NEW (GENETIC) GROUPING OF NEWCASTLE-DISEA SE VIRUS (NDV) STRAINS

Restriction site analysis of the fusion (F) genes of more than 200 New castle disease virus (NDV) strains was performed. A majority of the F gene was amplified by reverse-transcription (RT) - polymerase chain re action (PCR) and PCR products were analysed by three restriction enzym es (Fig. 1). Restriction site maps of NDV strains were constructed (Fi g. 2) and strains were classified into six major genetic groups (Table 2). Members within groups were not only closely related genetically b ut they had common origin geographically or epidemiologically. Strains of North American origin were found in group II, while pandemic strai ns isolated in the last fifty years were classified into groups III-VI . Strains isolated from current outbreaks in Europe belong to group VI . Pigeon paramyxovirus-1 strains constitute a separate branch in group VI and are closely related to viruses that were isolated in the Middl e East at the late 1960s. Vaccine strains have individual restriction site pattern and they can be distinguished from each other.