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OVC Expert Contributes to Global Paper on Equine Asthma

Dr. Dorothee Bienzle, Ontario Veterinary College, University of Guelph An equine researcher at the University of Guelph’s Ontario Veterinary College (OVC) is furthering global knowledge about equine asthma.

Dr. Dorothee Bienzle, in OVC’s Department of Pathobiology, has an established research program focused on better ways to diagnose and treat inflammatory lung diseases such as asthma in horses.

She contributed to a recently published large collaborative research paper – The current understanding and future directions of Equine Asthma research, a follow-up to an international workshop on equine asthma in 2019.

Funded by the Havemeyer Foundation, the workshop brought together more than 50 participants including microbiologists, clinicians, pathologists and other researchers all exchanging ideas, and sharing information. “It was a wonderful opportunity to get together with people from all over the world who study equine asthma and respiratory disease,” says Bienzle. “We are very grateful to the Havemeyer Foundation and the organizer, Dr. Laurent Couetil, for making it all possible.”

The workshop provided a chance to share ideas on topics such as: what early onset versus late stage asthma looks like and how it manifests in horses affected by pasture environments versus stable-associated asthma. There was discussion of fungal spore inhalation off the pasture grasses in asthma found in hot, humid climates in comparison to the asthma found in Northern climates where researchers are confident asthma is caused by inhalation of a combination of fungal spores, bacterial components and most likely dust.

Scoping image of bronchus from asthmatic horse and non-asthmatic horseBienzle and her team concentrate on the host response to challenges like dusty barn air by looking at the epithelium in the lung. The respiratory epithelium moistens and protects the airways, produces mucus and other substances, as well as acting as a physical barrier to pathogens.

By the time a horse presents with severe equine asthma, also known as heaves, t the disease is close to the end stage. By taking biopsies of the epithelium in horses with heaves, researchers look at the genes and proteins that are present and expressed. Changes in the epithelium typically include inflammation, airway remodeling and fibrosis, to name a few.

“The goal would be to identify the disease early during onset, which might allow the disease to be reversed,” says Bienzle.

Through next generation sequencing, Bienzle and her team have distinguished differences in gene expression between asthmatic and non-asthmatic horses. They have looked at signature variants that may indicate a susceptibility to asthma. They have identified a lack of certain anti-inflammatory proteins such as club cell secretory protein (CCSP) that may assist in developing better defense systems when it comes to treatment and prevention. A lack of repair functions has been observed in horses with end stage equine asthma such as a reduced ability to produce cytokines in adequate amounts (cytokines are small proteins that signal within the immune system) and the inability to recruit undifferentiated epithelial cells to repair epithelial damage.

Unfortunately, at this time there are no early predictors of equine asthma. “It may be possible that bouts of inflammatory airway disease at a younger age could predispose horses to asthma in later years but as of yet such evidence is not available,” adds Bienzle, explaining the need to follow a large group of horses over their lifespan to come up with better predictors.

Bienzle offers these take-away messages for horse owners dealing with heaves: early diagnostics, aggressive treatment and, most importantly, environmental management. Intervention is recommended at the first sign of a cough, especially if the cough is repetitive or persistent. Bronchoalveolar lavage (BAL) is the gold standard diagnostic test for asthma. Corticosteroids administered with a bronchodilator may be prescribed to help the horse recover from bouts of equine asthma but environmental improvement is the key. The best advice is to get them out of dusty barns and into fresh air.

Adds Bienzle: Until the advent of early diagnostics, the focus for equine asthma needs to be first on prevention, and second on management and environmental improvement.
 

Watch the video interview with Dr. Bienzle
YouTube Video Link:
https://youtu.be/zZtkGCvRhd8

This story first was published in Equine Guelph’s Annual Research Update – Volume 18 January 2021. Read the entire publication.