Molecular Epidemiology Of Wssv Viruses In Zhejiang Province

White Spot Syndrome virus (WSSV), Taura Syndrome virus (TSV) and Infection Hypodermal and Haematopoietic Necrosis virus (IHHNV) are three emerging aquatic viruses responsible for major economic losses in shrimp culture industry.Shrimps samples were collected from 12 farms in Zhejiang province, China, during 2008 and analyzed by PCR or RT-PCR methods to determine the prevalence of these viruses.Among these sampling farms, samples from all farm showed indication of infection with WSSV or IHHNV, four were detected high ratio of co-infection with these two viruses in one individual. samples from 2 farms exhibited evidence of infection with WSSV only, and samples from 4 farms just infected with IHHNV only. Surprisingly, no samples exhibited evidence of infection with TSV, the results show that through years of efforts to prevent and control, TSV incidence rate has fallen to very low levels in Zhejiang Province. The high prevalence of WSSV and IHHNV viruses in adults implying that the viruses were transmitted to shrimps during their cultured environment and inappropriate breeding management. Our study would remind the farmers to take strict quarantine control for virus infection during the breeding.WSSV has different genotypes which were usually characterized by major variable loci in the genome, mainly including variable region ORF23/24, variable region ORF14/15 and variable number of tandem repeats (VNTR) in ORF94. In this part, WSSV strains collected from Zhejiang provinces of China from 2008 were analyzed by PCR amplification and sequence analysis. In our samples, we identified 3 genotypes which show gradually increasing sizes of deletions in variable region ORF23/24 and ORF14/15. Respectively, they contained 5657 bp, 11093 bp and 10977 bp deletions. Our study still notes that the repeats of ORF94 are highly variable in numbers. Surprisingly, we found that WSSV isolates from 3 farms deleted this region absolutely.Furthermore,The genotypes WSSV08JJS was amplified and can be used for further virulence comparison.Our epidemiologic data are helpful for local farmers and government agencies to asses the risk of viral pathogens to shrimp populations within a particular region, determine priorities and develop diseases control strategies.