Animal Rabies Surveillance, China, 2004-2018

Abstract

Rabies is a severe zoonotic disease in China, but the circulation and distribution of rabies virus (RABV) within animal reservoirs is not well understood. We report the results of 15 years of surveillance of the first Chinese Rabies Surveillance Plan in animal populations, in which animal brain tissues collected during 2004-2018 were tested for RABV and phylogenetic and spatial-temporal evolutionary analyses performed using obtained RABV sequences. The results have provided the most comprehensive dataset to date on the infected animal species, geographic distribution, transmission sources, and genetic diversity of RABVs in China. In particular, the transboundary transmission of emerging RABV subclades between China and neighboring countries was confirmed. The study highlights the importance of continuous animal rabies surveillance in monitoring the transmission dynamics, and provides updated information for improving current control and prevention strategies at the source.

Keywords: China; genetic diversity; rabies virus; surveillance; transboundary transmission; viruses.

Figure 1

Phylogenetic analysis of 300 full rabies virus nucleoprotein sequences showed that RABVs in China could be classified into 4 major clades and 8 subclades. Bootstrap values = 1,000. Solid circles indicate sequences from this study; open circles indicate representative sequences from China previously published and retrieved from GenBank (Appendix Table 3). Unlabeled sequences are from surrounding countries; a few are vaccine sequences in the subclade of another Cosmopolitan clade. Named branches: dog isolates spilling out from wild animals; bold branches: wild animal isolates as indicated. SEA, Southeast Asia.

Figure 2

Geographic distribution of rabies virus clades and subclades in China and neighboring countries. The sequence information is from this study and GenBank (Appendix Table 3). SEA, Southeast Asia.

Figure 3

Spatial–temporal dynamics of RABVs in China. Phylogenetic analysis of 1,118 sequences representing 1,118 rabies cases or virus strains, including those obtained in this study using different gene fragments, followed by chronological summation of each subclade. A–C) Distribution of identified subclades during 3 time periods: A) before 2004; B) 2004–2008; C) 2009–2018. D) Quantitative trends of 8 Chinese RABV subclades during 2004–2018. Exact numbers within each subclade are given below the circles. SEA, Southeast Asia.

Figure 4

Nucleoprotein gene–based maximum clade credibility tree of rabies viruses. The estimated time to most recent common ancestor of these clades and their 95% highest posterior density values are indicated. The same sequences as in Figure 1 were used, except for those of 5 vaccine strains listed at end of Appendix Table 3. Black solid squares indicate strains from China. SEA, Southeast Asia.

Figure 5

Proposed transboundary transmission of rabies viruses between China and neighboring countries determined by the Bayesian stochastic search variable selection approach. Unbroken lines: transmission events with a Bayes factor >3; broken line: transmission event with a Bayes factor <3. SEA, Southeast Asia.