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Partial sequence and residue substitution analyses of the fusion protein gene were performed for 68 strains of avian paramyxovirus type 1 of pigeons (PPMV-1), an antigenic variant of Newcastle disease virus (NDV) of chickens, derived from 16 countries between 1978 and 2002. The majority of isolates clustered into a single genetic lineage, termed VIb/1, within genotype VI of NDV strains of chickens, whereas a small number of isolates that originated in Croatia after 1995, grouped in a highly diverged lineage, termed VIb/2, indicating a separate host-switching event from that of VIb/1 strains. Four distinct subgroups of lineage VIb/1, Iraqi (IQ), early European (EU/ea), North American (NA) and recent European (EU/re) have emerged and circulated in the past decades. Subgroup EU/ea and NA strains were responsible for the main streams of infection in the 1980s, while EU/re viruses for infections in the 1990s. The degree of genetic diversity of viruses in the early phase of the epizootic suggested a prolonged infection period of the pigeon-type viruses prior to the emergence of the disease in the early 1980s. Shared derived character analysis showed a close genetic relationship to Sudanese viruses from the mid-1970, suggesting that PPMV-1 viruses could be of African origin. |
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