Inflammatory airway disease (IAD) is a common cause of poor performance in the equine athlete. Affected horses may cough as well as showing exercise intolerance, but a definitive diagnosis is based on examination of bronchoalveolar fluid (BALF.) This involves passing a tube into a sedated horse’s lung. A small amount of fluid is introduced and withdrawn, and the cells that have been washed from the lung are collected and examined microscopically.
Research at a laboratory in France may lead to the development of a simpler test for IAD. Eric Richard and colleagues at the Frank Duncombe Laboratory at Caen have been investigating the value of a blood test for a protein present in the lung for identifying horses with IAD.
Surfactant protein D (SP-D) is produced mainly by specialised cells in the alveoli and bronchioles, but has also been found in joint fluid and in the reproductive tract. It plays a role in immune defences in the lung
SP-D is released into the blood stream in response to tissue damage, and is used routinely in human medicine as a marker for inflammatory lung diseases.
The study, which compared SP-D levels before and after exercise in horses with and without inflammatory airway disease, has been reported in the Equine Veterinary Journal.
The researchers found that IAD was associated with a detectable, though moderate, increase in SP-D levels in the blood.
Within the IAD-affected group, they found no significant correlation between serum SP-D concentrations and BALF cytology. Neither did they find a significant effect of exercise on serum SP-D concentration in either the IAD or control groups.
A non-invasive test for IAD would benefit both horse and owner, being less stressful for the horse and cheaper for the owner. However, the report's authors advise that more work is needed to understand the factors controlling blood levels of SP-D. They advise caution before applying their findings to clinical cases.
More details: equinescienceupdate.com