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.

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 weeks.
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
Canal 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.

Treatment
Blood tests and nasal swabs are necessary for definitive diagnosis, but consistent clinical signs and close proximity to a confirmed property is often enough.
If you suspect your horse has equine flu, stop working him immediately. Continuing to work an affected horse will worsen their respiratory status.
The very young and the very old are most vulnerable due to reduced immune system. Aged horses and foals aged from one to five months can be affected by pneumonia, which can be fatal.
Keep sick horses out of bad weather and in the shade.
Treatment of equine flu boils down to rest and husbandry. There is no direct means of fighting the virus with drugs, and while anti-influenza compounds are available for use in humans, these have not been used extensively on horses.
Horses should be rested for one week for every week of fever, with a minimum of three week's rest. A veterinarian may prescribe an anti-inflammatory drug if the horse's fever is over 40ºC (104F). Antibiotics may be prescribed when the fever lasts for more than three or four days, or when purulent nasal discharge or pneumonia are present.¹
Fresh air and rest are vital. Avoid dust in the environment, bedding and feed (particularly hay) to minimise the risk of bacterial infections of the lungs and airways.
Affected horses should be confined, and walked for short periods to maintain circulation. This should continue for at least the period of the fever and coughing, followed by gradually increasing exercise.
The virus damages the respiratory tract, which is the lung tissue and windpipe. Secondary bacterial infection can result. It takes 30 days for repair of this tissue. For equine athletes, a subsequent 30 days is also advised before starting work again.