Heaves goes by a new name these days — chronic obstructive pulmonary disease or COPD. New name; same old disease.
“Heaves” is one of the more descriptive names given to an equine disease. It reflects how the horse’s sides and chest must work and heave to try to get enough air into and out of the body. Like “strangles,” it immediately paints a vivid picture of the condition of the horse when in the throes of an attack. The lining of the nasal passages is often bright red. The horse is, literally, air hungry.
Also obvious in advanced cases is the “heave line,” which is a muscular indentation running along the outline of the rib cage and curving up into the flank along the last rib. It is caused by the horse forcibly using his diaphragm and abdominal muscles to expel air. It is most obvious during an ”attack” but can be seen in advanced cases when the horse is breathing fairly comfortably.
The list of symptoms is rounded out by coughing, which may also be present between attacks, and wheezing. In some cases, the wheezing is audible when standing near the horse; in others it can be heard with a stethoscope. As you may imagine, these horses have decreased exercise tolerance. They tire more easily, cough during and after exercise and take much longer to cool out/stop blowing after exercise.
With advanced COPD, the symptoms are so dramatic and the horse in so much distress he will need emergency attention. Changes earlier on are more subtle and insidious, waxing and waning until there are irreversible changes in the lungs.
Causes Of COPD
The progression of COPD is most similar to what happens to a person who has been a heavy smoker for years. The late stages of COPD are equivalent to emphysema in humans.
The roots of COPD may date back to an early age. At birth, the foal’s lungs are normal. With each breath, he begins exposing them to a wide variety of bacteria, viruses, yeast, fungi and other irritants in the environment. Normally, the defense mechanisms of the respiratory tract effectively filter out many of these, while surface mucoproteins protect the cells from the remainder.
One theory of how COPD may get started is that hypersensitivities develop to common irritants in the environment that would not otherwise cause any signs of disease or distress. This can happen when a foal has a viral or respiratory disease.
When the respiratory tract is actively fighting an infection, its defenses in general are stressed. Any breakdown in the normal protective mechanisms will allow irritants or potential allergens to get in direct contact with the lung tissues, even gain access to the blood stream. Once the horse develops an immune response to an irritant/allergen, the stage is set for COPD.
It is believed that COPD can develop in older horses following infections, with much the same mechanisms. Heredity plays a role in other species, but this has not been documented in horses as yet. Also, chronic exposure to dust, molds and fungi in hays and straws, as well as chemical irritants, can set the stage for COPD. Organic dusts and antigens from hays and grains you would not even be aware of under normal circumstances have been proven to cause respiratory reactions in horses. Ammonia and industrial pollutants in the air are also strongly suspected. Even manure may be involved.
Stages Of COPD
COPD develops over a number of years, during which the lungs go through a series of pathological, increasingly serious changes.
Early cases are most likely associated with a bronchitis or bronchiolitis. Symptoms are usually confined to a mild-to-moderate degree of exercise-related problems — the horse blows longer than normal after work, may cough during or after work, does not progress as well as expected in rigorous training, etc. We would not say a horse has heaves at this point, but he is clearly abnormal.
Examination of the chest by a stethoscope may detect no specific abnormalities, but veterinarians experienced with lung-related performance problems will often report that lung sounds are louder than normal, even at rest. Once the disease has reached a level that can be considered “moderate,” there will probably be lung-sound changes that indicate there is more mucus present in the lungs than is normal.
As the mucus builds and chronic irritation continues, inflammation in the walls of the airways causes them to become thickened, further reducing the diameter available for air flow, and weakening the walls. When this happens, they are more difficult to force open on inspiration and may become completely collapsed when the horse attempts to exhale. As a result, the “bad” air is trapped inside the lung and the oxygen in the pure “good” air will be diluted by this retained air. The retained air also over-inflates the lungs and can lead to rupture of the walls of the tiny air sacs — the alveoli — where gas exchange (oxygen in and carbon dioxide out) occurs. This final stage is emphysema.
A horse is diagnosed as having heaves once the damage to the bronchial walls starts to occur. By this time, the horse will probably have a higher than normal respiratory rate at rest, may have developed a larger chest diameter, has obvious trouble breathing when he exercises and is probably coughing a lot more. While never “normal,” this horse may have good and bad periods. Flare-ups can usually be traced back to an obvious precipitant — load of dusty bedding or feed, prolonged period in the barn, warm and humid or very cold weather.
In the terminal stages, the horse has difficulty getting enough oxygen to even move around. His response to treatment even with powerful drugs becomes less and less until euthanasia is the only option — but early diagnosis and proper management can make a huge difference in avoiding this horrible final stage.
Treatment Of Heaves
Managing heaves is similar to avoiding it — good management (see sidebar). Some horses may achieve additional benefit from cubed hay or complete feeds with a beet-pulp base.
Although some horses may have more trouble breathing in cold air, this is usually restricted to extreme temperatures and exercise in the cold. More horses can be expected to have trouble in hot, humid air because the high humidity is associated with a higher concentration of irritants and allergens in the air.
