从流行毒株的系统发生看中国目前狂犬病流行的主要特征

以2006～2012年本实验室狂犬病病毒分离株核蛋白基因完整核苷酸序列和GenBank收录的主要数据为基础,通过构建系统发生树和比对病毒分离株相互间的同源性,对中国狂犬病流行特征进行分析.结果显示,目前涉及中国17个狂犬病主要流行省区的62个狂犬病病毒代表流行株,均为基因Ⅰ型,但在系统发生树上可分为i、ii、iii、iv、v共5个基因群,群内同源性91.4％～99.9％,群间同源性84.5％～90.1％.其中,i、ii群占国内新分离株的绝大多数,为2个主要流行基因群.i群遍布各主要流行省区,主要为来源于犬的分离株.ii群主要分布于南方省区,迄今分离到的多个鼬獾狂犬病病毒株在系统发生上也属于ii群.iii群仅见于广西壮族自治区、云南省两地,与东南亚国家狂犬病分离株同源性高达97.7％.iv群的地区分布不规律,在中国东北、中原、东南和西部地区均有零星报道,分离株较少.v群近年来仅偶见于内蒙东北部及黑龙江省与俄接壤地区,与俄罗斯远东及韩国流行株同源性高达98.5％.综上,中国狂犬病流行以犬间传播为主,野生动物狂犬病的流行日益严重,东北和西南地区存在境外狂犬病传入.犬等动物种群免疫覆盖率低应是狂犬病持续传播的主因.

EPIDEMIOLOGICAL CHARACTERIZATION OF RABIES VIRUS ISOLATES IN CHINA BY PHYLOGENETIC ANALYSIS

The phylogenetic tree of Rabies virus(RABV) isolates was constructed based on their full-length nucleoprotein gene sequences to illustrate epidemiological features in China.The results showed that 62 RABV isolates from 17 provinces all belonged to genotype 1 and were further divided into 5 genogroups(i to v).The intragroup homologies of the nucleotide sequences were 91.4 to 99.9%,whereas the intergroup homologies of the nucleotide sequences were 84.5 to 90.1%.The majority of isolates were classified into genogroups i and ii.Isolates in genogroup i,most from dogs,were found in all over major epidemic areas while isolates in genogroup ii were mainly collected from southern China,including ferret bagders.Isolates in genogroup iii originated in Guangxi and Yunan Province and shared about 97.7% homology with isolates from Southeast Asian countries.Isolates in genogroup iv scatteredly distributed all over China,and the cases were rarely reported.Lastly,isolates in genogroup v were mainly found in Inner Mongolia and Heilongjiang Province,and shared about 98.5% nucleotide homology with the isolates from Russian Far East and South Korea.In conclusion,dogs remained the main vectors for rabies transmission.The wildlife increasingly involved in rabies epidemics in southern China.In northeast and southwest areas,however,more animal rabies cases were transmitted from neighbouring countries.The low level of population immunity was also considered a contribution to the rabies transmission in China.