Abstract: To investigate the infection of Torque teno virus (TTV) in pigs in Guangxi,a total of 156 samples of blood, aborted fetuses, lungs, spleens, kidneys, livers and lymph nodes from 140 farms were detected by Nest-PCR. Cloning, sequencing and genetic evolution analysis were conducted on the UTR in positive samples, some of which were also detected for porcine circovirus 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSV), classical swine fever virus (CSFV) and pesudorabies virus (PRV), followed by separation and identification of bacteria. The findings were that the total infection rate of TTV was 93.6%, in which the infection rate of TTV2 reached 76.9%, not only being remarkably higher than that of TTV1 (16.7%) but also with higher genetic variation among strains. TTV generally mixed with PCV2 and PRRSV, and the rate of mixed infection with PRRSV was higher (64.29%). There were double, triple or even quadruple TTV mixed infection with other viruses in pigs. Clinically, more Streptococcus pneumoniae and Haemophilus parasuis were detected in mixed infection (or secondary infection) of TTV and bacteria. This study proved that there were TTV infection among swines in Guangxi,and PRRSV,PCV2 and CSFV were more commonly seen in such mixed infections.

Key words: Torque teno virus(TTV); mixed infection; investigation and analysis