Influenza in Horses

Equine influenza is a highly contagious upper respiratory tract infection caused by strains of the influenza virus type A. The common type of influenza A virus that currently circulates in horse populations is the subtype A2 (H3N8). An earlier subtype, A1 (H7N7) is now believed to be extinct in horses and is no longer recommended for equine influenza vaccines.

 Like other respiratory diseases of horses, influenza is a source of major economic loss to the equine industry due to lost training days and veterinary costs. Horses become infected by inhaling the influenza A virus that is shed by infected, coughing horses or via equipment such as feed buckets, tack, and grooming aids that were contaminated by an infected horse.