Abstract
This case report describes the following scenario: A 56-day-old Arabian filly presented with classical symptoms of respiratory distress and a rapidly deteriorating condition, despite intensive antimicrobial treatment, resulting in death. The post-mortem examination revealed severe bronchopneumonia with characteristic disseminated pus-containing nodules. Microbiological tests and PCR confirmed the presence of R. equi carrying the virulence-associated protein A (VapA) gene. The isolate was sensitive to macrolides and fluoroquinolones but showed resistance or intermediate susceptibility to several commonly used antimicrobials. This case highlights the diagnostic and therapeutic challenges posed by this intracellular pathogen and emphasizes the importance of early detection, targeted therapy, and biosecurity measures-especially in the absence of an effective commercial vaccine.