High Genetic Diversity of Newcastle Disease Virus in Wild and Domestic Birds in Northeastern China from 2013 to 2015 Reveals Potential Epidemic Trends

Abstract

Newcastle disease (ND), caused by the virulent Newcastle disease virus (NDV), is one of the most important viral diseases of birds globally, but little is currently known regarding enzootic trends of NDV in northeastern China, especially for class I viruses. Thus, we performed a surveillance study for NDV in northeastern China from 2013 to 2015. A total 755 samples from wild and domestic birds in wetlands and live bird markets (LBMs) were collected, and 10 isolates of NDV were identified. Genetic and phylogenetic analyses showed that five isolates from LBMs belong to class I subgenotype 1b, two (one from wild birds and one from LBMs) belong to the vaccine-like class II genotype II, and three (all from wild birds) belong to class II subgenotype Ib. Interestingly, the five class I isolates had epidemiological connections with viruses from southern, eastern, and southeastern China. Our findings, together with recent prevalence trends of class I and virulent class II NDV in China, suggest possible virus transmission between wild and domestic birds and the potential for an NDV epidemic in the future.

FIG 1

ND outbreak events in China between 2005 and 2015. The asterisk indicates data cutoff on June 2015. All data were collected from the OIE official website (http://www.oie.int/wahis_2/public/wahid.php/Diseaseinformation/statusdetail).

FIG 2

Sample collection sites in Jilin Province. Sampled cities or areas are indicated by color. The number of samples and positive rates of NDV are annotated.

FIG 3

Phylogenetic analysis of complete F gene sequences (1,662 nucleotides). Class I and II sequences are indicated as gray and white circles, respectively. Only bootstrap values of ≥50% are shown. The evolutionary history was inferred by using the maximum-likelihood method based on the general-time-reversible model. The tree with the highest log likelihood (−11262.9423) is shown. The percentage of trees in which the associated taxa clustered together is shown next to the branches. Initial tree(s) for the heuristic search were obtained by applying the neighbor-joining method to a matrix of pairwise distances estimated using the maximum-composite-likelihood approach. A discrete gamma distribution was used to model evolutionary rate differences among sites (four categories [+G, parameter = 0.6973]). The rate variation model allowed for some sites to be evolutionarily invariable ([+I], 0.0000% sites). The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The analysis involved 58 nucleotide sequences. All positions containing gaps and missing data were eliminated. There were a total of 1,662 positions in the final data set. Evolutionary analyses were conducted using MEGA 6.06.

FIG 4

Isolation sites and years (A) and percentages (B) of class I NDV clusters in China. Sampled provinces in this study are indicated by a star in panel A. The asterisk in panel B indicates the data cutoff on 20 November 2015. All data were obtained from GenBank (http://www.ncbi.nlm.nih.gov/GenBank/).