Phylogenetic and pathogenic analyses of two virulent Newcastle disease viruses isolated from Crested Ibis (Nipponia nippon) in China

The crested ibis is one of the most endangered birds in the world, found only in Shaanxi Province in Central China, and it has been reintroduced in Sadogashima in Japan. Two Newcastle disease virus (NDV) isolates were collected from sick crested ibises, and their pathogenic and phylogenetic characteristics were investigated. The results showed that they are virulent, with intracerebral pathogenicity indices of 1.46-1.83 and a mean time of death of 54.4-84.4 h. They shared the same virulent motif ¹¹²-R-R-Q-K-R-F-¹¹⁷ at the F protein cleavage site. The phylogenetic analysis revealed that both isolates were clustered with class II NDVs, with one in genotype VIId and another in a novel genotype (provisionally designated as VIi). The two isolates shared high homology with the strains isolated from poultry flocks in the same region from 2006 to 2010. We first isolated and characterised the NDV isolates from crested ibises, one of which showed new genetic characteristics and formed a new subgenotype with isolates from pigeons and ostriches in the same area. These data are useful for further epidemiological studies on NDV and the protection of crested ibises.