A SURVEY OF EXERCISE-INDUCED PULMONARY HEMORRHAGE IN QUEBEC STANDARD-BRED RACEHORSES

Sixty Standardbred horses, aged 3 to 10 years, were examined endoscopi cally for exercise-induced pulmonary haemorrhage (EIPH) 1 h after raci ng, on at least 3 occasions. Racing time, finishing position and post exercise venous lactate concentrations were also recorded. Horses posi tive for tracheal blood on endoscopy were classified as having either grade 1 EIPH (one or a few spots of blood in the trachea), or grade 2 (stream of blood). Air temperature, relative humidity and air pollutan t levels were recorded on each examination day. Of the 60 horses, 52 ( 87%) were EIPH-positive on at least one evaluation out of 3 and 40 of the 52 (77%) showed grade 2 EIPH on at least one occasion. Of the 52 E IPH-positive horses, 52% bled 3 times out of 3, 21% 2 out of 3 and 27% once. When only the first examination was considered, 37 of the 60 ho rses (62%) were EIPH-positive. There was no significant relation detec ted between either presence or frequency of EIPH and age, sex, or gait . Horses that showed grade 2 EIPH bled significantly (P = <0.001) more frequently (mean: 83% of examinations) than horses having shown no mo re than grade 1 EIPH (47% of examinations). No significant differences could be detected between EIPH-positive and EIPH-negative races in th e average racing times, finishing positions and blood lactate concentr ations of the 29 horses which showed intermittent EIPH. The proportion of horses showed EIPH on each day where at least 5 horses were examin ed was correlated with air temperature, relative humidity, and the lev els of several air pollutants on those days. There was a significant n egative correlation between air temperature and proportion of EIPH-pos itive horses (P = 0.0007, r2 = 0.39). No significant relations were de tected with relative humidity or air pollutant levels.