French research holds promise of simpler IAD test

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French research may lead to the development of a simpler test for inflammatory airway disease (IAD) in horses.

IAD is a common cause of poor performance in the equine athlete.

Affected horses may cough as well as show exercise intolerance, but a definitive diagnosis is based on examination of bronchoalveolar fluid.  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 A small amount of fluid is introduced and withdrawn, and the cells that have been washed from the lung are collected and examined microscopically.

The French research holds the promise of a simpler test, the latest issue of Equine Science Update reports.

Eric Richard and his 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 the disease.

A surfactant protein 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.

The protein 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 levels of the protein before and after exercise in horses with and without inflammatory airway disease, has been reported in the Equine Veterinary Journal.

Forty-two standardbred racehorses were used in the study.

Blood samples were collected from each horse before, and 60 minutes after, they had completed a standardised treadmill exercise test. Tracheal wash and bronchoalveolar fluid samples were also collected after exercise.

On the basis of the fluid’s characteristics, the horses were classed as either being affected with IAD (22 of the 42 were) or not (20 of the 42 animals).

The researchers found that IAD was associated with a detectable, though moderate, increase in levels of the protein in the blood.

Within the IAD-affected group, they found no significant correlation between serum concentrations of the protein and bronchoalveolar fluid cytology. Nor did they find a significant effect of exercise on the protein’s 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 authors of the report advise that more work is needed to understand the factors controlling blood levels of the protein. They advise caution before applying their findings to clinical cases.

Funding for the study was provided by the 2010 French Equine Veterinary Association Research Award.

 

Serum concentration of surfactant protein D in horses with lower airway inflammation.
EA Richard, PH Pitel, U Christmann, P Lekeux, G Fortier, S Pronost.
Equine Vet J (2012) 44; 277-81.
doi: 10.1111/j.2042-3306.2011.00421.x.

Equine Science Update

 

 

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