Title : Evaluation of pathogenesis of concurrent SIV and PCV 2 infection in CD /

The objective of this project were to investigate the pathogenesis of an H1N1 (not pandemic H1N1) swine influenza infection in pigs subclinically infected with porcine circovirus type 2b (PCV2b). Forty caesarean-derived, colostrumdeprived (CD/CD) pigs were randomly assigned to four groups, 10 pigs per group. Group 1 pigs served as shaminoculated controls, Group 2 pigs were inoculated with SIV, Group 3 pigs were inoculated with PCV2b and SIV, and Group 4 pigs were inoculated with PCV2b. Pigs were inoculated intranasally with PCV2b at 4 weeks of age (study day 0) and SIV pigs were inoculated intra-tracheally at 6.5 weeks of age (study day 17). Dual-infected pigs had increased (p < 0.05) clinical respiratory scores (dyspnea and cough), shed increased amount of SIV in nasal secretions (p < 0.05), and had a prolonged period of SIV shedding when compared to SIV-only inoculated pigs. Macroscopic and microscopic lung and lymph node lesions were not significantly different between the dual-infected group and the SIV group. Group mean