Epidemiology Of Rabies In Hunan Province During 1988 To 2007

Objective:By analyzing the epidemiological characteristics of human rabies in Hunan province in recent twenty years, this study explores the factors that affect incubation period and incidence of rabies, in the hope to provide a scientific basis for strategy making to control and prevent the disease.Methods:Collecting data from the notable epidemic situation report from 1988 to 2007 in Hunan province with a descriptive epidemiological study later employed. The total 1,059 individual cases from 2004 to 2007 were input into database with Epidata3.1 software, and subsequently a nonparametric 1 analysis based on both Mann-whitney U test and Kruskal-Wallis test was made on incubation period factors with software SPSS 13.0, while a non-conditional logistic regression analysis was targeted at the factors of post-exposure rabies vaccination.Results:Over the past 20 years (from 1988 to 2007), a total of 4,401 human rabies cases were reported in Hunan province, with an annual average incidence rate at 0.35 per 100 thousand population. The epidemic situation had a "V" shape distribution trend-former ascend and later descent. The majority of cases were distributed to south and middle areas of the province, though each of the 14 cities had their own cases. Five cities such as Yongzhou, Chengzhou, Shaoyang, Hengyang, Huaihua totally reported 2,378 cases, accounting for 54.03%. Most of the cases were occurred between June to October, while fewer occurred from February to April. The most susceptible group were farmers, secondly were students, with the constituent ratio of 61.21% and 18.95% respectively. The age group from 5 to 9 years took the most cases, followed by 10 to 14 years group and 65 to 69 years group. The median of the incubation period was 56 days (the minimum and maximum incubation period was 2 and 2,706 days respectively). The clinical course of disease was 0 to 13 days, with a median of 3 days. Statistical analysis based on Mann-whitney U test and Kruskal-Wallis test showed that the incubation period was statistically link to such thirteen factors as ages, occupation, the degree of exposure, exposure sites, wounds treatment, wounds scouring, wounds disinfection, wounds suture, post-exposure human rabies vaccination injection, pre-exposure immunization, animal kinds, animal sources, reasons of bitten by animals. Further statistical analysis demonstrated that three factors including degree II of exposure (OR=0.450,95%CI0.247-0.820), wounds untreatment (OR=0.365, 95%CI 0.173-0.768), wounds treatment with other methods were protective factors of post-exposure vaccine injection. While wounds treatment in medical (OR=31.467,95%CI13.839-71.550), wounds scourring(OR=2.300,95% CI 1.145-4.622), wounds suture(OR=2.556, 95%CI 1.090-5.993) exposure sites were risk factors.Conclusions:After a decline period from 1988 to 1996, human rabies in Hunan province demonstrated an ascending trend once more in recent years, posing a serious threat to people's life and health. Low immune-vaccination of home dogs,, poor quality of vaccine, nonstandard and untimely treatment, lacking of collaboration were considered causes of the rabies. It suggests that main measures for control and prevention of human rabies be strengthened on health education among high-risk group in rural areas, post-exposure wound treatment and vaccination infection. Objective:To find out the infection status of domestic dogs infected by rabies viruses, and further establish a diagnosis technique platform, providing a scientific base for human rabies control and prevention.Methods:During November 2005 to January 2006,5 counties (Lengshuitan, Shaodong, Taoyuan, Xiangxiang and Luxi county) representing high, middle, and low incidence were selected with stratified sampling. The brain tissue samples of healthy-looking domestic dogs sold on agricultural markets were collected with random sampling by local CDC members. The samples covered insteadly from fourteen counties in whole province from April 2007 to March 2008. These samples were later detected for rabies virus antigen by direct Immunofluorescence assay (DFA) and further for the specified nucleotide with nested RT-PCR.Results:A total of 1,613 samples from the brain issues of domestic dogs were detected from 2005 to 2008 in Hunan province, with 80 positive cases by DFA and 67 confirmed by nested RT-PCR as a result, and the infection rate of the domestic dogs with the rabies virus was 4.15% in Hunan province. The infection rate of the healthy-looking domestic dogs with the rabies virus was 3.80% in Hunan province in 2005, followed by five surveillance areas respectively at 1.83% (Lengshuitan),7.24%(Shaodong),5.88%(Taoyuan),2.63% (Xiangxiang) and 1.97%(Luxi), which was