Epidemiology Of Animal Rabies In China, Isolation And Characterization Of The Street Virus

Rabies is a zoonotic disease, Every infected bodies almost died. In the developed country, human rabies had disappeared and canines have not been disease transmitter. Chinese rabies cases is the second for the world, especially the number exceeded 2000 cases from 2002. Rabies is the main disease in hazard the public health security. Surely, the reasons are larger number dogs in our country and lower immuno fraction of coverage. Additionally, the seriously problem which we do not know the virus distribution and genetic background, sensitivity animals'infected situation is more and more clearly. The epidemiology data come from part of China told us, 93% to 100% human cases is caused by the canine, the second transmitter is cat. It is very important to investigate the epidemic area of rabies, isolate and identify field variants. Based on these, we can get the reference about Chinese variants distribution and phylogentic relationship. All of these will contribute to prevent and control the rabies.Collection samples is the first step to start the epidemiology study. The procedure must obey the rules of sample collection. We defined the southern China which are rabies epidemic areas as main regions to study and dog is the investigated animal. During the study period, the number of healthy canine brain samples is 1431 which came from 12 regions belonging to 3 provinces or cities, saliva samples is 545 which came from 9 regions of Guangdong province, serum samples is 405 which came from 11 regions of Guangdong and Hunan provinces, part of them (214) are immuned canine's serum. Except these samples, we gathered the clinical suspecting animal's brain, the batch number is 78, including canine's 70, 3 cow's, 2 goat's and 3 pig's, the samples came from 15 regions of China. When we do the collection, we setup the record system and registered the details of samples about epidemiology, such as the sensitivity animal's population, the situation of rabies in the area, animal's immune record and health situation. The system will be very useful for the further study.RABV is the prototype species of the genus Lyssavirus in the family Rhabdoviridae, it contains nonsegmented, negative-sense, single-strand RNA genomes. One of the five structure gene—N gene, coding nucleocapsid protein of the virion, have the character of conservation and high copy during the replication, became the base of Lyssavirus genotype and target sequence in molecular diagnosis. Although the street virus isolated from China are all belong to the genotypeⅠ, we worried about other genotype RRV existing in China for the Europe and Asia continents connection. Thought about these, we setup test protocol based on the RT-PCR for the RABV detection. The sensitivity test results showed the method can detect 0.2 TCID50 cell-culture RABV, and 100 times sensitivity compared with the MIT. The other experiments proved that the protocol can amplify the seven genotype LV, and the good results gotten from the canine, cow, swine and bat brains test. After the trial test in the veterinary CDC, we drafted the procedure standard--<>.The policy of World health organization about the prevent and control rabies advise the effective prevention should be setup after the fraction of coverage arrived to 70% of immuned canine. We tested canines serums came from Guangdong and Hunan province by FAVN, and get the data of RABV neutralization antibody level. Then we can reach the discussion about evaluation vaccine used in the canine and know the infected situation of healthy dog. The results showed, the healthy infected rate is 8.74% (9/103); the positive rate of antibody level in pet dog is 31.25% (10/32), house dog is 29.67% (54/182). The discussion is the vaccine of Guangdong province is not checkout.Through etiology examination, we have isolated animal RABV variants, simultaneously collected molecular epidemiology evidence, found out local dogs and domestic animals carrying virus situation, thus partially promulgates our country RABV popular virus heredity background, established the virus strain epidemic information database, all these will provide the basis for the future tracing virus transmission and the forecast epidemic possibility. In the end, we obtained rabies field variants 22, including dog source strains 18, cow's 3, pig's 1, distributes in 6 provinces and the municipality. 30 animal source RABV N gene subsequence were obtained. The Chongqing healthy dog has been tested all negative, the positive rate which the Hunan healthy dog brains is 1.01% (2/198), the Guangdong sample is 0.33% (4/1221), the saliva sample is 0.55% (3/545). These results indicated that we should strict management the dog group to prevent rabies.Phylogentic analysis about Chinese animal RABV variants is based on 30 N gene sequences of our isolates and reference sequences of LV signed in the GenBank. Through the compare sequence, we can get the result of evolution position of Chinese animal RABV, the relationship between Chinese variants and fixed strains, other countries'field strains. The results showed that, all the isolated strains belong to the genotypeⅠand there are no other genotype LV in China. The lowest percent identify of the 30 strains is 81.5% on the nucleic acid and 91.8% on the amino acids. The differential strains come from special region have clear vary site on the N gene and N protein. Further analysis showed, these strains can be partitioned four evolution groups and Chinese animal strains should be five groups, our strain belong to the four of five groups. Compared with world variants and the tree showed the 3 groups connected with the different continents, Chinese variants have clearly region character in the map. Another results is Chinese vaccine strains, CTN and ERA, have close relation with Chinese variants and they can induced the body immune reaction to resist the field strain attack.