5, 7, and 9 months of gestation using a vaccine specifically labelled for abortion protection. Annual boosters for all horses on the property help reduce viral shedding and protect the herd.
Biosecurity Basics
Isolate new arrivals for at least 21 days.
Avoid mixing pregnant mares with young or traveling horses.
Monitor daily for fever or respiratory signs.
Minimize stress to reduce viral reactivation.
Disinfect equipment and avoid sharing tack or feed buckets.
Limit human transmission — wash hands and change clothes between groups.
If you suspect an outbreak, act fast: isolate affected horses, restrict movement, and use dedicated staff and gear for sick animals.
EHV-1 can linger silently in horses and re-emerge under stress. Staying ahead with proactive care keeps your mares—and foals—safe.
While EHV-1 is particularly serious in broodmares due to the risk of late-term abortion, any horse under stress: whether from travel, illness, competition, or environmental changes, can shed the virus. This shedding can occur even in horses that appear healthy, making them silent carriers and a potential source of infection for others in the herd. That’s why biosecurity and vaccination protocols are essential not just for pregnant mares, but for all horses on the property.
