Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON NIG 2W1, Canada; e-mail: email@example.com.
Pulmonary Eosinophilia Associated with Increased Airway Responsiveness in Young Racing Horses
Article first published online: 28 JUN 2008
© 1998 American College of Veterinary Internal Medicine
Journal of Veterinary Internal Medicine
Volume 12, Issue 3, pages 163–170, May 1998
How to Cite
Hare, J. E. and Viel, L. (1998), Pulmonary Eosinophilia Associated with Increased Airway Responsiveness in Young Racing Horses. Journal of Veterinary Internal Medicine, 12: 163–170. doi: 10.1111/j.1939-1676.1998.tb02112.x
- Issue published online: 28 JUN 2008
- Article first published online: 28 JUN 2008
- Accepted September 30, 1997
Horses are known to acquire small airway disease (SAD), an allergen-induced naturally occurring syndrome of reversible obstructive lung disease accompanied by airway hyperresponsiveness and increased inflammatory cell numbers on bronchoalveolar lavage (BAL). This disorder has received scant attention in young racehorses. The purpose of the present report was to examine the effect of BAL eosinophilia in young racehorses on clinical examination, BAL, hematology, airway responsiveness, and on pulmonary function at rest and after a standardized exercise challenge. Five (3 males, 2 females; age 2.6 ± 0.9 years) with a history of respiratory compromise and BAL eosinophil differential count <5% and 6 controls (4 males, 2 females; age 3.5 ± 1.0 years) training and performing to expectation with normal BAL cell differential (eosinophils < 1%) were studied. Respiratory system clinical examination was performed and expressed as a clinical score. Arterial blood gas measurements, CBC, and pulmonary function testing were performed at rest. Pulmonary mechanics measurements were repeated 1 hour and 20 hours after a standardized treadmill exercise challenge. Incremental histamine inhalation challenge was performed and the concentration of histamine effecting a 35% decrease in dynamic compliance (PC35CDyn) was determined. Significant differences were noted between and controls with regard to clinical score (P= .01), blood eosinophils (P= .04), BAL cell count (P= .04), BAL macrophage differential (P= .04), PC35CDyn (P= .008), and tidal volume and respiratory rate at 20 hours following exercise challenge (P= .05). We conclude that pulmonary eosinophilia and airway hyperresponsiveness are manifest in some young horses without overt airway obstruction at rest. We speculate that these may be early events in the natural progression of heaves.