Managing the Horse with Heaves

By Heather Smith Thomas

Some horses suffer impaired respiratory function due to congestion and constriction of the airways—similar to a person with asthma. This condition is generally the result of breathing dust containing mold particles, or pollens, and is often due to the conditions in which we keep and feed our horses.

Horses are super athletes, primarily because they have good lung capacity for keeping the blood and muscles well supplied with oxygen during strenuous activity. Anything that interferes with proper working of the lungs and air passages can limit a horse’s athletic ability. If a horse tends to suffer bouts of impaired lung function, the environment and management of that horse needs some changes.

Amy Johnson DVM, DACVIM (Large Animal Internal Medicine, New Bolton Center in Pennsylvania) says the most important treatment is environmental and dietary management changes to reduce the horse’s exposure to the triggers for this disease. “The triggers are usually dust, molds and endotoxins found in hay and straw in a barn environment. We tell owners that the ideal situation is usually to have the horse out on pasture 24/7. If that’s not possible, then the horse should be in a stall that has the least exposure to these particles in the air the horse is breathing,” she says.

A corner stall by a window might be better than a stall in the middle of the barn. “Make sure that the most air flow is away from any storage stall or area where bales of straw or hay might be located. The worst barns are the ones with overhead hayloft, with particles raining down from the ceiling,” says Johnson.

Barn stalls adjacent to an indoor arena will also be dusty if they share the same air space. “When horses are being exercised they are churning up dust. If the heavey horse has to be in a barn, it should be one with minimal dust. If the horse has to be in a barn part of the day, don’t have that horse in the barn when the stalls are being cleaned or people are blowing or sweeping the aisles. Even if the other horses are in the barn while it’s being cleaned, make sure the heavey horse is not in the barn,” she says.

“If the horse is outside and being fed hay, make sure it’s not big round bales. Those have higher levels of endotoxin/dust/mold compared to other forage sources. People think that the horse will be fine just because it is outside, on pasture, and then wonder why the horse isn’t getting better—and it’s because the horse is sticking its nose into a round bale and breathing the dust,” she explains.

Feeding is an important issue, paying attention to the dust levels in feed. “It’s really a spectrum; some of the mildly affected horses, as long as they are outside can tolerate hay. Other horses may not be able to tolerate dry hay, but if you wet the hay (by sprinkling it or soaking to reduce the amount of particulates they are inhaling) can still be fed hay. A few, however, still inhale enough particles/allergens from wet hay to trigger the disease, and have to be taken off hay. They need to be fed a complete pelleted ration or cubes instead of hay.” In severe cases it also helps to moisten the cubes or pellets.

“Regarding bedding, straw is probably the worst choice for these horses. It pays to try to find a low-dust bedding. We use chopped paper or cardboard bedding at our hospital for these horses. Sawdust is also better than straw. Some people wet down the fresh bedding a little bit to reduce the dust before they put the horse back into the stall. Pellets over stall mats also work pretty well for a low-dust bedding,” she says.

MEDICATION – If a horse suffers an episode of heaves, and has trouble breathing, medication is necessary to reduce the inflammation and bring him back to a comfort level where he isn’t struggling to breathe. “The medications we usually recommend for an acute crisis would be systemic steroids (dexamethasone or prednisolone) administered either IV or in the muscle, or even orally, and bronchodilators,” says Johnson.

This disease involves both inflammation and constriction of the airways. “You need to get rid of the inflammation with the steroids, and then you need to treat with a bronchodilator to open the air passages that are squeezed shut. Probably the best course is to use one of the aerosolized bronchodilators, such as an inhaler. They seem to work more quickly than the oral medication (clenbuterol, which is marketed as Ventipulmin). An aerosolized bronchodilator has been shown to improve lung function significantly within about 5 minutes, and the oral drugs can’t act that quickly.”

“In the long term, if you have a horse than needs more than just environmental changes, we suggest that owners use an aerosolized medication as a maintenance therapy. This reduces the systemic side effects that can be a problem when keeping a horse on a systemic steroid. There are several options such as the Flexineb and EquiResp,” she says.

“This involves a big up-front cost because these are not cheap, but in the long term the horses benefit enough that it is worthwhile for many owners if they can get out there and medicate the horses. Most horses tolerate these devices pretty well, but once in a while we find one that wants nothing to do with it.” Owners have to figure out what works and what is workable for each individual horse.

“Owners need to understand from the beginning that this is not a condition that you treat and it goes away and you never have to think about it again. This is a lifelong problem, caring for that horse. The horse may be useful and continue a performance career for many years, but will not be able to go back to the management situation or conditions in which it started showing signs.” The owner must continue with the environmental changes and altered management, to keep the horse breathing normally.

“There are many horses that have no clinical signs—that once they get out on pasture and away from the dust of a barn and hay they don’t need any drugs for years and years. They are fine as long as they stay away from allergens in the hay/dust,” she says. But if you bring them back into a barn or an area where dust particles are floating around in the air, they will be coughing and wheezing again.

“As far as diseases go, this one is fairly easy to deal with because even though we don’t yet fully understand everything about why it happens, at least the treatment and management protocols have been fairly well established. We know what works, and everyone agrees on it. It’s not a controversial disease regarding the treatment and management of these horses,” says Johnson. We know about the triggers, and we know that we can treat a horse when it has a breathing crisis and needs help.