Little is currently known on the effects of jugular thrombophlebitis on future athletic performance of horses. The aim of the study was to evaluate the impact of jugular thrombophlebitis on performance.
Records from 91 horses with thrombophlebitis were studied. Signalment, history, clinical signs, diagnosis, and treatment were reviewed retrospectively from medical files. Performance was evaluated in two ways: a questionnaire was sent to the owners to obtain their subjective assessment of their horse's performance compared to the pre-thrombophlebitis level. In Standardbreds, the records of pre and post thrombophlebitis races were reviewed, when available.
Thrombophlebitis was diagnosed in 37 horses upon admission (Group 1) while 54 horses developed thrombophlebitis when hospitalized for an unrelated condition (Group 2). 37 owners (33%) answered the questionnaire and racing records were available for 31 horses. Twelve horses had died, no performance information was available for an additional 25 horses, 6 horses had never performed, so only performances of 48 horses were assessed. Owners reported that all but one non-racing horse had performances equivalent or improved following discharge. According to the owners' evaluation or race time evaluations, 64% of horses presented with thrombophlebitis (Group 1) and 85% of the horses who developed thrombophlebitis during hospitalization (Group 2) returned to their previous performance level. 84% of Standardbred racehorses returned to racing. In these horses, there were no significant differences between racing time prior to, and following thrombophlebitis. No significant difference in performance was also noted regardless of the primary diseases, the presence of unilateral or bilateral thrombophlebitis, or the treatment administered.
Results of the present study suggest that athletic performance of pleasure and performance horses are not affected by thrombophlebitis even if bilateral. However, thrombophlebitis in Standardbred racehorses is associated with a decreased return to racing, but when they do, their performances are not impaired.