Horses with equine influenza should be isolated and kept at a minimum distance of 50 yards from other healthy equine residents. | Photo: iStock

Although vaccination plays an important role, it should not be relied on as the sole preventive measure. Similar to other influenza viruses, equine influenza virus mutates over time and vaccines must be periodically updated to keep current with circulating viruses.

Horses that have been vaccinated according to with manufacturer’s label instructions and the American Association of Equine Practitioners’ vaccination guidelines can be protected against equine influenza. Studies suggest that using the modified live intranasal (administered through the nose) vaccine in previously unvaccinated horses can provide protection within five days of the first administration. However, no vaccine is 100% effective. Investigations into recent cases indicate that vaccinated horses can develop mild clinical signs for a short duration, whereas their unvaccinated counterparts are more severely affected and more likely to develop secondary pneumonia and pleuritis (inflammation of the pleura, the thin transparent membrane covering the lungs and lining the chest cavity).

Implementing biosecurity measures is essential to protecting horse health during influenza season. Because influenza virus is spread most readily through nose-to-nose contact, it is critical to limit horse-to-horse contact and require strict isolation of new arrivals and sick horses. Infected animals should be kept at a minimum distance of 50 yards from healthy horses