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06/01/2011 12:56.12 PM
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Summary
Heaves or broken wind is a respiratory disease of horses resulting in signs of chronic coughing, decreased exercise tolerance, difficulty breathing and abnormal lung sounds. These signs occur as the result of narrowing of the small airways of the lungs caused by: inflammation and thickening of their tissues; constriction of the smooth muscles that surround them; and accumulation of mucous and exudates within their lumens. The end result is trapping of air in the lungs (emphysema). Technically heaves is called chronic obstructive pulmonary disease (COPD). However, recurrent airway obstruction may be a better name because most cases go into remission when their environment is changed. Difficulty in breathing recurs when susceptible horses are again exposed to mouldy feeds or dusty conditions. Animals with clinical signs adopt a characteristic breathing strategy with very high peak flows at the start of exhalation which decreases rapidly as exhalation continues.
Causes of Heaves
Although heaves has been recognized as a disease of horses for centuries, its precise cause remains uncertain. Most published evidence suggests that the inflammation of the small airways (bronchiolitis) is the result of an allergic response that occurs following exposure of the lower airways to dust and moulds, particularly those that come from poorly cured hay.
Heaves occurs most frequently in the northern hemisphere (Europe and North America) among horses kept in stables. It also occurs in pastured horses in certain regions of Great Britain and the southern United States where it is thought to result from exposure to various pollens. Signs do not become obvious until a large number of airways are affected and therefore, many more horses are probably affected than is recognized. The disease is rare in warm dry climates and in New Zealand and Australia where horses spend little time in stables.
Common risk factors for the occurrence of clinical signs are exposure to poorly cured, mouldy or dusty feeds, confinement to a stable environment, inadequate stable ventilation, straw bedding and being 6 years of age or older. The incidence of the disease may be highest in ponies as they are frequently kept in less than ideal conditions and fed poor quality hay.
Other possible causes of heaves include specific toxins (3-methylindole) absorbed from the intestinal tract, exposure to cold air, genetic predisposition and viral respiratory infections. To date there is no solid evidence that any of these factors play a role in the occurrence of heaves but researchers are still exploring these theories.
Development of Heaves
Bronchiolitis (inflammation of small airways) is considered to be the most important abnormality of affected animals but spasm of the smooth muscles surrounding the bronchioles (bronchospasm) also plays a role. The airways of all horses become exposed to dusts, spores of moulds and a number of temperature resistant bacteria that are aeroCome visit me, Jet <3 <3 <3 RIP, Atlas VOTE OCTOBER HOTM!! PLEASE!! :), Bunny & Tigger R.I.P.
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06/19/2009 05:22.37 AM
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heres a vote, please come and vote for Timone he is running for HOTM! Come visit me, Sparkle & Timone.
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06/18/2009 03:24.08 PM
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