COMPARATIVE STUDY ON THE PATHOGENICITY AND IMMUNOGENICITY OF NEVVCASTLE DISEASE VIRUS STRAINS M AND K

A local isolate of Newcastle disease virus (NDV—M) was evaluated for its pathogenicity and immunogenicity and compared with that of Komarov (K) strain to assess its utility as a vaccine strain. Pathogenicity studies by mean death time, intracerebral pathogenicity index, and intravenous pathogenicity index have shown that NDV-M is also a mesogenic strain but distinct from strain K. Newcastle disease virus strain M was pathogenic to day old chicks causing 26.6% mortality while chicks aged three and six weeks were resistant. An increase in HI antibody titres was noticed in chicks inoculated with strain M, the peak titers being recorded during the 3rd and the 4th week. On challenge at the 8th week 100% protection was observed. Statistical analysis of the antibody titers by MWU test have shown that strain M had a significantly higher immunogenic effect than strain K. Contact infection with NDV-M was less effective (25-26.8%) than that of NDV-K (62.5-75.0%).