Analysis of the presence of Beta-hemolytic streptococci and cytological profiles in horse tracheal lavage samples with diverse clinical respiratory symptoms

Horses with coughing and lymph node swelling showed the highest prevalence of β-hemolytic streptococci. S. zooepidemicus infection was associated with increased neutrophils and decreased macrophages and lymphocytes, highlighting the role of neutrophils in inflammation. Asymptomatic horses may also carry the bacteria, indicating their role as carriers. Distinct inflammatory profiles correspond to clinical signs, underscoring the complexity of equine respiratory disease and the value of cytology and tracheal wash in diagnosis.