Longitudinal Tracheal aspiration (TA) and Bronchoalveolar Lavage (BAL)

Several factors are known to give variations in TA and BAL cytology; the most important factor is lower airway diseases such as inflammatory airway disease (IAD) and recurrent airway obstruction (RAO). Factors such as age of the horse, the stabling environment and dust exposure, season of the year and the genetic background of the particular horse are also described to affect the TA and BAL cytology results. Furthermore, variations in the endoscopic examination, the TA and BAL sampling and subsequent laboratory procedure also affect the cytology results.

Longitudinal studies on how the stabling environment and management strategies affects the lower airway of horses is lacking.

The objective of this study was to evaluate the inflammatory changes in the airway (evaluated by mucus score, TA and BAL) of conventional stabled horses over a life-long period.

An observational cohort study design was used. Including a homogenous group of healthy riding horses (n=50- 75 yearly) over a 12-year period, starting 2005, with sampling once a year (between May and early July). Horses were included in the population at the year of 5-6 and would stay until retirement as a riding horse. During the 12-year period, 27 of the horses were sampled during at least 10 consecutive years. Each year a clinical examination, endoscopy including mucus score, TA and BAL was performed . The results of the TA and BAL has let to improvement of management and daily routines over the years. Between year 2005 and 2006 the bedding material was changed from straw to wood pellets and between year 2008 and 2009 the hours at pasture has been increased. From the start to year 2008 the volume used for BAL was 120 ml, from year 2010 to 2012 a volume of 180ml was used and from year 2014 a volume of 250ml was used. The laboratory procedures were the same for all years. Total cell count was manually performed and cytospin smears was made and stained with May-Gründwald Giemsa. A microscopic evaluation of five hundred leukocytes including neutrophils, lymphocytes, alveolar macrophages, mast cells and eosinophils. Results from this study will be presented at WEAS 2017.