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OVC Researchers Study Impact of Smog on Horse Lung Health

Harness racing horses in Nova Scotia_iStock credit_CapeBretonerResearchers at the University of Guelph are looking at the effect of outdoor air pollution, or smog, on the respiratory health of horses in the Guelph-Kitchener-Waterloo area.

In humans, increased air pollution is known to play a role in the development and triggering of asthma. The components of air pollution that contribute to the development of asthma in people include fine particulate, nitrogen dioxide, and ozone. Dr. Janet Beeler-Marfisi, a professor in the Department of Pathobiology at the Ontario Veterinary College, is looking to see if the same factors play a role in the development of mild equine asthma (MEA) in horses.

Mild equine asthma is common in young sport horses, and its effects are particularly important in racehorses. Symptoms of the disease include intermittent cough and increased numbers of inflammatory cells in the lower airways. As racehorses are elite athletes, any decrease in lung health, such as cough or inflammation, has a large and negative impact on athletic performance. Beeler-Marfisi’s interest in smog and MEA stems from her own struggles with asthma and her love of Standardbred racehorses.

Dr. Janet Beeler-Marfisi, Ontario Veterinary College, University of Guelph “The role of air pollution hasn’t been fully investigated in horses,” says Beeler-Marfisi. “We wanted to determine if a relationship exists between increased air pollution or temperature and asthma in horses.” To help people with asthma, the Ontario government has a website with the Air Quality Health Index (AQHI). This is a tool used by asthmatic Ontarians to determine how much outdoor activity is safe for them when air pollution and the AQHI are high. “We really wanted to see if the AQHI could be used by horse trainers to predict when they should avoid high intensity training in order to protect their horse’s lung health, because it would be easy for them to access this information on the web.”

Her research team retrieved records from cases at the Animal Health Laboratory at the Ontario Veterinary College, in which cell samples had been taken from the horses’ lower airways. They pared down the data to make sure that the samples were taken from horses in specific geographic regions with similar air quality and that had reliable weather and air quality recording programs.

From there, Beeler-Marfisi and her team looked at the meteorological data corresponding to the time that these horses developed lung issues to see whether temperature also affected these horses.

Her research group identified 154 Standardbred racehorses with records that fit their criteria. Of these, 78 cases had increased levels of lung inflammatory cells. On average, the horses were four years old, which is young. This means that that 51 per cent of the racehorses in the Guelph-Kitchener-Waterloo area had MEA during this 10-year period – which is high and means that these horses could have had reduced athletic performance as a direct result of exposure to air pollution.

Although it is unclear exactly how temperature affects asthma in humans, increased ambient temperature was another risk factor for the development of MEA in horses.

These findings support the idea that inflammation of the respiratory tract in horses, develops in a similar way to asthma in humans in response to air pollution.

Whether the AQHI itself could be used by horse trainers and owners to protect their horse’s lung health, was not clarified by this study. However, because two of the components of the AQHI were associated with lung inflammation in horses, it suggests that another study with a greater number of horses would be able to determine the AQHI’s usefulness.

“This is the most comprehensive study investigating the relationship between outdoor air pollution and lung inflammation in horses. And it’s the first to examine the association of the AQHI with horse lung health” says Beeler-Marfisi. “Our results expanded on the current understanding of how exposure to higher air pollution can affect the health of horses in the Guelph-Kitchener-Waterloo area, and has identified air pollution as an important target for future research in MEA and other lung diseases of horses”.

This research was funded by a grant from Equine Guelph.

Learn more about Dr. Beeler-Marfisi's research in an Equine Guelph article and video.