Horses with uncontrolled respiratory disease have more organs at risk than simply their lungs, new Canadian research shows. Drs. Serena Ceriotti, Michela Bullone, Mathilde Leclere, Francesco Ferrucci and Jean-Pierre Lavoie have discovered that horses with uncontrolled respiratory disease are at risk of having pulmonary arterial changes that could lead to heart failure.
Horses that suffer from severe equine asthma have inflamed airways; they also cough and have difficulty breathing. The researchers hypothesized that this condition, which is triggered by dust and mold in a horse's hay and environment, can put horses at risk of pulmonary hypertension. Pulmonary hypertension occurs when the walls of the pulmonary arteries thicken and increase the horse's blood pressure.
For the study, the research team obtained multiple post-mortem lung samples from 18 horses: six that were in heaves episodes when they died; six that were in remission from heaves from being kept in a dust-free environment; and six that had no heaves and served as controls.
The researchers measured the thickness of the arteries and found that horses with uncontrolled asthma had thicker arterial walls than other horses in the study.
Why the artery walls thicken when a horse has breathing trouble is unknown, but it is hypothesized that the low oxygen content and inflammation may increase the amount of smooth muscle in the artery walls, which makes it more difficult for blood to move out of the lungs. Eventually, this condition could lead to an enlargement and failure of the right ventricle of the heart.
The final part of the team's study focused on potential treatments for pulmonary hypertension in horses: they used 11 asthmatic horses divided into two groups that were treated for a full year with two different treatment protocols. One group had reduced dust exposure, primarily through the feeding of hay alternatives. The second group went on a corticosteroid for the first six months, the had dust control measures added in. Both treatments led to a reversal in arterial wall thickness, but changes in the second group were not seen until the dust control measures were taken.
They scientists determined that the thickening of arterial walls in horses with heaves can be reversed, but environmental changes must be made; the administration of corticosteroids, while helpful, must be made in conjunction with changes in management.
Read the full study here.
Read more at EQUUS magazine.
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