Diseases of clinical relevance in endurance horses

Abstract

Endurance horses have to perform at a level that often exceeds the performance level of pleasure riding horses. Ridden distances per day are between 25-162 km nationally and as from 2020, 100-160 km, internationally. Despite good training for the event, demands on the horse may exceed their performance limit and as a consequence, this may lead to acute or chronic conditions affecting the musculoskeletal system, the cardiovascular system or other systems. In order to prevent horses from being overexerted, regular vet checks have to be carried out and passed during an endurance ride. Inspite of these checks, some horses require veterinary care after not qualifying to continue the ride. Problems that occur during the ride or during the vet checks may lead to the horse not being able to qualify for the next loop or be not fit to continue at the final vet. check. Irregular gait/lameness account for 59-65% of cases ("fail to qualify - irregular gait", FTQ-GA). Inflammatory lesions of the suspensory ligament, the superficial flexor tendon, bruised front hoof soles, as well as generalized or local muscle conditions and iliosacral joint problems are relatively common. Chronic lameness is most likely to be caused by osteoarthritis of the fetlock and tarsal joints. Limb fractures can occur but are uncommon. All severe cardiovascular findings, such as not reaching the correct heart rate within 20 minutes in the vet check at national events or 15 min at international events; severely reduced gut sounds, clinical signs of severe dehydration or the subjective impression of fatigue, lead to the horse not qualifying due to metabolic reasons ("fail to qualify - metabolic", FTQ-ME) accounting for 15-17% of cases, second after musculoskeletal problems. One of the most common metabolic conditions during an endurance ride is colic (20-40% of horses fail to qualify during the race for this reason). Further common problems are exertional rhabdomyolysis, dehydration, diarrhoea, exhaustion, synchronous diaphragmatic flutter (SDF) and laminitis. Exercise-induced pulmonary hemorrhage (EIPH) occurs rarely in endurance horses. Metabolic problems may be severe and fatal without treatment. Further reasons for not qualifying to continue include bit or the saddle lesions, soft tissue injuries and wounds.