E04 - Clinical and Microbial Alterations in Performance Horses Undergoing Long-distance Transport

Abstract:

Background: Transport-associated pneumonia leads to significant health, welfare and economic impacts in high-performance horses, and may be associated with alterations in the respiratory microbiota.

Hypothesis /

Objectives:
To examine the effect of long-distance transport on respiratory microbiota and correlate changes in microbiota diversity and composition with systemic and airway inflammation.

Animals: 17 client-owned performance horses transported from New England to Florida under optimized trailering conditions and 12 non-traveling horses (controls).

Methods: Physical examination, bloodwork, nasopharyngeal wash, endoscopy, tracheal aspirates, and thoracic ultrasound were performed 48 hours before, and 24 and 72 hours after transport (T1-3). Stationary horses were assessed 4 days apart. Upper and lower respiratory microbiota were characterized using high throughput 16S rRNA sequencing and correlated with clinical variables using constrained ordination. Transport effects were evaluated using repeated measures ANOVA, with post-hoc analysis based on data distribution (P < 0.05).

Results: Cortisol levels decreased post-transport (P=0.019), while ultrasound scores (P=0.012) and serum amyloid A (P=0.034) increased from T1-T3. Timepoint explained a small but significant portion of microbiota variability (P < 0.001). Upper airway differed from lower airway microbiota, which showed greater β-diversity (lower stability) (P < 0.001). Timepoint and ultrasound scores correlated with microbiota alterations, particularly lower respiratory (P=0.004). Abundance changes of plant-associated genera (Rhizobiales, Rhodopseudomonas Methylobacterium) drove tracheal microbiota variability.

Conclusions and Clinical importance: Even under standardized, optimized transport conditions, respiratory microbiota alterations occurred in healthy, athletic horses, correlating with ultrasonographic evidence of pulmonary inflammation. These results prompt examining the mycobiome (fungal population) to further understanding of transport-associated respiratory disease.