Retrospective survey of bronchoalveolar lavage fluid cytology in Western Australian horses presented for evaluation of the respiratory tract: effect of season on relative cell percentages.

The research article presents a study that evaluated the cytological changes in the bronchoalveolar lavage (BAL) fluid of horses to examine if there is a seasonal influence on the prevalence of mast cell response. The study suggests that an increased concentration of mast cells in horses’ lungs is common, particularly during the spring season.

Research Methodology

• The authors conducted a retrospective review of the medical records of 228 horses that were presented for clinical evaluation for respiratory illnesses or poor performance issues where a BAL had been performed. The selected sample predominantly comprised racing horses aged between 2-6 years, the most common complaint being poor athletic performance.
• The research team analysed the BAL fluid cytology along with variable clinical factors categorised previously.
• The focus of the analysis was to detect any strong associations within the gathered data, which was statistically computed using the Chi-square test technique.

Results Overview

• Approximately 69.7% of the horses presented with abnormal BAL cytology.
• Nasal discharge was found to be the only significant clinical evidence differentiating between horses with normal and abnormal cytology.
• The most common type of cytopathologic dysregulation was a mixed cell response (accounting for 26.7% of the cases), characterized mainly by high percentages of neutrophils and mast cells. Equal frequencies of neutrophilic and mast cell response were observed.
• Only 6.1% of instances reported an exclusive eosinophilic response.
• 58.4% of horses that showed non-infectious lower airway inflammation had increased relative percentages of mast cells.

Conclusion

• The study results indicated a significant association between cell profiles and the season of the year. Mastocytosis or increase in mast cells was found to be more common during the spring season, while neutrophilic and eosinophilic responses were more common during the summer.
• Based on their findings, researchers suggest that a relative increase in mast cells may be the most common cytological profile in horses affected by lower airway inflammation, and this response is closely linked to the change of seasons.