Heat Waves, Pollen Could Worsen Equine Asthma Signs

Heat Waves, Pollen Could Worsen Equine Asthma Signs

Recent study results suggest that heat waves and pollen—not just dusty hay and surroundings—could also be associated with increased asthma severity in horses.

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Horse owners in many locations are counting down the days to spring and summer—longer days, no snow and ice, and warmer weather to ride in! But could this change in temperatures wreak havoc on a horse with equine asthma? Recent study results suggest that heat waves and pollen—not just dusty hay and surroundings—could also be associated with increased asthma severity in horses.

“Asthmatic horses already experiencing mild to moderate clinical signs show a rapid worsening of clinical signs during heat waves when temperature and humidity increases suddenly,” explained Michela Bullone, DMV, a PhD student under the direction of Jean-Pierre Lavoie, DMV, Dipl. ACVIM, a professor and the director of the Equine Asthma Research Laboratory at the University of Montreal, in Canada.

Researchers have not yet studied the effect of acclimatization to heat and humidity. However, the team believes the threshold of temperature and humidity that triggers an equine asthma attack depends on the history of temperature and humidity the horse has previously been exposed to.

The study also revealed that an increase in airborne pollen concentration on hot days could play a role, Bullone said. There is no evidence that pollen alone prompts an attack, but it might act in concert with other triggers as nonspecific irritants for the airways of asthmatic horses, she said, adding that “further studies will need to clarify this.”

An environment with good air quality and ventilation is crucial for all horses with asthma, regardless of the severity. “Horses with asthma are better managed when kept at pasture and access to hay is avoided,” Lavoie said.

When full-time pasture turnout is not an option, owners can take steps to prevent or reduce asthma attacks, including:

  • Feeding silage, haylage, and/or pelleted hay rather than dry hay;
  • Stabling asthmatic horses as far from hay or straw storage as possible;
  • Minimizing environmental dust through frequent sweeping and wetting of barn and stall floors,
  • Installing insulation to prevent abrupt environmental changes; and
  • Using fans and/or air conditioning to prevent sudden temperature rises.

“Preventive medicine (such as regular vaccinations and good biosecurity protocols) is currently primarily implemented for the control of infectious diseases, but we believe it could bring significant advantages in the management of noninfectious pulmonary conditions, as well,” Lavoie concluded.

The study, “Environmental heat and airborne pollen concentration are associated with increased asthma severity in horses,” was published in the Equine Veterinary Journal

About the Author

Katie Navarra

Katie Navarra has worked as a freelance writer since 2001. A lifelong horse lover, she owns and enjoys competing a dun Quarter Horse mare.

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