Equine influenza is the most common respiratory disease in horses. We saw just how powerful the influenza virus can be when in 2007 an outbreak in Australia infected approximately 70,000 horses, costing the country nearly $100 million and halting equine activities. Australia historically had been influenza-free, so the horse population was not vaccinated against the disease–and it spread like wildfire.
It is always wise to be on the lookout for clinical signs of equine influenza and be proactive about preventing it. Luckily, the equine form of this virus has not changed or mutated very often, but researchers use these lulls in virus shift to research vaccine technologies and learn more about the virus and how it develops and responds to the immune system. Because influenza is such a fast-spreading virus, researchers want to be ready for when the next great mutation comes along.
Influenza is known as a "hit and run" virus. It hits hard and spreads very quickly via aerosol transmission, often leaving many damaged horses in its wake. Horses spread the disease every time they cough or sneeze, and the virus particles have been known to travel surprising distances (as much as 150 feet, according to the American Association of Equine Practitioners). Clinical signs often include high fever typically lasting three to four days, a dry, hacking cough, loss of appetite, muscle soreness, and nasal discharge.
Influenza damages protective epithelial cells in the respiratory tract linin