Co-circulation of genetically distinct groups of avian paramyxovirus type 1 in pigeon Newcastle disease in Iran.

Pigeons are considered as one of the major natural reservoirs in the epidemiology of Newcastle disease (ND). In this study, the partial sequence of fusion protein gene of 17 pigeon-origin ND viruses (NDVs) isolated during 2012-2013 in Iran was analysed. Since the studied isolates showed F0 protein cleavage sites compatible with velogenic NDVs, all were considered as virulent NDVs. Two isolates carried 112RRQKRF117 as the cleavage site motif, whereas the rest demonstrated 112KRQKRF117 motif which just recently has been reported among Iranian virulent NDVs. Phylogenetic analysis divided all these diverse isolates in two distinct clusters within class II genotype VI. Based on the partial fusion protein gene sequence, 15 out of 17 isolates showed the highest genetic identity to subgenotype VIb/2 and the other two isolates were placed in a distinct genetic group of genotype VI. Based on recent findings, at least two different sublineages of genotype VI are causing the ND outbreaks in the pigeon population and are circulating simultaneously along with virulent NDVs of genotype VII in various species in Iran. The continuing circulation of a diverse group of virulent NDVs as an enzootic in widespread species such as pigeon can cause outbreaks in commercial poultry flocks and also failure in controlling programmes. Therefore, the constant monitoring and awareness of the virus characteristics should be considered in controlling programmes against ND in Iran.