News Notes

Warn Owners About Expected Rise in EIV

As winter transitions to spring, warn owners and barn managers to be on alert for equine influenza (EIV).

The latest annual analysis from the Equine Bio-surveillance Program, a surveillance system managed by Merck Animal Health with the UC Davis, Equine Infectious Disease Research Laboratory, reveals that EIV remains a frequently diagnosed respiratory disease, alongside equine herpesvirus type 4 and Streptococcus equi subspecies equi. This trend aligns with the program’s cumulative findings spanning 17 years.

“Every year, we see an uptick in equine influenza cases as horses begin traveling for competitions and training in the spring,” said Duane E. Chappell, DVM, associate director of equine pharmacovigilance and professional services at Merck Animal Health. “The virus spreads rapidly through direct horse-to-horse contact, shared equipment, and even human handlers who inadvertently carry the virus among horses.”

Horses traveling for events are at increased risk. According to the latest biosurveillance update, 58% of horses diagnosed with EIV had a recent history of travel. Show horses were the most commonly affected group, accounting for 42% of cases.

“Young horses, those under stress from travel, and those in high-density environments like showgrounds are particularly vulnerable to equine influenza,” Dr. Chappell said.

Given the seasonal rise in cases, urge horse owners to take proactive steps to protect their animals. Key prevention measures include:

• Vaccination: Ensure horses, particularly if they travel, are up to date on their influenza vaccinations.
• Biosecurity: Limit direct contact with unfamiliar horses and avoid sharing tack, water buckets or grooming tools.
• Monitoring, quarantine: Monitor new arrivals or horses returning from events for at least 2 weeks before full herd integration. Daily temperature checks during travel can identify early signs.
• Hygiene practices: Handlers should wash hands (or use hand sanitizer) and disinfect equipment regularly. MeV