Many studies have confirmed that TTSuV1 infection is linked to porcine circovirus 2 (PCV2) infection and promotes porcine dermatitis and nephropathy syndrome. In a gnotobiotic piglet infectionmodel, TTSuV1 promotes both PCV2 and porcine reproductive and respiratory syndrome virus (PRRSV) infections. PCV2 infection without manipulation does not cause clinical signs or post-weaning multisystemic wasting syndrome (PMWS), whereas, when PCV2 infection is combined with TTSuV1 infection, PMWS is produced. In addition, TTSuV1 co-infection with PRRSV is correlated with the development of porcine dermatitis and a nephropathy-syndrome-like condition in gnotobiotic pigs. Zhang et al. (2012) have found that TTSuV1 naturalinfection has an adverse effect on the development of hostimmune responses, suppresses immunization of PRRS MLVvaccine, and prompts PRRS exacerbation in pigs.