A horse diagnosed with "heaves" has been known by many names over the years. At one point the disorder was commonly referred to as COPD, short for chronic obstructive pulmonary disease, a condition that is linked to tobacco smoke in humans. Because COPD in humans is very different than heaves, the term COPD is no longer used in reference to horses. Instead, the American College of Veterinary Internal Medicine recommends the disorder be termed recurrent airway obstruction (RAO) or heaves. Heaves is more similar to human asthma and involves inflammation and constriction of the lower airways of the lung.
Dr. Kara Lascola is a clinical assistant professor at the University of Illinois Veterinary Teaching Hospital in Urbana, who specializes in equine internal medicine. She explains that, "horses with RAO tend to be older, with owners often complaining of exercise intolerance and episodes of dyspnea [difficulty breathing]. Cough and nasal discharge may or may not be present."
Some horses may even have more severe signs such as flared nostrils, wheezes on expiration, and a heave line. A heave line is a classic symptom in horses with long-standing heaves. Because they are using increased effort to exhale air out of their lungs, the abdominal muscles used in breathing become more developed. This muscle development creates a visible line (heave line) around the bottom of their rib cage.
Diagnosing these horses can sometimes be complicated especially if the condition is not very severe. "Horses may initially present with subtle clinical signs," explains Dr. Lascola, so it is important to rule out other causes of airway inflammation such as an infection, or a completely different type of respiratory disease called inflammatory airway disease (IAD).
In some cases, a good history will lead to a diagnosis of heaves, but in others, a bronchoalveolar lavage may be necessary. This procedure involves collection and evaluation of fluid present in the airways of the lungs. It is relatively quick and may be performed while the horse is standing and sedated. The fluid is viewed under a microscope to look for certain types of inflammatory cells and the presence of mucous or possibly pollen spores--all of which can provide important information about the cause and severity of the disease.
Dr. Lascola is also using a new, noninvasive lung function test to improve the diagnosis of airway disease in horses. Similar lung function tests have been used for the diagnosis of asthma in humans. Of course the challenge veterinarians face, compared to human physicians, is encouraging a 1,200-pound horse to exhale on command. The device used by Dr. Lascola, as well as many other veterinarians, has been designed to overcome these challenges in order to better diagnose equine patients with certain respiratory diseases, such as heaves or inflammatory airway disease.
As for treatment, the most important component is environmental management. A strong link exists between exposure to allergens such as mold and dust and the development of heaves. It is important that the horse be housed to minimize exposure to potential allergens. Full or increased turn-out on pasture and reduced exposure to hay dust are critical. In addition, your equine veterinarian may prescribe corticosteroids and bronchodilators to reduce the inflammation and constriction of the airways.
For more information on heaves, please contact your local equine veterinarian.
An archive of Pet Columns from the University of Illinois College of Veterinary Medicine is available online at www.vetmed.illinois.edu/petcolumns/. Requests for reprints of this article may be directed to Mandy Barth, email@example.com.
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