Epidemiological Status Of Classical Swine Fever In China And Its Control Measures

Classical swine fever (CSF) is a highly contagious and hemorrhagic disease of Suidae, which is caused by Classical swine fever virus (CSFV), a member of the genus Pestivirus of the family Flaviviridae. Although the implementation of statutory vaccination program is effective in control of the disease without major outbreaks, the CSF is still sporadic in China, causing a complicated situation with a huge economic lost every year. The main reason of this situation is the fact that there is, ascribed to no nationwide investigation carried out yet, a lack of systematic and complete research information showing the epidemiological background of the disease in guiding the control efforts.The efficient control or eradication of the CSF depends on the better understanding of overall epidemiological status. With the attempt to discern the overall view of the genetic diversity of CSFV and its distribution in China as well as the correlation of genetic variation with the virus immunization A. a nationwide investigation on ecosystem and molecular epidemilogy of CSFV was carried out as the first of its kind in China. The detailed results demonstrated the current situation that there are still sporadic events rather than outbreaks over the country. Atypical manifestation has become frequent. The casualty at weaning or even suckling pig populations caused by congenital infection and immunization impotency is a main problem while the fatting and breeding pigs are likely more resistant to the virus. But the persistent infection is usually found in breeding herds. B. the tissue specimens of spleens, lymph notes and kidneys of 392 CSF-suspected cases were collected from all over the country and a fragment of the E2 gene of CSFV encoding major immunogenic sites was amplified by RT-PCR directly from 191 of them, which was followed by sequencing. These 191 field CSFV sequence information represented the disease events happened in 31 provinces, autonomous regions and municipalities. The phylogenetic analysis after alignment of the 191 sequences with those of foreign reference strains showed that Chinese CSF viruses were classified into 4 subgroups of two major groups, i.e. subgroup 2.1, 2.2, 2.3 of group 2 and subgroup 1.1 of group 1. Surprisingly the group 2 viruses in each subgroup showed a closely genetic distance to corresponding European isolates and played a predominant role in causing the disease in China, while the group 1 viruses with a very close distance to Chinese virulent strain Shimen isolated in 1945 played a minor role in the epidemic, indicating different sources of CSF transmission in China. The study has eventually resulted in a first national map describing the distribution of different genotypes of CSF viruses in China and thereby a preliminary bank of molecular epidemiology data and variant CSF field isolates was created accordingly. C. In addition, Our study was the first in China describing the application of DNA immunization method to generate monoclonal antibodies against virus, in which two hybridoma cell lines excreting the monoclonal antibodies with the ability to differentiate CSFV from BVDV were achieved by immunizing the Bal/C mice with CSFV DNA vaccine. D. The experimental challenge of pigs vaccinated with traditional hog cholera lapinized virus (HCLV) showed that the current vaccine could elicited effective cross protection against different genotypes of CSF viruses.The clearer epidemilogical status and genetic diversity of CSFV have been demonstrated in our study which showed that the loose movement of pig population in trading is a main reason in triggeringthe transmission of the disease. Furthermore the study also has established a machanism using molecular epidemiology in surveillance of CSF in China. The consequence of our study is not only an important supplement towards understanding the global situation of molecular epidemiology of the virus but also plays a significant role either in control of CSF in China or in establishment of an international surveillance system for the dis...