Research Note: Disease tolerance/resistance and host immune response to experimental infection with Pasteurella multocida A:1 isolate in Indian native Nicobari chicken breed

ABSTRACT Indigenous chicken breeds are considered to be more disease tolerant than exotic chicken breeds especially for the bacterial diseases. Nicobari and Vanaraja chicken were evaluated for the survivability/mortality patterns and host immune response after experimental infection with P. multocida A1 isolate. The birds were inoculated with 1.9 × 105 CFU/ml through intraperitoneal (I/P) and intranasal (I/N) routes at two different age groups viz., 12 weeks and 18 weeks. Symptoms, mortality rates, lesions in dead birds were observed; Serum from surviving birds of different groups from both breeds were collected at 5, 14, 21, 28, 35 and 42nd day and specific antibody titres were measured by indirect ELISA. At 12 weeks of age, the mortality rates were 100% and 16% in birds inoculated by I/P and I/N routes respectively in Vanaraja birds; whereas the mortality rates were 50% and 16% I/P and I/N routes respectively in Nicobari birds. At 18 weeks of age the mortality rates were 16% and 50% for I/P routes in Nicobari and Vanaraja birds respectively. The mortality rates were 16% for I/N route in both Nicobari & Vanaraja birds. Lesions such as necrotic foci on liver, congestion in the liver were observed in dead birds. Serum titres were significantly (P