Tracheal collapse in American Miniature Horses: 13 cases (1985-2007).

This research paper details a study on tracheal collapse in American Miniature Horses. The study, conducted at a referral institution, involved 13 horses and aimed to describe the findings, diagnostic features, and the outcome of the disease in this particular breed.

Objective and Methodology

• The objective of the study was to define the clinical and laboratory findings, diagnostic features, and the outcome of tracheal collapse in American Miniature Horses at a referral institution. The disease was investigated in a retrospective series of 13 cases, which were thoroughly reviewed and analyzed.
• Data extracted included signalment (a term that refers to the identification and description of the patient such as age, breed, and sex), history, clinical signs, laboratory data, diagnostic procedures, outcome, and histological findings. To confirm tracheal collapse, different diagnostic methods were used, from radiography, endoscopy, fluoroscopy to postmortem examination.

Results

• Data showed that 5.6% of American Miniature Horses admitted to the referral hospital had tracheal collapse. The median age at onset of clinical signs was 11 years, but the range stretched from 2 to 15 years.
• Common complaints and clinical signs included respiratory distress, tachypnea (rapid breathing), inspiratory honking noises, and increased effort to exhale that involved the horse’s abdominal muscles. These signs could be made worse by stress, pregnancy, strenuous exercise, dusty environments, and eating.
• The study identified two types of tracheal collapse: extra- or intrathoracic. The former was more common than the latter. Tracheal chondromalacia, which is the softening of the cartilages in the trachea, was histologically confirmed in 4 of the cases.
• The mortality rate for affected horses was high, with 10 out of the 13 studied horses dying.

Conclusion

• Tracheal collapse appeared to be relatively common in this particular study of American Miniature Horses, and the outcome for affected horses was generally poor. However, the cause and progression (etiology and pathogenesis) of the disease still remain unknown.