Rhodococcus equi infection in Marwari male foal: A case report

A 2-months-old Marwari male foal was anorectic, febrile, and showed difficulty in breathing. Haematology revealed anemia and severe neutrophilic leukocytosis with left shift. Symptomatic treatment was given, however the animal died within 48 hours. On necropsy, multifocal, raised, well-demarcated, off-white to grey, firm, abscesses of 10 to 15 cm diameter effaced the normal lung parenchyma. Colon wall showed multifocal to coalescing, raised, well-demarcated, off-white to grey, firm, transmural, variable-sized abscesses. On histopathological examination, the lung showed pyogranulomatous bronchopneumonia. Frequently cytoplasm of macrophages was filled with numerous fine basophilic bacteria. Colon showed necro-pyogranulomatous inflammation with intracytoplasmic bacilli. On Taylor’s Gram staining of tissue, the cytoplasm of macrophages was filled with numerous blue Gram-positive bacilli. Sample collected at the time of necropsy were subjected to microbiological and molecular investigation. Based on colony morphology, bacterial morphology, gram reactivity, and biochemical tests, the isolates were presumptively diagnosed as Rhodococcus equi (R.equi). Further, the isolates were confirmed as R. equi by species-specific primers. Moreover, all the isolates were also found positive for the presence of virulence-associated antigens (VapA), indicative of the pathogenic nature of the isolates. This case report described R. equi induced bronchopneumonia, and colitis in foal