Heaves is a disease that can leave a horse struggling to breathe. It can end athletic careers and even render a pleasure horse unsuitable for riding. Commonly known today as equine asthma, it’s irreversible and brought on by repeated exposure to dust and molds. Ontario Veterinary College researcher Doctor Bienzle has a long history of primary and collaborative work studying asthma in horses. Her most recent contributions include working with a group of researchers in Slovenia. These researches investigated stem cells as a potential treatment option.
Causes of Heaves
Bienzle explains that the usual causes of heaves are long-term exposure to dusty or moldy hay or bedding, dusty environments, and sometimes even grass in hot, humid climates that provide the right conditions for mold to thrive. “Horses get sensitized to these components in the inhaled air. With time, they develop airway inflammation and that begins to manifest with occasional coughing or runny nose.”
With continued exposure to the same particulates, the condition worsens, and the coughing becomes more continuous. The nose may be running and then there is thickening of the bronchial wall in the lung. There is extra smooth muscle being laid down. It becomes hard for the horse to exhale against mucus and inflammatory cells in the lumen of the airway.
In the later stages of disease, horses can develop a “heaves line” (hypertrophic abdominal muscles assist with exhaling air). By the time the horse receives a diagnosis, they have usually had equine asthma for a few years, if not several. Treatment of the symptoms includes immunosuppression. The disease is irreversible.
“The vast majority of the horses are unable to perform as athletic horses or even as companion horses with a little bit more strenuous riding,” says Bienzle. “It’s an incurable disease for most purposes. It’s somewhat treatable, but not curable.”
Dr. Bienzle elaborates on the importance of good hay, clean air and other important stable management considerations in a video interview. She goes on to explain the exciting new research investigating stem cells as a potential future treatment option.
Video Link: https://youtu.be/cgWk_VWuwdU
Management of Equine Asthma
The potential to downregulate inflammation with a biologic therapy like stem cells versus traditional drugs, like corticosteroids, is clearly attractive. For treatment administration, Bienzle explains there are already well-developed methods for examining the lower airway using endoscopes. Administering stem cells using this targeted method may be an appealing option versus intravenously where it is uncertain where the treatment ends up.
When explaining the challenges and expertise required to produce stem cells, Bienzle says, “This is not for the casual investigator. It takes some experience to have the right culture conditions to make sure those cells are clean. They are not cultured for very long. When administering the final preparation to an animal, it must be free of cell culture components that could make inflammation worse.”
The preliminary, proof-of-concept work is quite exciting, with stem cell therapy outperforming traditional corticosteroids. Stem cells have no side effects per se, which makes the study of biologic treatments very attractive.
This study, Effect of intrabronchial administration of autologous adipose-derived mesenchymal stem cells on severe equine asthma, published in Stem Cell Research and Therapy, was funded by the Slovenian Research Agency fund. The ground-breaking work is in its infancy, with researchers planning future studies. These could one day help horses and potentially humans suffering from asthma utilizing biologic therapy.
More tips on equine respiratory health are available for download at Equine Guelph.ca
Dr. Bienzle has recently been named to Canadian Academy of Health Sciences for outstanding contributions in the field of research.