2017 ACVIM Forum Research Abstract Program

Valacyclovir is a relatively expensive drug that is routinely used to treat horses with EMPF. This study revealed that 10 days of valacyclovir treatment did not significantly alter viral kinetics of EHV-5 as measured by qPCR in nasal swabs, blood and bronchoalveolar lavage fluid samples. Exercise-induced pulmonary hemorrhage (EIPH) is diagnosed and severity assessed by post-exercise tracheobronchoscopic examination (TBE), and/or enumeration of erythrocytes (RBCs) in bronchoalveolar lavage fluid (BALF). TBE EIPH scores range from 0 to 4, 0 indicating no EIPH. BALF RBC < 1000/lL indicates no EIPH. There is scant information regarding the relationship of TBE EIPH score to BALF RBC number. We hypothesized that BALF RBC was weakly correlated (r 2 < 0.20) with TBE score. TBE followed by BAL was performed 223 times on 151 different horses after treadmill (8 horses, 45 runs), racetrack (6 horses, 24 runs), or barrel racing (143 horses, 155 runs) exercise. TBE EIPH score ranged from 0 (n = 83) to 4 (n = 5). RBC number ranged from 0 to 994,000/lL. Eleven TBE scores were 0 despite RBC count > 1000/lL. There were 61 exams with TBE scores ≥ 1 but BALF RBC counts < 1000/lL. The relationship between TBE score and BALF RBC number was significant but weak (P < 0.001; r 2 = 0.19) after Spearman's evaluation. TBE EIPH score was weakly correlated with BALF RBC number and there were large ranges of BALF RBCs associated with each TBE score. An EIPH score of 0 does not rule out the occurrence of EIPH, but neither does a BALF RBC count < 1000/lL. The latter finding was unexpected and may be explained by fast clearance of the respiratory tract or lavage of an airway segment other than the one bleeding. The possibility of technical errors counting RBCs in some samples cannot be discounted. Exercise-induced pulmonary hemorrhage (EIPH) refers to presence of blood in the airways caused by strenuous exercise. It has been documented in racing, polo and eventing horses, but little is known about EIPH in barrel racing horses. The purpose of this study was to test for the presence of EIPH in barrel racing horses, estimate its prevalence in the Pacific Northwest and determine whether a relationship between EIPH and performance exists.