A REVIEW OF CYTOLOGICAL SPECIMENS FROM HORSES WITH AND WITHOUT CLINICAL SIGNS OF RESPIRATORY-DISEASE

Thirty-six transtracheal washing (TTW) and 12 bronchoalveolar lavage (BAL) specimens collected in clinical practice from horses with and without respiratory disease were reviewed. Cytological features were considered in accordance with the presenting complaint, clinical signs, clinical diagnoses, microbiological, radiographic and/or endoscopic findings, therapy, and response to therapy. The trichrome-stained TTW and BAL specimens were useful in interpreting the results of concurrent microbiological cultures, and determining whether a condition was present based on occurrence of typical cytological features of patterns (e.g. probable allergy, chronic obstruction, uncomplicated exercise-induced pulmonary haemorrhage), determining pathological/anatomical diagnoses (e.g. bronchitis, bronchiolitis and/or alveolitis; presence of metaplasia or dysplasia) and possible aetiologies (e.g. allergy, bacterial infection). Review of these cases confirmed the practicality of using cytological specimens to evaluate the equine respiratory tract; there were few unsatisfactory specimens and no reported complications. The importance of cytological evaluation of the equine respiratory system was emphasised by the identification of 13 cases in which clinical signs were not apparent at physical examination. Sequential collections of cytological specimens from foals, young horses before and during early training, and mature horses in training may provide more information about the response of the equine lung to stresses associated with training and/or common environmental exposures.