Blood Test May Identify Horses with Airway Disease

Horses with inflammatory airway disease (IAD) have impaired respiratory function and a decreased ability to exchange oxygen and carbon dioxide in the tiny air sacs in the lungs. Due to this impairment, IAD is a leading cause of exercise intolerance and poor performance in horses.

The standard diagnostic test for IAD uses bronchoalveolar lavage. This procedure involves passing a tube into a sedated horse’s lung to introduce a small amount of fluid, collect the fluid, and examine the cells that have been washed from the lung.

A simpler test under development would use a blood sample for diagnosis of IAD. Researchers at the Frank Duncombe Laboratory in France obtained blood samples from 20 healthy horses and 22 horses that had been diagnosed with IAD. Samples were drawn before and after each horse completed a 60-minute treadmill exercise test. Results showed that levels of surfactant protein D, a substance related to immune function in the alveoli (air sacs), was significantly higher in horses with IAD, both before and after exercise, than in healthy horses. This finding indicates that the alveoli are inflamed and may have been damaged, impacting the free exchange of oxygen.

Correct diagnosis is essential before IAD can be treated with medications and management changes. Use of a noninvasive blood test to diagnose IAD would reduce stress on the horse and expense for the owner.