Do not use vaporizers on horses with chronic lung disease. Only true nebulizers (see sidebar) are likely to benefit horses with COPD. However, some pieces of equipment mimic real nebulizers. Clear any such therapy with your veterinarian before you use it.
Medications For Early Cases: Horses with mild chronic lung disease will often respond quite well to non-prescription medications. Something as simple as camphorated rubs/cream, such as Vicks VapoRub, may offer noticeable improvement.
There are also a variety of mentholated/camphorated breathing medications in liquid and paste form. These help some horses but not all and may not be of any more benefit than application of a rub to the nostrils. If you try an oral medication, use it 20 minutes to an hour before exercise (follow label directions).
Two we especially like are Wind-Aid (Hawthorne) and Resprun (Uckele Animal Health). Major active ingredients in Wind-Aid are menthol, eucalyptus and camphor with a thick vehicle that helps coat the throat. The Resprun formula also contains aromatic oils, such as orange and clove, that make it palatable and soothe the respiratory tract.
We also like the herbal product Cough Free (Sure Nutrition). This gives improved ease of breathing in many horses with low-grade chronic respiratory problems.
As with many herbal products, some horses may object to the smell. Mixing the product in a small amount of vegetable oil then working the mixture thoroughly throughout the feed will help.
If the horse has problems related to increased mucus in the lungs , your veterinarian may recommend a potassium or sodium iodide supplement. This encourages secretion of the bronchial glands with more watery secretions that are easier to move out of the lung.
Nutritional support can also help alleviate the mild symptoms and decreased exercise tolerance. Vitamin C is extremely important to the health of the lungs and of much potential benefit to these horses when given at a rate of from 4.5 grams to 7.0 grams a day. You can use either a pure C product, such as Pure C (Vita Flex), or a wider spectrum antioxidant product such as Anti-Oxidant Concentrate (Vita-Key) or Nutragard (Vita Flex). Both contain other antioxidants well as trace minerals important for maximum antioxidant enzyme function.
Nutragard has the advantage in that it contains bioflavinoids, including hesperidin, which many veterinarians report are beneficial for respiratory problems. However, the vitamin C level is on the low side, so you should supplement this product with Pure C. An alternative is to use Vita-Key’s Anti- Oxidant Concentrate plus a pure bioflavinoid product such as Hesperidin Bioplex (Uckele). Hesperidin Bioplex is a concentrated source of bioflavinoids and contains 5.5 grams of vitamin C per ounce.
We have also had good preliminary results supplementing with grape seed extract. Grape seed extract is a potent anti-oxidant that has been used as a poultice to shrink skin melanomas. The horses treated with grape seed extract Equine Bioquench (Uckele) showed complete disappearance of exercise-related cough, improved exercise tolerance, greatly improved recovery times from exercise and improved lung sounds within three weeks of beginning the program. (Vitamin C and Hesperidin were also used but had been supplemented in excess of 45 days before starting the grape seed extract.)
Treatment Of Moderate To Severe COPD: When the horse is at the stage where he has been officially diagnosed as having heaves or COPD, prescription medications must come into play.
Corticosteroids and either epinephrine or atropine will usually be given by injection to achieve rapid control. The steroids stop the runaway inflammation, while the epinephrine will immediately help dilate the airways and improve ease of breathing. When large amounts of mucus are present, sodium iodide treatment intravenously helps thin the mucus so it moves out of the lung.
In a veterinary hospital, the horse may be treated with a nebulizer containing medications such as Mucomyst, a drug that also liquefies mucus. Many veterinarians will also use injectable antibiotics in the early stages of treatment for an acute attack of COPD, not necessarily because infection is involved but rather because the irritated lung is more susceptible to infections, and corticosteroid treatment.
Even though corticosteroids always carry some risk of side effects, their use in the treatment of COPD attacks is almost mandatory. The root of this disease is a runaway immune system, and only corticosteroids can effectively control this. Benefits far outweigh risks in these horses.
The only other class of drugs with potential effect against those immune responses responsible for COPD is the antihistamines. However, most veterinarians agree that antihistamines have little, if any, effect and are no substitute for corticosteroids.
Bronchodilators of the theophylline family (e.g. Theophylline, aminophylline, Albuterol, clenbuterol) are also widely used. Horses with signficant breathing problems between attacks are often maintained on these drugs to help prevent flare -ups and make the horse more comfortable. Severe cases may also require steroid therapy. An effective treatment schedule, and one that almost eliminates the risks associated with chronic steroid use, is to treat the horse with a relatively low dose of steroid on an every-other-day treatment schedule.
Cromolyn sodium is helpful in some human asthma. It helps stabilize histamine-containing cells. Studies in horses have shown some benefit, but this drug is expensive and is only effective in helping prevent attacks, not in treatment. Your veterinarian may suggest cromolyn sodium before exercise, however.
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