湖南省武岗市洞口县狂犬病流行病学研究

目的分析2003-2004年间在湖南省武岗市与洞口县发生的狂犬病并探讨局部地区流行的因素.方法对狂犬病进行个案调查,用直接免疫荧光法检测犬脑组织中的狂犬病毒抗原,用RT-PCR法扩增N基因片段,测定核苷酸序列并构建系统发生树进行遗传特征分析.结果自1991-2002年武岗市与洞口县仅各报告1例人狂犬病,但2003-2004年间,分别报告30例人狂犬病.62例狂犬病患者中61例被犬所伤,1例被猫所伤.在有完整记录的50例患者中,平均潜伏期为44.18天.其中7例（14%）狂犬病患者的潜伏期≤15天,16例（32%）潜伏期≤20天.在疫点周围采集的99只犬脑组织中,13只犬脑组织狂犬病毒抗原阳性,阳性率为13.13%.将Wg13与Dk13株病毒的部分N基因核苷酸序列与已报道中国病毒株比较,发现2株病毒与广西及安徽的毒株有最高的同源性,构建的系统发生树也分在同一分支.用全N基因核苷酸序列分析发现,Wg13与Dk13毒株全为Ⅰ型狂犬病毒,2株病毒之间的同源性为99.4%以上.比较分析2株病毒N基因编码的氨基酸序列,发现包括第Ⅳ抗原位点区在内的多个氨基酸位点发生了氨基酸的替代.结论引起武岗市与洞口县的狂犬病流行的病毒不是新型狂犬病毒,犬饲养量大与病毒携带率高是狂犬病暴发的直接原因.

An epidemiological study on rabies in Wugang and Dongkou counties, Hunan

Objective To study the human rabies cases occurred in 2003 and 2004 in Wugang and Dongkou areas in Hunan province, and to explore the possible factors causing the epidemics. Methods Each case of rabies was investigated. Brains of the canines were collected, and direct immunofluorescence assay was used to detect rabies virus antigen in the brains. N gene was amplified by RT-PCR, and then sequenced. The phyologenetic trees were constructed to study the genetic characters of rabies virus. Results From 1991 to 2002, only one of the human rabies case was occurred in the area of Wugang or Dongkou but 30 cases of human rabies were reported in the same areas in 2003-2004. Among 62 cases, 61 were attributed to dog bites, and one was reported to be bitten by a cat. Median incubation period was 44.18 days for the 50 cases with clear history records. However, it was noticeable that 7(14%) and 16(32%) of the 50 cases developed the disease within 15 days and 20 days after the exposure. A total of 99 dog brains were examined for rabies viral antigen by IFA, and 13(13. 13% ) showed positive. Data from the sequences of partial N gene on 2 isolates of the rabies virus showed that they had high homology with the known isolates from Guangxi and Anhui. The phylogenetic tree constructed with the entire N gene sequence showed the two isolates were rabies virus and the homology of nucleotides sequences between the two isolates were 99.4%. They also had 86.1 %-89, 1 % nucleotide sequence identity with vaccine strains, CTN, aG and PV. When comparing the deduced amino acid sequences of the two isolates, some amino acid residues, including the residues in the antigenic site IV , were substituted. Conclusion The virus caused the outbreak in Wugang and Dongkou did not seem to be a new type of rabies virus. The increasing number of dogs and the high rate of dogs carrying the virus might be responsible for the rabies outbreaks.