Vol. 18 •Issue 16 • Page 22
Asthma, Race Horses and Eskimos
Do you live in one of those seasonal climates where winter means snow storms, icy roads and cold temperatures? A place where fuzzy slippers and a warm blanket are your best friends?
Are you one of those people who enjoy going for a brisk run even on a cold winter’s day? Or maybe you are someone who has to work outdoors performing strenuous activity even when temperatures are well below the freezing point.
If this describes you, you may have something in common with the famous Mr. Ed. Yes, Mr. Ed, the talking horse.
If you have ever experienced a dry, irritating feeling in the back of your throat while outside in those cold winter months, you may be exhibiting signs of mild airway injury, something you may be sharing with race horses. And horses are moving into a primary role for studying human conditions.
“Basically we needed something that could exercise at the level of a well-trained human,” said lead author Michael S. Davis, DVM, PhD, assistant professor of Physiological Sciences at Oklahoma State University, Stillwater. Hence, the use of horses. “In addition, it’s easier to train a horse than a dog to run on a treadmill,” he added.
Avalanche of Events
Researchers suggest winter athletes, sled dogs, meatpackers and fisherman share experiences that may trigger the beginning of a cascade of events leading to more serious conditions later.
According to a study conducted at Oklahoma State University, both athletes and horses seem open to infection after strenuous activities like handicap races or marathons. Exercise physiologists have subjective evidence suggesting that overexertion might open a kind of “window of susceptibility” for illness.
Their research involved horses exercising while breathing air at 23 degrees Fahrenheit and may help explain why flu season occurs in the winter, how asthma develops in humans, and why active horses get the heaves.
The study, Cold Weather Exercise and Airway Cytokine Expression, was published Feb. 10, 2005, in the Journal of Applied Physiology. Researchers explain how cold weather exercise can lead to asthma-like airway disease through the local induction of cytokines.
“The paper is part of an overall goal to prove exercising in cold weather can cause lung injury,” said Davis. “We were interested in finding out whether cold weather caused abnormalities in the lungs.”
According to researchers, cold induced human “ski asthma,” clinical signs of heaves or notably persistent coughing due to airway constriction quickly diminishes when the subject is removed from the offending environment. Heaves are quite similar to human asthma, including the fact that the initial cause of the hypersensitivity has not been explained.
Sled Dogs and Skiers
Study data show that strenuous exercise followed by exposure to environmental antigens promotes overproduction of antibodies to those antigens. Researchers noted that this uncertain etiology is similar to that of “ski asthma.” In their study, researchers looked at sled dogs as an animal model for human asthma.
“The idea that something as simple as cold air causes lung damage needs to be taken more seriously,” said Davis.
Since preventing someone from skiing is almost impossible, researchers suggest the next step is to find a way to avoid airway injury.
“There should be more attention paid to this situation,” he said. “The attention needs to be given to how we block the exposure to chronic airway disease.”
Since study authors conclude that these issues warrant further investigation (for which horse models are ideally suited), some areas of further research include: looking at viral immunity in cold-air scenarios, determining whether heaves is more prevalent in colder climates and among athletic horses (or formerly athletic ones) than in sedentary ones and determining the range of air temperatures where airway damage occurs.
Marc Willis is a South Carolina television reporter.