Characterization of Newcastle disease viruses isolated from chickens and ducks in Tamilnadu, India.

摘要

During outbreaks of Newcastle disease on many farms in Tamil nadu, India, in 1993, 6 Newcastle disease virus (NDV) strains were isolated from the chickens on 5 farms and from the birds on one duck farm. All the isolates were characterized as velogenic, based on the mean death time, i.v. pathogenicity index, intracerebral pathogenicity index (ICPI), stability of haemagglutinin at 56oC, agglutination of equine erythrocytes, haemagglutination elution pattern and adsorption of haemagglutinin by chick brain cells. The isolate from ducks resembled a group D strain, based on its ICPI and its reaction with a panel of monoclonal antibodies. The other 5 NDV isolates from chickens were placed in groups B(1), CI(2) and D(2) on the basis of binding patterns with the panel of monoclonal antibodies. In challenge experiments, the LaSota vaccine provided 100% protection against each of these field isolates and against a local NDV strain obtained from the Institute of Veterinary Preventive Medicine, Tamil nadu, India. The origin of outbreak viruses vaccinated flocks is discussed.