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The objectives of this study were to determine if co-infection of piglets with PRRSV and PCV2 has any affect on PCV2 shedding characteristics and if there are differences in shedding patterns between PCV2 subtypes (PCV2a and PCV2b) in co-infected pigs. Materials and methods Twenty-three, 2-to-6-week-old, PCV2 and PRRSVnaïve pigs were randomly assigned to one of five groups according to Table 1. able 1. Experimental design. Group n Inoculation PCV2 PRRSV Negative 3 - - PCV2a-I 5 PCV2a - PCV2a-PRRSV-CoI 5 PCV2a PRRSV PCV2b-I 5 PCV2b - PCV2b-PRRSV-CoI 5 PCV2b PRRSV PCV2 inoculation was done using PCV2a strain 40895 and PCV2b strain NC16845. For PRRSV inoculation, PRRSV strain VR2385 was utilized. Blood was collected on a weekly basis and tested for presence of anti-PCV2 antibodies by a PCV2 ELISA (5) and for presence of PCV2 DNA (6) and PRRSV RNA by PCR. Oral, nasal and fecal swabs were collected in regular intervals from day post inoculation (dpi) 0 until dpi 70 and tested by quantitative real-time PCR for the presence of PCV2 DNA. All pigs were necropsied at dpi 70.
Negative control pigs remained PCV2 and PRRSV negative for the duration of the study. All pigs infected with PCV2 became infected as evidenced by PCV2 viremia and seroconversion. There was a significantly (p< 0.05) higher load of PCV2a and PCV2b DNA in serum, oral swabs, nasal swabs and fecal swabs in pigs concurrently infected with PCV2 and PRRSV compared to pigs singularly infected with PCV2 further confirming that PRRSV enhances replication and shedding of PCV2. Moreover, PRRSV infection significantly (p<0.05) prolonged the presence of PCV2 DNA in serum and increased the amount of PCV2 DNA in oral and nasal secretions and fecal excretions in the later stages of infection between dpi 28 and 70. Shedding patterns were similar between groups infected with PCV2a and PCV2b, indicating that there was no PCV2 subtype-specific interaction with the PRRSV isolate used in this study.
T. Opriessnig, A. Sinha, N. Beach, Y. Huang, X.J. Meng, P. Halbur. PRRSV enhances PCV2a and PCV2b replication and duration of shedding. 6th International Symposium on Emerging and re-emerging Pig Diseases: 41
