In conclusion, we demonstrated that TTSuV1 had high tropism in a wide range of target tissues, especially the immune organs. TTSuV1 DNA load in PRRSV-positive pigs increased obviously from 2 to 5 times in almost all the corresponding parts compared with PRRSV-negative pigs. The detection rate of TTSuV1 in PRRSV-positive pigs was obviously higher than in PRRSV-negative pigs (p < 0.01).All the evidence seems to point to the same conclusion.TTSuV1 may have a synergistic effect with PRRSV, and PRRSV promotes the replication and proliferation ofTTSuV1. Consequently, TTSuV1 should be considered a novel pathogen and should not be ignored. Extensive epidemiological surveillance and pathogenicity characterization of TTSuV1 needs further study.