DIAGNOSING INFLAMMATORY AIRWAY DISEASE AND EXERCISE
INDUCED PULMONARY HEMORRHAGE IN POORLY PERFORMING
RACEHORSES (105 CASES, 1996-2001)
Alfredo Sánchez*, Laurent L. Couëtil, Michael P. Ward§,
Veterinary Clinical Sciences, §Veterinary Pathobiology, Purdue University School
of Veterinary Medicine, West Lafayette, IN 47907-1249 USA
Inflammatory Airway Disease (IAD) is a common and widespread
respiratory tract disease in racehorses manifested as exercise intolerance, cough
and evidence of mucus in the airways on endoscopic evaluation.
Exercise
induced pulmonary hemorrhage (EIPH) has also been implicated in decreased
performance in racehorses, and is manifested as presence of blood in the
tracheobronchial tree after a race.
An initial diagnosis of IAD and EIPH can be made based on the history,
physical examination and clinical signs. To confirm the diagnosis, other tests may
be performed, including cytological evaluation of bronchoalveolar lavage (BAL)
fluid and arterial blood gas analysis during high-speed treadmill exercise.
The purpose of this study was to compare BAL cytology and arterial blood
gas analysis during a standardized treadmill test (STT) in control and IAD and
EIPH racehorses presented to Purdue University Equine Sports Medicine Center
(ESMC) for poor performance.
One hundred and five horses with history of respiratory disease presented
to the ESMC for treadmill evaluation between January 1,1996 and December
31,2001. A sole diagnosis of IAD and EIPH was made in 18 and 14 horses,
respectively. IAD and EIPH were diagnosed when endoscopy of the trachea
post-treadmill exercise revealed evidence of mucupurulent discharge and blood,
respectively. 10 horses with no history or diagnosis of EIPH or IAD were used as
controls.
Horses affected with IAD had a significantly higher BAL neutrophil count
(59.4 ± 48.3 cells/μl) and percentage (10.5 ± 7.4 %) than control horses (18 ±
29.5 cells/μl, 3.8 ± 5.5 %, P<0.05). The degree of exercise-induced hypoxemia
was significantly more pronounced in horses with IAD than in controls (P<0.05).
Horses with EIPH showed values intermediate between control and IAD horses.
In conclusion, racehorses with IAD exhibit airway neutrophilia and
impaired blood gas exchanges during exercise. EIPH has a variable effect on
pulmonary gas exchanges.