Identification and survey of Torque teno virus in pigs in China.

Torque teno viruses (TTVs),of the genus Anellovirus,were first isolated from a human hepatitis patient in 1997.TTVs were also identified in several animals,including pigs,cattle,sheep,cats and dogs.In this study,a survey of TTV prevalence was conducted in Guangdong,Fujian,Jiangxi,Anhui,Zhejiang,Henan and Hebei provinces of China.A total of 258 swine sera and tissues were tested by nested-PCR.The results showed that the TTV1 and TTV2 infection rates were 37.6 % and 82.6 % in total,and the co-infection rate was 38.4 %.Some of the untranslated region (UTR) and eight complete sequences of the isolated TTVs were sequenced and compared with the reference strains of TTV1 and TTV2 in GenBank.The results demonstrated that TTV could be segregated into two lineages including TTV1 and TTV2;within our acquired sequences,UTR nucleotide sequence homologies of TTV1 and TTV2 were 80.8 %-98.5 % and 94.2 %-100 %,respectively;compared with the reference strain,UTR homologies of TTV1 and TTV2 were 82.7 %-100 % and 95.5 %-99.1 % at the nucleotide level.In conclusion,our study for the first time provided the evidence that TTV had emerged in pigs in China,indicating TTV might be a very important new pathogen of pigs.