Equine Influenza Diagnosis

Easily one of the most highly infectious upper respiratory conditions among the equine world, influenza is responsible for much economic loss through veterinary costs, training time and productivity. Vaccines attempt to control outbreaks but variations in the virus and its ability to be transmitted through surfaces, make it not easily managed. Once diagnosed, isolation and good sanitary procedures are often the best defense against the virus and the possibility of more serious complications.

  1. Equine Influenza

    • Equine Influenza is highly contagious, often affecting entire herds to varying degrees. The virus is transmitted via airborne particles or by sharing of utensils such as buckets or grooming equipment and has a short incubation period of one to five days. The virus can live on clothing, feed, grooming equipment, trailers and other surfaces for two to three days and horses can remain infectious three to six days after the last symptoms are apparent.

    Symptoms

    • Clinical signs include high fever (exceeding 106 degrees), coughing, and nasal discharge. Some swelling of the lymph nodes may also be present. A secondary bacterial infection might occur in some horses, leading to pneumonia; in those cases, the nasal discharge will change from a clear, yellowish fluid to a thick green and yellow mucous.

      Most horses affected are between the ages of two and three, who have not been exposed to the virus and may be under stress from traveling, mixing with horses from different areas of the country, changes in diet and training.

    Diagnosis

    • Clinical signs of influenza are shared with other upper respiratory infections including equine herpesvirus-1 and -4, rhinovirus, streptococcus infection, bacterial pneumonia and strangles.

      Diagnosis is usually made from history and clinical signs as it is not always necessary from a treatment standpoint to know the exact cause of an upper respiratory viral infection past ruling out more serious causes. However, obtaining an accurate diagnosis is important for determining the efficiency of vaccines and thus, the health of the industry. A more accurate diagnosis can be made by swabbing the nasal passages and the sample put under a microscope to isolate the virus.

    Treatment

    • Horses diagnosed with influenza should be isolated and the virus allowed to run its course, usually within three to four weeks. Fevers that persist more than three days could be indicative of a follow-up bacterial infection such as pneumonia, and if confirmed, treated with antibiotics.

    Prevention

    • The American Association of Equine Practitioners recommends semi-annual vaccines for horses that have already received the initial series of three boosters. Age, broodmare status, current vaccine status and risk of exposure play important roles in determining how best to handle prevention as well as diagnosing the illness.

      Isolation of infected horses and good sanitation practices can help minimize the spread of the disease.