statistically different (χ2=9.673, P<0.05). The infection rates were 26.87%,13.83%, 10.42%,6.94% respectively in four regions including Shaoyang county, Xiangxiang city, Chalin county and Lanshan county, no positive results were found in the rest 10 counties. There was statistical differences in infection rate of domestic dogs among different regions (χ2=33.846, P< 0.01), those from Shaoyang city, Yongzhou city and Xiangtan city all showed a relative high level.The infection rate of male domestic dogs was 4.68%, and that of female was 2.85%, with no significant difference(χ2=2.556, P>0.05). The infection rate of domestic dogs with big body size was 4.57%, with no significant difference among them (χ2=1542, P> 0.05), from that of medium size 3.02%.The infection rate between juvenile and adult group was 4.95%and 1.57% respectively and statistically different (χ2=11.133, P<0.05). Two figures of 1.29%,4.63%(χ2=4.762, P<0.05) were statically-different and belonged to verterinary rabies vaccination doing and undoing, while figures of 9.56%,7.53%,2.31%,3.23%(χ2=22.254, P<0.01) belonged to four seasons from spring to winter respectively.When it comes to relationship of rabies between infection rate and incidence rate, both the infection rate of rabies virus during 2005 to 2006 in the surveillance areas had positive correlation (Pearson r=0.796, P=0.047) with the incidence rate of human rabies from the surveillance areas in 2006 and also in 2007-2008 as study results showed(Spearman r=0.900, P=0.019).Conclusions:The domestic dogs in Hunan province carried a high level infection rate of rabies virus. Furthermore, they linked a positive correlation with the incidence rate of human rabies within the province. Therefore, it's necessary to enhance the immunization and strict control over dogs so as to stop the rabies epidemic. Both DFA and nested RT-PCR were proved to be a pretty sound tool on rabies virus epidemiological investigation. Objective:To find out characteristics of rabies virus on types, geographical distribution, variation and dynamic evolution, and provide evidences for effective prevention and control measures.Methods:Based on strains from five areas representing three different incidence rate level areas at high, average and low, N genes located within were sequenced, followed by a series of molecular epidemiology study such as inner sequence alignment analysis of both nucleotide and amino acid, inner phylogenetic analysis. Then, for outside molecular epidemiology comparisons, sequences of nucleotide and coded amino acid based on the N genes were compared to those from historical rabies virus strains, rabies vaccine strains home and abroad, typical strains home and abroad with such DNAstar software.Results:All 20 rabies virus isolated from Hunan province belonged to genotype 1 in 2006. In terms of sequence identity, the neucleotide of N genes ranged from 88.8%-100%(averaging at 98.1%), compare to that of coded amino acid 99.2%-100%(averaging at 99.6%). These strains were phylogenetically divided into three groups (A,B,C), showing a geographic distribution.We found that the research strains enjoyed the closest relationship with CTN strain, one China rabies vaccine strain, with a sequence identity of 89.9%-94.2%(averaging at 90%) among those vaccine strains from home and abroad. When compared to typical strains nationwide, the rabies strain under research enjoyed a closer genetic relationship with its neighbor provinces such as Guizhou, Hubei, and Guangxi, second by slight far provinces such as Jiangsu and Henan. Phylogenetically anlysis of this group research strains also resulted in two goups, one mainly limited to east China, while the rest limited to west China. In comparison with those abroad typical strains, two groups were also found out, demonstrating all 20 strains under research belonged to the same group, sharing the closet genetically relationship with Indonesian strains at same branch, while a relative far genetically relationship with those from other areas of Asia, Africa, America and Europe countries.Conclusions:All 20 rabies viruses isolated from Hunan province belonged to genetype 1. The nucleotide and amino acid sequence of of N genes had high identity among Hunan province rabies virus strains, and they enjoyed a closer genetic relationship with its neighbor provinces and far provinces. They also shared the closer genetically relationship with Indonesian strains at same branch, while a relative far genetically relationship with those from other continents. The virus islolated from Hunan province presented a unique characterization of geographic distribution. The research strains enjoyed the closest relationship with CTN strain, it seemed to be a great potential effectiveness to used CTN strain in Hunan province.