Skip to content
Search Library
thumbnail

Many airway diseases in horses may be described as asthma, from mild inflammatory airway disease to severe, life-threatening heaves. While we may still picture a weary, aged horse struggling to breathe as the epitome of asthma, this crippling condition knows no boundaries, negatively affecting the performances of young, apparently healthy horses as well.

One recent study* reported that inflammatory airway disease correlating to mild asthma occurs relatively commonly in Thoroughbred racehorses that appear clinically normal. The veterinarians, including Laurent Couëtil, one of the lead authors on the most recent equine asthma consensus statement**, collected 98 lung wash samples (bronchoalveolar fluid or BALF) from 64 horses between 24 and 48 hours prior to a race.

“Analysis of the lung fluid diagnosed mild asthma in 52 of the 64 horses,” explained Catherine Whitehouse, M.S., a Kentucky Equine Research nutrition advisor. This meant 80% of the tested horses were affected.

BALF analysis also found that mast cells rather than neutrophils (both types of inflammatory white blood cells) dominated the airways of horses with mild asthma. This finding was not necessarily unexpected as previous studies found older horses with inflammatory airway disease mostly harbored neutrophils whereas young horses had mast cells and eosinophils, suggesting different disease processes.

What was especially eyebrow-raising, however, was finding that only 16 of the 64 horses performed well based on a first-, second-, or third-place finish during the study period.

“All horses included in the study were actively racing and perceived as healthy, yet their performances clearly left much to be desired,” said Whitehouse.

Further number-crunching by the researchers revealed that an increase in BALF mast cells or neutrophils correlated with decreased performance. Specifically, for each percent increase in BALF mast cell count, the slower the horses raced. A similar finding for neutrophil counts was also observed, but the decrease in speed was not as remarkable.

“In sum, this research revealed that mild equine asthma occurs commonly in young racing horses, has a negative influence on racing performance, and is predominantly caused by mast cell inflammation,” Whitehouse said.

In terms of treatment, Couëtil and colleagues summarized their evidence-based recommendations in 2016 in what remains the most up-to-date guidelines for managing the disease. In brief, currently recommended treatment strategies include:

  • Antigen avoidance;
  • Use of anti-inflammatory corticosteroids (e.g., oral, inhaled, nebulized);
  • Administration of bronchodilators to increase the diameter of the small airways; and
  • Feeding omega-3 fatty acids (fish oil) that possess natural anti-inflammatory properties.

Kentucky Equine Research’s fish oil supplement EO-3 is a rich source of DHA and EPA, two important omega-3s.

“EO-3 is top-dressed onto the feed and helps many horses with asthma, including young, athletic horses with inflammatory airway disease,” noted Whitehouse.

For improved management, review these eight important tips to minimize the development of disease and reduce the severity of asthma attacks when they occur.

*Ivester, K.M., L.L. Couëtil, G.E. Moore. 2018. An observational study of environmental exposures, airway cytology, and performance in racing Thoroughbreds. Journal of Veterinary Internal Medicine. 32(5):1754-1762. 

**Couëtil, L.L., J.M. Cardwell, V. Gerber, et al. 2016. Inflammatory airway disease of horses—Revised  consensus statement. Journal of Veterinary Internal Medicine. 30(2):503-515.

X

Subscribe to Equinews and get the latest equine nutrition and health news delivered to your inbox. Sign up for free now!