Endoscopic findings, microbiological and cytological evaluation of tracheal aspirates in a population of Standardbred horses with poor performances

Sixty-two Standardbred horses housed at the same racetrack, with history of reduced exercise tolerance, cough lasting for at least two weeks and/or prolonged recovery time were clinically examined. An endoscopic examination of the nasopharynx, larynx and trachea to the level of the carina was performed, amount of mucus in trachea was registered and samples of tracheal wash for cytological and microbiological examinations was collected. A strong statistical association between amount of mucus in trachea and neutrophils percentage in tracheal wash was found. Bacteria isolated included Streptococcus equi subsp. zooepidemicus (14 horses), Streptococcus pneumoniae (four horses), S. mutans (four horses), S. equinus (four horses) and Burkholderia cepacia (10 horses). S. zooepidemicus and S. pneumoniae were associated with elevated amount of mucus and increased neutrophilic percentage. B. cepacia was associated with cytological evidence of haemosiderophages but its role in racehorses needs further investigations. Mycoplasma spp. and Pasteurella spp. have not been isolated, suggesting that, as for the other putative causes of inflammatory airway diseases, infection could have a regional distribution among horse populations. This study shows that various types of airway inflammations exist in the examined population and that S. zooepidemicus and S. pneumoniae could play an important role in etiopathogenesis of airway inflammation in some horses. Particulate matter, pro-inflammatory agents or noxious gases present in the stables or on the track matter, could be the cause of inflammation in non infected horses.