| Featured Article - April 2008
In The Shadow of Equus Heaves |
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| When
our mare Zona, a 20-something Anglo-Arab with some mustang blood in her
veins, arrived on the coast from the prairies in the early 1980s, she
had been suffering bouts of heaves for some time. To help ease her
laboured breathing, we invested in good quality clean hay, kept the
barn well aired and clean, and allowed her and all the horses outside
all day except in extreme weather. We soaked her hay, taking a cue from
her habit of dunking mouthfuls of hay in her water bucket before
chewing them. The changes in her management worked to some degree,
especially in cooler weather, but she was always susceptible to
something in the air that could trigger an attack. As our little Thoroughbred, Lucy, aged, she was beset with a lung condition best described as emphysema. Her hay is soaked, she enjoys all-day turnout in the fresh air, and she has daily medications of antihistamines, a steroid product and a third medication to keep her bronchial passages open. Today 31-year-old Lucy continues to breathe with relative comfort even though her lungs are hugely compromised. For every equine athlete, lung health is ground zero for the high performance expected of them. Of all lung conditions though, heaves is perhaps the most well known yet the least understood. It is often not recognized until a horse develops an airway hyper-reactivity syndrome similar to asthma in humans. Allergenic substances produce compounds that trigger bronchial spasms leading to inflammation and damage to the air sacs in the lungs where oxygen transfer takes place. Once that happens, it is damage control rather than treatment for a cure. Heaves takes a heavy toll on many horses and it is a huge cost to the equine industry. To understand both the syndrome and its impact, Assistant Professor Renaud Leguillette with the Faculty of Veterinary Medicine, University of Calgary, has embarked on a series of research projects on heaves starting with an epidemiologic study based on a comprehensive online questionnaire. Other studies include molecular biology of the cells in the lungs, mechanics of the lungs, and clinical trials for new treatments. |
“Horses are athletes,”
explained Prof. Leguillette. “(They)
don’t use much of their lung function capacity when at rest or doing
light exercise. If the horse is not training hard when lung function is
important, the disease can spread into the lung without being noticed
for a while. Once the clinical signs are noticed by owners, most of the
small airways are usually affected by inflammation.” Through the epidemiologic study, Leguillette hopes to determine the frequency of heaves in Alberta horses, identify the risk factors, determine the cost of the disease to the equine industry, and find out if there is a correlation between asthma in horse owners and heaves in their horses. “We know that heaves is a chronic inflammatory lung disease triggered by exposure to environmental organic particles,” said Leguillette. “Horses suffer episodes of respiratory distress due to constriction of their lungs’ airways. There is no cure for heaves and treatments (either) have side effects or are not always effective. Prevention is key to avoiding heaves. However, risk factors are poorly identified making it very difficult to give good recommendations.” Given the evidence for climate change and shifting weather patterns, Leguillette is paying close attention to any connection between horses with heaves and weather conditions. A critical factor in managing horses with heaves is overseeing what they eat and maintaining quality control. In fact, says Leguillette, the link between heaves and the quality of hay was published in the 18th century in a French medical dictionary. While today the link between hay and heaves is well accepted, the actual evidence for the link is still lacking and Leguillette is researching that connection, especially now that horses are being fed not only baled hay but round bales with a higher moisture content. If you live in Alberta and would like to take part in the online questionnaire, you can do so at www.ucalgary.ca/heaves. You don’t have to have a horse with heaves to take part. To find out more about the study which is expected to continue well into the summer with some results possibly becoming available in the fall, contact Prof. Leguillette at rleguill@ucalgary.ca. |
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