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Heaves, also known as recurrent airway obstruction (RAO), is a chronic respiratory disease of horses. It is similar to that of asthma in humans. Heaves is a common and serious condition that affects 15% of mature horses (typically over seven years of age).
Heaves develops more commonly in horses that are stabled and are exposed to dust, mites and mold from bedding or hay, irritants such as ammonia (from urine and feces) and bacterial irritants. Once the small particles are inhaled, they enter the lower respiratory tract, causing inflammation and mucus accumulation. As this occurs, the small airways deep in the lung, called bronchioles, constrict. Over time repeated bouts of inflammation can cause permanent changes to the lung, and the walls of the airway become irreversibly thickened. As the disease progresses it is more and more difficult for the horse to breath.
• Cough at start of exercise (early development of disease)
• Frequency of coughing increases
• Increased effort to breath at rest
• Nasal discharge but no fever
• An obvious abdominal lift at the end of exhalation
• A heave line
• Weight loss due to difficulty of eating while trying to breathe
Diagnosing heaves in a horse is a difficult task and not as straightforward as one would think. A physical examination by a veterinarian familiar with horses is very important. A veterinarian may also recommend an endoscopy (scoping) to better visualize the airways. Typically a bronchoalveolar lavage (BAL or lung wash) is performed to help diagnose the condition. The samples allow for your veterinarian to evaluate for the presence of white blood cells. If there are a significant number of white blood cells, it further supports heaves as a possible diagnosis.
The most important treatment for a horse diagnosed with heaves is environmental management. It is recommended to keep your horse on pasture more than in a confined stall area. Be sure to provide shelter so that the horse can be protected from the elements and has adequate forage available. Try to treat and clean the bale and stall areas to remove any possibility of ammonia as well as additional dust particles. It is also recommended to offer a complete pelleted feed or hay cubes; try also to wet these down if possible. If you do offer hay, try spreading it on the ground to encourage mucus drainage from the airways as the horse puts his/her head down to graze.
Try to avoid mucking stalls, sweeping shed rows and running tractors while the horses are stabled. It is not ideal to offer hay, even if soaked in water, as there are still dust particles circulating in the air. If at all possible try to avoid feeding horses from round bales. Horses tend to stick their noses in the center of the bales as they eat, which then causes them to have even greater exposure to dust, mites, molds and other particles.
If environmental management is not enough at managing heaves, oral or inhaled steroids are typically used as well as bronchodilators. The steroids help by decreasing inflammation of the airways and the bronchodilators help to relax and dilate the airway muscles, so air can flow in and out of the lungs.
Currently there is no cure for heaves. Once a horse’s airway is sensitive to the particles, it is a lifelong disease requiring lifelong medication and environmental management. Acupuncture has been shown to be helpful in managing this condition alone or in addition to conventional therapy. If you suspect your horse has heaves, please contact your veterinarian for an examination.
[Joseph A. D’Abbraccio, DVM, of Catskill Veterinary Services, PLLC, can be contacted at firstname.lastname@example.org. For more information visit https://www.facebook.com/CatskillVeterinaryServices or www.catskillvetser vices.com.]