Airway Reactivity in Rural vs. Urban Horses

As cities continue to grow, so does pollution. It is only natural to think that horses might be affected by this pollution, since studies have found that exposure to air pollution particulate matter contributes to respiratory problems in humans. During the General Medicine Session, a joint study between researchers at the Environmental Protection Agency and Tufts University School of Veterinary Medicine was presented on “Airway Reactivity, Inflammation, Iron, and Iron-Associated Proteins in Urban vs. Rural Horses.” Multiple studies have shown that certain metals found in air pollution, including iron, might be responsible for airway injury and inflammation in humans. Due to the seriousness of small airway inflammatory disease (SAID) in horses, this study tried to identify whether airway reactivity was greater in urban vs. rural horses due to iron particulate matter in the environment.

Airway reactivity in thirteen urban horses (living less than 40 miles from a city or manufacturing center) and 11 rural horses (living more than 40 miles from a city or manufacturing center) was evaluated by measuring inflammatory cells in bronchoalveolar lavage fluid (BALF). In addition, levels of iron, ferritin, and lactoferrin (proteins that work to decrease oxidative stress) in BALF were measured.

Urban horses had a higher iron level in BALF when compared to rural horses, as was expected; however, this result was not statistically significant (p=0.08). Interestingly, rural horses had a significantly higher incidence of airway reactivity than did the urban horses. This was opposite from what the researchers expected to find--it seems likely that environmental triggers other than air particulate matter might contribute to airway reactivity.

In addition, urban horses had a trend toward greater levels of ferritin in BALF. The researchers hypothesized that the higher ferritin levels in horses from the urban areas reflect a protective mechanism against oxidative stress by storing the iron, causing less airway inflammation.

About the Author

Sarah Evers Conrad

Sarah Evers Conrad has a bachelor’s of arts in journalism and equine science from Western Kentucky University. As a lifelong horse lover and equestrian, Conrad started her career at The Horse: Your Guide to Equine Health Care magazine. She has also worked for the United States Equestrian Federation as the managing editor of Equestrian magazine and director of e-communications and served as content manager/travel writer for a Caribbean travel agency. When she isn’t freelancing, Conrad spends her free time enjoying her family, reading, practicing photography, traveling, crocheting, and being around animals in her Lexington, Kentucky, home.

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