While it’s widely hypothesized that horses shed equine herpesvirus-1 (EHV-1) during times of stress and illness, researchers on a new study say that critically ill horses with acute gastrointestinal disease (colic or colitis) in a veterinary hospital do not appear to shed the virus.

According to Elizabeth Carr, DVM, PhD, Dipl. ACVIM, ACVECC, assistant professor in Michigan State University’s Department of Large Animal Clinical Sciences at the College of Veterinary Medicine, EHV-1 is an important infectious disease in horses that can cause outbreaks of disease both on farms and in hospitals. Veterinarians seem to be diagnosing it more frequently.

"Once horses are infected, the virus lies dormant and can recrudesce (become active again) at any given point," explained Carr. "To date, the triggers that cause nasal shedding of EHV-1 remain unclear."

To assess the impact of stress and disease on nasal shedding of EHV-1, Carr and colleagues evaluated 122 hospitalized, critically ill horses older than six months of age. They tested horses’ blood samples and nasal secretions for EHV-1 using a polymerase chain reaction test (a DNA test)