Equine influenza isn’t the most dangerous disease your horse might encounter. Most horses recover fully from this viral respiratory infection with little more than rest and supportive care.

Still, influenza can be a real nuisance. It’s highly contagious; the virus easily spreads from contact with contaminated surfaces and via airborne droplets exhaled by an infected horse. The incubation period for equine influenza is just a day or two, so an entire herd of horses can be feverish and coughing before you notice the first one is sick. And the recovery period—a minimum of three weeks—can put a serious dent in your riding and training schedule.

Younger horses, between the ages of 1 and 5 years, who haven’t been exposed to the virus are the most susceptible to equine influenza, but recent surveys have found that increasing numbers of mature horses are also falling ill with this disease. Other populations at greater risk for influenza include horses who travel frequently to shows and competitions. Not only do the stresses of travel and intense training make a horse more susceptible to any pathogen, he is also more likely to encounter the influenza virus at venues where there are many horses.

The good news is that several vaccines are available that are effective against equine influenza, and these, combined with commonsense hygiene measures, can go a long way toward keeping your horse healthy. Here’s what you need to know.

Preventive measures

The American Association of Equine Practitioners lists equine influenza among risk-based vaccinations, which are recommended for horses deemed to be more likely to come in contact with the disease. Currently, three general types of equine influenza vaccine are available: inactivated (killed virus), modified live virus (MLV) and recombinant (canary pox vector). All of these vaccines have benefits and drawbacks. Some, for example, are more appropriate for pregnant mares, and some confer protection against infection more quickly. Your veterinarian can help you choose the product and schedule that is best suited for your horse.

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In addition to vaccination, it’s a good idea to take basic precautions to limit your horse’s exposure to the virus through good biosecurity:

• Reduce contact with unfamiliar horses. Not only can nose-to-nose “greetings” lead to squealing and nipping, it can allow viruses to pass from horse to horse. Not all contagious horses look or act sick, so unless you have information about a horse’s vaccination status and recent health history, it’s impossible to know if he poses a disease threat.

• Do not share equipment. The influenza virus can survive on surfaces, such as tack and brushes, for several hours, possibly even days. Use your own equipment when you’re away from home, and if you must share an item, clean it first with a disinfecting soap or wipe before using it on your horse.

• Avoid communal water troughs or buckets. The influenza virus can survive in water for hours or days. Shared water is OK at home when you know the health status of your herd, but bring your own buckets to shows and trailheads, and keep your horse away from public troughs.

• Segregate travelers from horses who stay at home. Horses who often go to shows and clinics are more likely to pick up influenza or other illnesses. It’s a good idea to keep them separated from horses who never leave the farm, especially pregnant mares and foals, for at least a week after they return.

• Quarantine new horses. Ideally, you’d have a separate turnout to keep a new horse separated for at least two weeks, long enough for him to show signs of any developing illnesses. If that’s not possible, consider alternating turnouts, putting the new horse out while the others are in the barn, and vice versa. Another alternative is to cordon off a portion of the existing pasture with temporary fencing; you’ll want to create a double fence, with about 10 feet in between, to prevent the horses from reaching over and touching noses.

• Keep clean. Remember that viruses can pass from horse to horse on your hands and clothing as well as on tools and equipment. It’s a good idea to wash your hands with soap after handling each horse in your care and dedicate a set of tools to use only with a sick horse. You might also consider keeping dispensers of hand sanitizers in your barn where you can reach them conveniently when needed.

Caring for a horse with influenza

A fever—as high as 106 degrees or more—is one of the earliest signs of equine influenza. The horse will also likely be lethargic and not eating. Other signs may include a clear discharge from the nose, coughing and enlarged lymph nodes under the jaw.

If you suspect your horse is ill, isolate him from the rest of the herd. Move him into a separate paddock, or place him in a stall at the end of the aisle, away from the activity in the barn. Place fans to direct airflow from the stall outward, through a door or window, rather than toward other stalls.

Also check the other horses for developing fevers. Ideally, you’d ask someone who hasn’t touched the sick horse to tend to the others, but if you’re the only one available, finish taking care of the patient first, then wash up and, if possible, change your clothes before moving on to other horses.

There is no specific treatment for influenza beyond rest and supportive care while the infection runs its course—usually three days or less. Your veterinarian may prescribe anti-inflammatory medications to curb the horse’s fever, which will make him more comfortable so he will continue to eat and drink.

The problems caused by influenza do not end after the initial infection subsides. The virus damages the cilia, the hairlike appendages that line the trachea and help keep the airways clear of inhaled dust and debris. Until the damaged airways heal, the horse will be vulnerable to secondary bacterial infections, characterized by a thicker yellow/white nasal discharge. In a worst-case scenario, the infection may progress into pneumonia.

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To reduce the risk of secondary infections, keep the horse in a clean environment while the cilia are healing. The general rule is to allow at least three weeks of rest, or a minimum of one week of rest for each day that the horse had a fever. Even light riding too soon increases the risk that a horse will become sick again.

After your horse recovers, clean up his environment and tools you used to care for him. Soap and water is probably adequate but bleach or stronger disinfectants will sterilize items. In addition to spraying down stall walls and scrubbing mats, clean water and feed buckets, grooming tools, halters and any other tools or equipment that came in contact with the horse while he was sick. Laying freshly cleaned items in direct sunshine to dry will give them an extra boost of disinfection from the sun’s ultraviolet light.

This article first appeared in the December 2017 issue of EQUUS (Volume #483)

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