Estimation Of Infectious Dose 50 (ID50) And Immune Response to Salmonella Gallinarum in Vanaraja Layers

Abstract

Salmonella Gallinarum causes fowl typhoid, a systemic disease with significant economic and welfare implications in poultry. This study aimed to determine the Infectious Dose 50 (ID₅₀) of S. Gallinarum in Vanaraja layer chickens and evaluate histopathological changes and immune responses. Chickens were intraperitoneally inoculated with escalating doses of S. Gallinarum (2×10⁹, 4×10⁹, 8×10⁹, and 1.6×10¹⁰ CFU), and the ID₅₀ was estimated to be approximately 8.0×10⁹ CFU. Higher doses induced clinical symptoms, including mortality and liver damage characterized by congestion and necrosis. Serum antibody responses, specifically IgG and IgA, were significantly elevated in a dose-dependent manner. Additionally, flow cytometry (FACS) analysis revealed a marked activation of CD3⁺, CD4⁺, and CD8⁺ T-cells, indicating robust cellular immunity. These findings underscore the pathogenicity of S. Gallinarum and highlight the need for enhanced biosecurity measures, improved management practices, and the development of vaccines to mitigate its impact on poultry health.