Presenter Francesca Tomlinson
Authors Francesca Tomlinson (1), David Sargan (1), Jane Ladlow (1, 2)
Affiliations 1. Department of Veterinary Medicine, University of Cambridge 2. Granta Veterinary Specialists, Cambridge
Presentation Type Poster
Abstract
Introduction: Pathological tracheal cartilage phenotypes are common in certain toy and brachycephalic canine breeds. These tracheal abnormalities can contribute to airway narrowing in brachycephalic obstructive airway syndrome (BOAS), leading to difficulty breathing and exercise intolerance. Tracheal hypoplasia is commonly noted in the English Bulldog narrowing their airways, whilst in the Pug, tracheomalacia contributes to dynamic airway collapse. This study aimed to investigate tracheal morphology and its association with BOAS in fourteen other brachycephalic breeds.
Methods: In this study, a large sample population of brachycephalic dogs underwent respiratory function grading (n = 898) to assess BOAS severity on a scale of 0 to 3. Clinical signs of tracheal collapse such as ‘goose-honking’ or a positive tracheal pinch test were noted. A computed tomography (CT) study was performed in a smaller sample of brachycephalic dogs (n = 190) and morphometric measurements were taken of the trachea at the level of mid-body of cervical vertebra C4. Tracheal collapse ratio (TrC-R) was calculated from the height and width, and tracheal cross-sectional area was normalised to body surface area (TrCSA-BSA). Descriptive statistics were calculated for each breed. One-way ANOVA was used to compared BOAS Grades to TrCSA-BSA.
Results: A reduced TrCSA-BSA was found to be significantly associated with increasing BOAS grade severity (p < 0.0001). Clinical signs of tracheal collapse were particularly common in the Affenpinscher (26%, n = 69) and were only noted in eight dogs of other breeds (Boston Terrier, Chihuahua, Japanese Chin, Pomeranian and Staffordshire Bull Terrier). In the CT study, Affenpinschers were found to have marked tracheal collapse with a mean height to width ratio of 0.45 (SD = 0.21, n = 3). Boston Terriers were noted to have a comparatively smaller trachea for their weight (mean TrCSA-BSA = 162, SD = 31, n = 14), compared to the other breeds (whole sample mean TrCSA-BSA = 260, SD = 90).
Discussion/Conclusion: Tracheal collapse and tracheal hypoplasia are distinct pathological phenotypes in toy and brachycephalic dog breeds. Tracheal hypoplasia was found to be associated with BOAS status. Certain breeds such as the Boston Terrier were found to have comparatively smaller tracheas in relation their body size. Whilst tracheal collapse is common in small and toy breed dogs, compared to similar populations, the Affenpinscher is particularly prone to this condition. Underlying genetic mutations causing chondromalacia that result in tracheal collapse have yet to be identified in the dog. The Affenpinscher could represent a valuable model for identifying genetic variants associated with tracheal collapse.