PCV2 infection increased barrier permeability and SS2 translocation. A Construction of an epithelial barrier model in vitro using STEC. The electrical resistance increased from day 2 to day 8 and formed tight cellular connections. B PCV2 infection decreased the TEER and increased the permeability of the epithelial barrier. STEC monolayers were infected with PCV2 for 24 h, 36 h and 48 h, TEER was measured and was shown relative to the TEER before infection. C PCV2 infection contributed to translocation of SS2 across the tracheal epithelial barrier. The in vitro epithelial barriers were infected with PCV2 for 36 h or 48 h before incubation with SS2 for 2 h, and the number of SS2 penetrating across the epithelial barrier model were counted. D Coinfection increased the barrier permeability compared with the SS2 infection alone. STEC monolayers were uninfected or infected with PCV2 for 36 h or 48 h before incubation with SS2 for 2 h, TEER was measured and was shown relative to the TEER before infection. The results are described as mean ± SD of three independent experiments. Significant differences in B and C were determined using the Student t-test. Significant differences in D were determined using one-way ANOVA analysis. *P < 0.05; **P < 0.01; ***P < 0.001.