Comprehensive Pathomorphological Evaluation of Systemic Bacterial Infection Leading to Multi-Organ Dysfunction in a Panthera leo

This study aimed to investigate the clinicopathological and pathomorphological alterations associated with systemic bacterial septicaemia in a captive lion. The study was designed as a single-case observational investigation conducted at Rajgir Zoo Safari, Nalanda, Bihar, encompassing the period from initial clinical presentation to post-mortem examination in a 14-year-old male Panthera leo. The animal exhibited nonspecific clinical signs such as anorexia, depression, respiratory distress and progressive systemic deterioration, which are often indicative of underlying severe systemic infection. Methodologically, a comprehensive evaluation was carried out including detailed haematological analysis along with thorough gross and histopathological examinations to assess multi-organ involvement. Haematological findings revealed marked neutrophilic leucocytosis, relative lymphopenia, thrombocytopenia and mild inflammatory anaemia, suggesting an acute septic and endotoxaemic state. Gross pathological examination showed hepatomegaly with friable pale-yellow parenchyma, severe pulmonary congestion and edema with petechial haemorrhages and bilateral renal congestion with loss of corticomedullary demarcation. Histopathological observations substantiated these findings, revealing extensive hepatocellular necrosis with intralesional rod-shaped bacteria, diffuse alveolar damage characterized by emphysema, fibrin deposition and inflammatory cell infiltration, marked lymphoid depletion in the spleen and renal tubular degeneration and necrosis with bacterial colonies within tubular lumina. These lesions are consistent with septicaemic nephropathy and early multi-organ dysfunction. The results underscore the rapid and fulminant progression of bacterial septicaemia in lions, mediated by systemic inflammatory response syndrome, endotoxemia and microvascular injury. In conclusion, early haematological screening, rapid diagnostic intervention and vigilant clinical monitoring are essential to mitigate mortality in captive wild felids, and systematic documentation of such cases will improve disease understanding and management strategies in zoological institutions.