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Equine Health Resource

Equine Influenza, EI

Synonyms: Flu, Grippe, Stable Cough

Equine influenza is a highly contagious respiratory virus that affects a number of mammal species, including horses. Symptoms range from mild to severe. Flu commonly causes fever, coughing and nasal discharge. Younger horses tend to be more susceptible to the virus, which is transmitted via air-born secretions from coughing horses or contaminated tack and equipment.

Like many respiratory viruses, flu is usually self-limiting. Separation from other horses, rest and generalized supportive nursing care is often all that is necessary. However, some horses develop secondary bacterial infections, and even bacterial pneumonia can result. It is very important not to prematurely resume training or exercise.

Equine influenza (virus Type A) is a reportable disease, meaning that if a horse has or is suspected of having this disease, vets are required to report it to agricultural authorities (usually the State Veterinarian). These authorities may investigate the case as part of a larger effort to monitor equine health and coordinate with other states and the USDA APHIS in preventing the spread of illness or disease on a national and international level.

Diagnosis requires laboratory confirmation, usually PCR testing on respiratory secretions.

Treatment is supportive nursing care, and most importantly, isolation from other horses.


  • When can my horse resume forced exercise or work again?

    Several vaccinations per year may be recommended for horses at higher risk due to increased exposure at shows, racetracks or competitions. At our clinic, we recommendation vaccinating horses every 6 months, at minimum.

    Helpful Terms & Topics in HSVGWritten, Reviewed or Shared by Experts in Equine Health

    Helpful Outside ResourcesCredible Equine Health Information on the Internet

    Author: Doug Thal DVM Dipl. ABVP


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