New study will examine macrophase responses to agents that cause this condition in horses

What happens if the quarterback of the immune system goes rogue?

In a study set to begin in June 2023, Ontario Veterinary College researcher, Dr. Janet Beeler-Marfisi, will be looking at macrophage responses to the agents that cause asthma in horses.

Equine Asthma or “heaves” can cause exercise intolerance, difficulty expelling air, inflammation of lung epithelium and narrowing of Bronchus, persistent cough and nasal secretions from mucous production. All of the above can turn a riding horse into a pasture ornament and or in worst case scenarios, bring about important quality of life decisions. Don’t wait for these signs or a tell-tale heave line to appear before taking steps in your barn management to reduce dust, mold and particulates in your horse’s environment.

Dr. Beeler said 100,000 of 700,000 of horses in Canada are predicted to suffer from asthma and she followed with sage preventative advice:

• Purchase the best quality hay you can afford

• Steaming or soaking hay reduces the dusts that cause asthma

• Wet down the aisles before sweeping the barn and avoid sweeping dust into horse stalls

• Keep barns well ventilated – especially when the tendency is to close everything up for warmth.

While studies on equine asthma have been ongoing for over 40 years, we still don’t know why some horses are more prone to develop heaves when exposed to the same environmental factors as horses that do not get heaves.

While studies on equine asthma have been ongoing for over 40 years, we still don’t know why some horses are more prone to develop heaves when exposed to the same environmental factors as horses that do not get heaves. Much focus has been placed on researching lymphocytes (white blood cells that help the body fight viruses) but Beeler’s study will be looking at macrophage responses, because they are the cells that “call the shots”.

“When the horse breathes in some dust, it’s a macrophage that tells the horse’s immune system whether it’s something they can safely ignore or something that they should respond to,” says Beeler. “To me, it makes sense to study the cells that call the shots, rather than those being told what to do (lymphocytes).”

The culprits of asthma come in the forms that are plentiful around the barn. From the endotoxins found in manure to the dust found in the hay they eat. Beeler says, “Even good quality hay will have some fungal spores or mold spores in it and that has a role to play in the development or heaves in horses that are susceptible to it.”

Beeler’s study aims to find out if macrophages, the quarter backs of the horse’s immune system, are behaving like they should when these challenges to the horse’s respiratory system are encountered. Communications from the macrophage’s nucleus (the computer or brain of the cell) are sent through messenger RNA which tells the rest of the cell (or factory) to make proteins (the product) – proinflammatory or anti-inflammatory proteins, for instance. This research seeks to reveal whether macrophages of heaves horses are the true culprit in the development of heaves.

Equineguelph offers these additional suggestions for defending againts dust in other areas of your faciluty:

In the arena:

• Choose footing wisely and replace or partially replace when needed. Fine smooth particles are more prone to suspension than heavier angular particles.

• Footing in the arena needs to be regularly maintained to remain moist, keeping dust from rising into the air.

• Additives and environmentally friendly oils help bind particles and slow evaporation.

In addition, horses should be kept outside as much as possible, unless medical conditions require stalling or the horse has an equine asthma issue associated with the pasture. If your horse begins to cough, call the vet right away to investigate the cause. When dealing with respiratory ailments early diagnostics, aggressive treatment and environmental management are of paramount importance.

Jackie Bellamy-Zions is an Equine Canada Certified Level 2 Eventing Coach and "r" Dressage Judge. She is a member of the Communications & Administration Team at the University of Guelph in Canada. It is a unique partnership dedicated to the health and well-being of horses, supported and overseen by equine industry groups. Equine Guelph is the epicentre for academia, industry and government – for the good of the equine industry as a whole. For further information, visit www.equineguelph.ca. You can email Jackie directly at: english_coach@yahoo.ca