Equine InfluenzaBy Kentucky Equine Research Staff · August 22, 2011
Influenza in horses is a viral respiratory tract infection that causes coughing, nasal discharge, and elevated body temperature. The disease is highly contagious, spreading rapidly through a boarding stable or racing barn where horses may come in contact with buckets, tack, or other surfaces contaminated by nasal secretions from sick animals. The disease can also be picked up when a horse inhales the virus spread by a coughing horse suffering from influenza. Though horses of any age can be infected, influenza is somewhat more common and often more severe in horses from one to five years old.
In addition to the more common signs, horses with influenza may show swelling of the lymph nodes under the jaw. Edema of the limbs and belly are seen in rare cases. If a bacterial infection follows influenza, pneumonia can develop. This may be the case if the thin, clear nasal discharge of influenza thickens and turns green or yellow.
Treatment for mild cases of influenza may consist only of rest (generally for several weeks) and nutritional support. Nonsteroidal anti-inflammatory drugs are used to reduce fever and discomfort. Antibiotics can be used to fight pneumonia if this develops.
Influenza is rarely fatal, but its impact can be significant because horses generally take at least three weeks to recover, and may take as long as three or four months to fully regain their health. Performance and training schedules must be put on hold until the horse is able to work again, so an entire season of work may be lost to severe cases of influenza.
Fortunately, a vaccine is available to protect horses from influenza. After establishing immunity with an initial series of three injections, horses are usually given semi-annual booster vaccinations. This protocol goes a long way toward preventing most horses from picking up the most common strains of influenza. However, various new or mutated strains show up from time to time, so management is an important part of preventing controlling influenza outbreaks.
Owners should check with their veterinarians as to which horses need to be vaccinated and how often they should get vaccinations. Retired horses that never leave the farm and belong to an established herd are at lower risk than animals that frequently travel, show, and meet other horses.
Newly arriving horses should be quarantined for 14 to 21 days after arriving at a farm before they are turned out with other horses. Minimizing shared buckets, tack, and grooming supplies will also help to avoid spreading disease to uninfected horses.
