Results of cytological and microbiological examination using tracheal aspiration in race horses with lower respiratory tract disease

Abstract

Respiratory tract disease is the second most common cause of poor performance in racehorses after musculoskeletal disease. Lower respiratory tract disorders (LRTD) are common in thoroughbred horses of all ages. The aim of this study was to investigate whether there was any association between the microbiological and cytological examinations. Fifty horses ranging in age from 2 to 6 years were examined. Horses with only upper respiratory tract abnormalities identified by endoscopy (at rest) were eliminated from the study and horses with LRTD were used in this study. Tracheal aspirate specimens were collected for cytological and microbiological examinations. Thirty six horses had positive and 14 horses had negative cultivation. The isolated bacteria included β-haemolytic Streptococcus equi subsp. zooepidemicus (38.8%), Escherichia coli (22.2%) and other bacteria that were isolated at rates ranging from 0.4 to 1.8%. Percentages of neutrophils, lymphocytes, eosinophils, macrophages and mast cells were evaluated in the cytological examination. The percentages of neutrophils were significantly higher in the samples with isolated bacteria (35.75 ± 2.60%) compared to the samples from which bacteria were not isolated (16.79 ± 2.36%) (P < 0.001). This study shows that S. equi subsp. zooepidemicus could play an important role in the etiopathogenesis of LRTD. It also demonstrates the importance of evaluating the microbiological findings of the tracheal aspirate specimens from horses suffering from respiratory infections, in addition to performing a detailed clinical examination and other complementary tests that focus on the respiratory system, such as endoscopy and cytology of the tracheal aspiration.

Agents isolated from horses with respiratory system infection signs

“…Respiratory diseases have been reported to be among the most common diseases in horse breeding in countries around the world (Sharma et al 2017;Kasap et al 2018;Vitale et al 2019). In particular, unsuitable shelter conditions, crowded environments and unfavorable climatic conditions increase the exposure of horses to different respiratory pathogens (Wood et al 2005).…”

“…Str. zooepidemicus is the most frequently isolated bacteria (Chapman et al 2000;Bianchi et al 2018;Kasap at al 2018;Preziuso et al 2019;Bianchi et al 2020). In a study conducted by Broux et al (2016), nasal swaps taken from 103 horses showing signs of respiratory system infection were found to be 30% S. equi subsp.…”

“…Bianchi et al (2018) examined 50 lungs with bronchopneumonia and identified S. zooepidemicus in 21 of them. S. zooepidemicus (27.4%) and E. coli (15.6%) were isolated primarily from racehorses with lower respiratory tract disorders (Kasap et al 2018). In our study, S. zooepidemicus was the agent with the highest rate with 27.27%, and then, coagulase negative Staphylococcus spp., Klebsiella spp.…”

“…zooepidemicus), Staphylococcus aureus (S. aureus), Streptococcus pneumoniae (S. pneumoniae), Pasteurella spp., Actinobacillus spp., Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae), Bordetella bronchiseptica (B. bronchiseptica) and Mycoplasma spp. (Chapman et al 2000;Christley et al 2001;Wood et al 2005;Couetil et al 2016;Kasap et al 2018;Pusterla et al 2020;Nehal et al 2021) isolated. S. equi subsp.…”