Summer Dust Can Trigger Respiratory Woes The episodic respiratory illness commonly known as heaves or “broken wind” was until
recently termed chronic obstructive pulmonary disease (COPD) in the medical literature. It has been renamed recurrent airway obstruction (RAO) to indicate that it is not the same condition as COPD in humans. RAO in horses takes two main forms: barn-associated heaves and summer pasture-
associated heaves. In both cases, the disease involves a number of factors, including exposure to respirable dust particles (especially aeroallergens such as mold spores and pollens), ineff ective lung clearance and possibly even genetic predisposition. Both types of RAO also share similar symptoms, which include: ◗ chronic coughing, especially in recurrent episodes ◗ production of mucus when coughing ◗ labored breathing and elevated respiratory rate ◗ increased abdominal movement during breathing ◗ fl ared nostrils while resting ◗ nasal discharge ◗ exercise intolerance ◗ depression
Where the two forms diff er is in their trigger factors and management. Barn-associated
RAO is triggered by confi nement to a stable environment, inadequate stable ventilation and organic dust particles found in hay and bedding. These horses typically do very well when turned out on pasture, and the recommendation is generally to keep them outdoors as much as possible. With summer pasture-associated RAO, however, horses are sensitive to grass pollens and mold spores found in grasses, and should therefore be kept indoors during the grass-growing season. Because horses with summer pasture-associated RAO are likely to have ineff ective
lung clearance overall, it is important to ensure a low-dust environment for them in- doors, as well. Hay should be thoroughly soaked (wetting is not enough) or replaced with a pelleted source of fi ber, and bedding should be a low-dust product such as peat moss, high-quality shavings, rice hulls or shredded newspaper. The barn and individual stall should also be well ventilated, and soiled bedding must be removed frequently to reduce the build-up of ammonia fumes, which can be irritating to horses with RAO. Other helpful measures include removing the horse when the stall is being cleaned, and storing hay in a separate building. Additional treatment measures may include the use of corticosteroids to reduce
infl ammation, and bronchodilators may be given to relieve spasms in the airways. RAO is diagnosed through history (especially of recurrent coughing episodes), physical exami- nation and blood work, and may also include radiography, endoscopy, bronchoalveolar lavage (BAL) and pulmonary function testing.
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