Here are answers to some of the most frequently asked questions about equine influenza.

Note: For medical concerns regarding your horse's health, please consult your veterinarian. Please do not send us specific queries about clinical symptoms your horse is experiencing as we are unable to address such questions.

Q: What causes equine influenza?

Equine influenza is a viral disease caused by viruses closely related to those that cause flu in people. Two subtypes of influenza A virus are known to cause influenza in horses, these are the subtypes H7N7 (formerly known as A/equine 1) and H3N8 (formerly known as A/equine 2).

Q: What are the signs of equine influenza?

Equine influenza appears similar to a range of other viral respiratory diseases including equine herpesvirus, equine rhinovirus and equine adenovirus. Most of these viruses produce rather mild sings which include a runny nose and coughing. Particularly in susceptible animals, equine influenza produces more severe symptoms with horses developing a fever (body temperature of 38.9degC or 102degF or more) and a dry hacking cough. Horses frequently become depressed and reluctant to eat or drink for several days but usually recover in 2 to 3 weeks.

Q: How is influenza virus spread?

The virus can be spread easily from horse to horse as a result of droplets released into the air by coughing and also from nasal discharge and from things like infected brushes and rugs. The disease is very contagious and there is almost 100% infection rate in an unvaccinated population that has been previously unexposed to the virus.

Q: What is the incubation time?

Most horses exposed to the virus will show signs within a period of one to 5 days.

Q: How is equine influenza diagnosed?

Occurrence of a rapidly spreading respiratory infection in a group of horses characterised by rapid onset, high fever, depression, weakness and widespread coughing is usually sufficient to make a presumptive diagnosis of equine influenza. However, because it can be difficult to distinguish from other respiratory infections on the basis of clinical signs alone, laboratory assistance is usually required for a definitive diagnosis. Confirmation is based on detection of virus in nasopharyngeal swabs, which should be taken as soon as possible after the onset of illness, or serology of acute and convalescent sera. In the past, detection of virus in nasopharyngeal swabs relied on being able to grow the virus in embryonated hens' eggs, which takes a minimum of 3 days. Nowadays, rapid tests are available for detecting virus in nasal secretions and same-day results can be obtained.

Q: Can equine influenza be treated?

Mildly affected horses recover uneventfully in 2 to 3 weeks and horses that do not develop complications require only rest and good nursing. Rest should be complete and for a sufficient time after clinical signs have gone to prevent long-term lung or myocardial damage. Antipyretics are recommended for horses with a fever of more than 40.5degC (105degF). There are no drugs that can influence the outcome of the disease licensed for use in horses. However, damage to the respiratory tract epithelium means that many horses develop secondary bacterial infections, which can lead to pneumonia and other problems. Treatment with antibiotics to lessen the impact of secondary infections is recommended when fever persists beyond 3 to 4 days or when purulent (snotty) nasal discharges or pulmonary involvement are present.

Q: How can equine influenza be controlled?

Control of equine influenza requires sound management and use of vaccination. The likelihood of exposure to infection can be reduced by isolating any horses newly introduced into a stable or group of horses and by minimising contact with other horses. In most countries, racing and other equine authorities require that horses be vaccinated prior to taking part in competitions.

Q: Can vaccination give my horse flu?

Most licensed flu vaccines are made from inactivated or killed flu viruses and cannot cause the flu or flu-like illness.

Q: Do equine influenza vaccines work?

The duration of protection provided by current vaccines is limited but provided that booster vaccinations are administered and the viruses in the vaccine and circulating viruses are similar, vaccination is very effective.

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