A longitudinal study of velogenic Newcastle disease virus genotypes isolated in Italy between 1960 and 2000

Thirty-six representative velogenic strains of Newcastle disease virus isol ated in Italy since 1960 were characterized by restriction site and partial sequence analyses of the fusion protein gene. Viruses belonging to the six known genotypes of Lomniczi et al. were found. Genotype IV, which was most probably the main epizootic group in Europe before the war, was responsibl e for outbreaks in the 1960s and persisted until the late 1980s in Italy. A n epizootic peak in 1972 to 1974 coincided with the appearance of genotype V viruses that were present for more than a decade. Outbreaks in 1992 were caused by genotype VIIa viruses and were part of a contemporaneous epizooti c of Far East origin that affected Western European countries. The Newcastl e disease epizootic that commenced in Italy in May 2000 was due to a genoty pe VIIb virus that is indistinguishable from those causing sporadic outbrea ks in Great Britain and Northern Europe in the late 1990s. Isolated cases y ielded a variant of genotype VI (reference epizootic: Middle East in the la te 1960s) and a group VIII virus (enzootic in South Africa).