Effects Of Porcine Circovirus Type 2 And Porcine Reproductive And Respiratory Syndrome Virus Co-Infection On Pigs

In this study,28-day-old piglets were inoculated with porcine circovirus type 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSV), concurrent PCV2 and PRRSV(PCV2/PRRSV), respectively and examined for Clinical symptoms, macroscopic lesions, histologic lesions and Immunohistochemistry for antigen, the distribution and number of CD4+, CD8- T cells in superficial inguinal.Clinical symptoms showed infected piglets appeared deprementia, progressive weight loss.Gross examination included lymph nodes oedema/haemorrhage, lung oedema in all infected piglets. But PRRSV and PCV2 co-infection caused more severe injury than either PRRSV or PCV2 infection alone.Histopathology changes in both PCV2 and PCV2/PRRSV-inoculated pigs were consisted of lymphoid depletion and intracytoplasmic inclusion bodies within histiocytes, bronchointerstitial pneumonia and granulomatous inflammation in lung, but the injury of PCV2/PRRSV-inoculated piglets more severe than PCV2. PRRSV-inoculated pigs had lymphoid depletion and proliferative interstitial pneumonia but did not develop inclusion bodies or granulomatous inflammation.Location of PCV2 in PCV2 group and PCV2/PRRSV group showed that positive signals appeared in macrophages in lymph node, pulmonary macrophages and renal tubular epithelial cells. Location of PRRSV in PRRSV group and PCV2/PRRSV group showed that positive signals appear in macrophages in lymph node, pulmonary macrophages. PCV2 antigen intensity of the PCV2/PRRSV group is higher than PCV2 group, while there was no obvious difference of PRRSV antigen intensity between the PRRSV group and PCV2/PRRSV group.The changes of CD4+, CD8+ producing cells of superficial inguinal lymph node showed that both CD4+ and CD8+ producing cells in the infected piglets were less than the control, but CD4+, CD8+ T cells in the PCV2/PRRSV were lower than any groups.The results indicated that PCV2 but not PRRSV induced the inclusion bodies formation, granulomatous inflammation characteristic of PMWS. PRRSV and PCV2 co-infection could promote the replication of PCV2, but not replication of PRRSV. PRRSV and PCV2 co-infection may cause more severe immunosuppression than either PRRSV or PCV2 infection alone.