A 3-month-old Friesian colt was referred for evaluation of severe ataxia and inability to rise unassisted since birth. The colt appeared bright and alert, and its temperature (38.2°C [100.8°F]), heart rate (68 beats/min), and respiration rate (32 breaths/min) were within expected ranges for an excited foal. Examination of its cranial nerves did not reveal any abnormalities, but proprioceptive deficits were evident in all 4 limbs, especially the pelvic limbs. The colt would repeatedly knuckle in all 4 limbs and had episodes of pelvic limb spasticity. The colt was restricted in its ability to flex its neck laterally and ventrally,
Objective—To describe the clinical and laboratory findings, diagnostic features, and outcome of tracheal collapse in American Miniature Horses at a referral institution.
Design—Retrospective case series.
Animals—13 American Miniature Horses with tracheal collapse.
Procedures—Medical records of American Miniature Horses with tracheal collapse at a referral hospital were reviewed. Data extracted included signalment, history, clinical signs, laboratory data, diagnostic procedures, outcome, and histologic findings.
Results—Tracheal collapse was documented in 5.6% of American Miniature Horses admitted to this referral hospital. Median age at onset of clinical signs was 11 years with a range of 2 to 15 years. Common complaints and clinical signs included respiratory distress, tachypnea, inspiratory honking noises, and increased abdominal expiratory effort, which were exacerbated by stressful events, pregnancy, exercise, a dusty environment, and eating. Tracheal collapse was confirmed by use of radiography, endoscopy, fluoroscopy, or postmortem examination. Dorsoventral flattening of the extra- or intrathoracic trachea, or both, was more common than lateral collapse. Tracheal chondromalacia was identified histologically in 4 cases, and mortality rate for affected horses was 10 of 13.
Conclusions and Clinical Relevance—Tracheal collapse was relatively common in this study of American Miniature Horses, and outcome was poor. The etiopathogenesis of the disease remains unknown.