Equine Influenza

Equine Influenza Q & A’s

What is equine influenza and how does it spread?

It’s a respiratory disease which affects Equidae – horses, donkeys and mules. It’s not usually fatal, but
horses may contract the likes of pneumonia and other serious complications as a result. It’s spread
through nasal discharge, and the coughing and snorting that go with most chest infections. It is highly
contagious. The reactions of horses vary widely. Some develop only a fever and a cough, while others
get very sick. It may take a horse a few months to completely recover to full fitness.

Why such big concern about its spread?

In countries such as New Zealand and Australia, which haven’t had the disease, there will be no
resistance in the local equine population. That means it will spread very quickly and many horses will
catch it. The recovery time will create huge disruption to all equine-related sports. Interestingly, since
the Australian outbreak in August 2007, New Zealand is the only country left with a major equine
population that remains free of the disease in its general population. While most horses get over the
disease, veterinarians report more post-infection problems with equine flu than with most other
respiratory infections. Heart problems and pneumonia, for example, are not uncommon.

Does it have an incubation period?

EI is transmitted directly from acutely infected horses to susceptible horses. Horses with the disease
remain infectious for up to seven to 10 days. The dry, harsh-sounding cough may linger for several
The disease has a very short incubation period (time from infection to symptoms) of two to six days
and clinical signs usually resolve in one to three weeks.

How long is an infected horse contagious?

About 15 days.

What does the virus do?

It attacks the airway lining, which becomes inflamed and can ulcerate. The animals gets a sore throat
and cough as a result. They have trouble clearing mucus from their airways, and areas of damage
resulting from the infection are more prone to bacteria infections.

What are all the symptoms?

A high temperature of 39-41deg C (103-106deg F), lasting for one to five days. A dry, harsh-sounding
cough that may linger for several weeks. Some horses may cough only two or three times a day, but
others more frequently. Coughing is generally worse when eating hay or hard feed. Nearly all horses
will develop a clear, watery nasal discharge that may turn green or yellow as secondary infections
developed. Swollen lymph nodes under the jaw, a clear eye discharge, depression, lethargy, loss of
appetite. There may be swelling in the lower limbs. Animals are often depressed, off their food, are
stiff and reluctant to move. Other signs include runny nose and eyes. Pneumonia may develop in the
very young and very old. This may be fatal in a few cases.

How long does recovery take?

Horses suffering from equine influenza should be given complete rest. As a general rule horses should
have a week of complete rest for every day they have a raised temperature. Generally horses require
at least 30 days complete rest after infection, or longer if they suffer a fever for more than 4 days. Like
people with influenza, individual horses recover at different rates. After about 30 days of complete
rest, only light exercise is recommended for a further 30 days, then fitness should be built up by
gradually increasing work.

Can people catch it?

No. But they can transfer it from one horse to another, on their hands or their clothing. Mostly, you
would expect the disease to spread from just coughing. Once exposed to the virus, a horse is likely to
come down with the flu in about three days.

How long does the virus live for?

On hard, non-porous surfaces like plastic: 24-48 hours. Cloth and paper: 8-12 hours. CCanal water: up
to 18 days. Thorough cleaning with soap or detergent and water and disinfectant easily kills the virus.

How do I decontaminate myself?

EI is a fragile virus and is easily killed. Simply soap and water or detergents will kill the virus. If in
contact with a suspicious horse, it is recommended that you change clothes and boots, shower with
soap, and shampoo hair. Avoid contact with horses for 48 hours.

How do I decontaminate my equipment and vehicles? 

Thorough cleaning with soap or detergent and water and disinfectant can easily kill the virus. The virus
is killed by exposure to sunlight for 30 minutes.

Is there a carrier status?

Horses who recover will not infect other horses.

Will my horse become infected again?

Infection with this strain of EI will result in immunity, although not for life. Therefore, if challenged again
by the same virus in the near future your horse will not redevelop the disease

What is the recovery period?

It is suggested that it takes 30 days for repair of this tissue. For equine athletes, a subsequent 30 days
is also advised prior to the recommencement of work.

Is there a vaccination available?

Yes. In countries where the flu is present, many horses are vaccinated annually. Vaccinated horses
can still show symptoms, which these will be much milder than unvaccinated horses.

Are there side effects with vaccination?

There can be. Side effects can include:

• A transient swelling (max. diameter 5cm) which regresses within 4 days may appear at the
injection site.
• Pain and local hyperthermia can occur in rare cases.
• A slight increase in temperature (max 1.5C) may occur for one (1) day, exceptionally two (2) days.
• In exceptional circumstances, apathy and reduced appetite may be observed the day after
• In exceptional circumstances a hypersensitivity reaction may occur, which may require appropriate
symptomatic treatment.


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