Fresh air is crucial to a horse's respiratory health. Photo © EQUUS magazine
Q: My gelding was diagnosed with seasonal asthma. In the spring and fall, he coughs and is easily winded after trail rides. We currently have him on albuterol, but since he's still symptomatic, our veterinarian suggests we change his medication to a more potent bronchodilator or an inhaled cortico-steroid. He spends some time each day in a stall, but I'm considering switching him to complete field board to see if that helps. Is there anything else I can do, either medically or management-related, to ease his signs?
A: Respiratory allergies are a common problem in horses. They often begin as a simple cough at the start of a workout. Over time, the condition may progress to where the horse has difficulties breathing and in severe cases can be life threatening. Previously known as heaves or COPD, recurrent airway obstruction (RAO) is an inflammatory and constrictive disease of the lower airways in the lung. Left untreated, your horse's quality of life and ability to perform can be seriously affected on and off the trails.
There are several steps you can take to get your horse to tolt with gusto again. Managing your horse's environment can have a big impact on his ability to breathe. Start by trying to identify what substances bother him, such as pollens, dust or molds (a.k.a. allergens). Keep in mind your horse might be sensitive to multiple allergens. A bit of detective work and experimentation will be needed. Monitor your horse closely and take note of when his signs seem to get worse (after a night inside a stall, for example, or after a ride in the woods versus around the ring or pasture). You might want to get a notebook and keep track of your observations so you can notice patterns over time. Since your horse's allergy is seasonal, you can narrow your search to allergens found only in the spring and fall.
Once you've determined which conditions seem to trigger allergic responses, make changes accordingly. If he's worse after being indoors, clean the barn, improve the ventilation and keep him out as much as possible. If he's worse when he's outside, try changing the time of day he's turned out.
You can also have skin or blood tests done to help narrow your search. These tests look for the body's response to common allergens. If there is a heightened reaction, the horse may be allergic to that substance. Both forms of testing have been shown to have accuracy problems with respiratory allergens, but they may still be useful if interpreted carefully by your veterinarian.
No matter what sensitivities you find, remember that dusts and molds often irritate horses with allergies. Avoid dusty rings, round bales, hay, grain, supplements and bedding. I often see a good improvement in horses if we soak their hay in water for 15 to 20 minutes before feeding. Many horses do even better if we remove all hay and offer a complete feed.
Now let's talk about medical management. The medical plan revolves around what changes are happening in the lungs. The first priority is to decrease the inflammation in the airways. This is usually accomplished with potent anti-inflammatories called corticosteroids. Dexamethasone and prednisolone are two that are commonly used.
Oral steroids can be an effective and inexpensive way to control RAO. But be aware that corticosteroids taken orally or by injection can potentially have serious side effects, such as laminitis and an increased susceptibility to infections. I am very cautious about using them in horses with Cushing's disease or who are otherwise prone to laminitis. That said, I have found that very low doses seem to be effective and may be an option during the worst times of year.
I see you are considering an inhaled corticosteroid. This is a great idea in theory, because the drug is delivered directly to the airways and spares the rest of the body of side effects. The downsides are the expense and the challenge of drug administration. But I have had a handful of clients use them in the inhaled form with good results.
The second issue I will address is bronchoconstriction, or narrowing of the airways. This problem is common with RAO and makes it difficult for the horse to breathe. Bronchodilator drugs such as albuterol and clen-buterol relax the muscle that constricts the airways. Albuterol, effective in an inhaled form, can provide immediate relief but has a short duration and requires a special device to deliver the drug. Clenbuterol comes as an oral liquid. It lasts longer but can occasionally have significant side effects, is fairly expensive, and its effectiveness may diminish over time.
Corticosteroids and bronchodi-lators can work well managing RAO. But there are approaches that can be used complementary to or instead of medical therapy. The most effective I have found is desensitization (allergy shots). With this approach we attempt to "trick" the immune system into forgetting about the offending allergens. This is done by administering a series of injections that contain very low amounts of the allergen to which your horse is sensitive. Over time, the amount of allergen is slowly increased until the immune system ignores them.
I found that the majority of horses I've worked on have responded favorably to this approach. Desensitization is a good option when medical management is only partially effective or cannot be administered safely, or if clients prefer a more holistic approach. In addition, holistic veterinarians have successfully used complementary medicine, such as acupuncture, to improve horses with allergies by modifying the body's immune system. The goal is to bring the body's immune system back into balance.
Finally, if he does not appear to respond well to any of the therapies, a re-evaluation is always advised. As with all medical advice, it is best to talk with your veterinarian about what is right for you and your horse.
David Trachtenberg, DVM
Trachtenberg Veterinary Associates
Penfield, New York
This article first appeared in EQUUS issue #430.