Equine Flu

Equine Influenza (flu) is a disease that affects the upper and lower respiratory tract of horses, donkeys and mules. It is caused by several strains of the equine influenza virus. The disease is very infectious and spreads rapidly through groups of horses. The incubation period is 1 – 3 days.

Further Advice

Common Questions

What causes equine flu?

Equine flu is caused by a virus. Viruses are tiny infectious particles that can produce disease, although they can only replicate inside another cell. Once a horse has breathed in the virus, it invades the lining epithelium of the airway, which becomes swollen and inflamed producing a very sore throat and a nasty cough. The viral damage causes patches of the membranes lining the airways to ulcerate and these changes disrupt the clearance of mucus and other debris from the airways. In turn these damaged areas end up being invaded by bacteria and further infections ensue.

Antibiotics have no effect against a virus, but they can be useful to control secondary bacterial invasion. This is a particular risk in foals that can succumb to a fatal pneumonia.

What are the warning signs of equine flu?

A very high temperature of 39-41C (103-106F) which has lasted for 1-3 days
A frequent harsh, dry cough that can last for several weeks
Clear, watery nasal discharge that may become thick and yellow or green
Enlarged glands under the lower jaw
Clear discharge from the eyes
Depression and loss of appetite
Filling of the lower limbs

How can equine flu be prevented?

Vaccination has proven to be very successful in preventing outbreaks of Equine Flu – we always recommend vaccinations as an essential part of any proactive health plan.

How is a diagnosis made?

An accurate diagnosis can be made by

Recognising the clinical signs and the rapid spread between horses
Isolation of the virus from Nasopharyngeal swabs
A number of other laboratory tests which identify the virus
Rising antibody levels in blood (serum) samples taken early in the course of the disease and 2-3 weeks later
History of recent contact with a confirmed case of the disease

What should I do if I think my horse has equine flu?

As soon as a horse shows any suspect signs, strict hygiene and isolation procedures should be applied. Any horses that have been in contact with the affected horse should be carefully monitored
and should not attend shows or any other competitions as they may be incubating the disease.

Exposure to the virus combined with the stress of travelling will make infection more likely. The disease is spread by inhalation of virus released into the atmosphere as an aerosol by coughing and blowing, essentially one horse coughing over another. For this reason equine flu is highly contagious within a group of horses, but it is not airborne over long distances like some other viruses such as foot and mouth disease virus.

If you suspect your horse has equine influenza you should contact your vet. Steps can then be taken to stop the spread of the disease and manage the condition appropriately in each effected horse. One of the most crucial is identifying the infection accurately; if you know what you are dealing with, then you can control it.

How should I manage an animal with equine flu?

All horses with respiratory infections should be given complete rest. Ideally, they should not recommence any strenuous exercise until two weeks after the signs have gone. Treatment is given symptomatically, sometimes consisting of anti-inflamatory drugs. Antibiotics are not routinely effective in managing cases of Equine Flu, as it is cause by a virus, not a bacterial infection. However, secondary bacterial infection can occur, leading to conditions such as bronchitis and bacterial pneumonia. In these cases, antibiotics can be used.

Frequently the advice is given that they should have a week off for every day that they have had a fever (raised temperature), but many riders will find the their horses are below par for longer, in
the same way the people can feel run down after flu. Good stable ventilation and management is essential. Exposure to dust and spores should be minimized as horses with respiratory infections
are susceptible to developing recurrent airway obstruction (RAO).

If hay is fed, it should be of good quality and soaked. If weather conditions permit, affected horses benefit from being turned out into a small paddock for at least part of the day once their temperatures have returned to normal. This is especially important in the recovery stages. Some of the new antioxidant feed supplements market to help respiratory function may well be of benefit as well as some other medications to help breathing.

In all cases, we will give you specific advice depending on the case itself.