Planned exposure to porcine circovirus type 2 by serum injection is not effective at preventing porcine circovirus associated disease

Abstract

Objective: To evaluate the efficacy of injecting serum containing porcine circovirus type 2 (PCV2) or PCV2 antibodies in preventing porcine circovirus associated disease (PCVAD). Materials and methods: Seventy pigs were each randomly assigned to one of 10 groups (n = 7). Two groups per treatment were injected intraperitoneally (Day 0) with saline or with serum collected from pigs at the acute or convalescent stages of PCV2 infection, or from pigs with high levels of passively acquired antibodies. The remaining two groups were vaccinated with an experimental live chimeric vaccine containing PCV types 1 and 2 (PCV1-2). Half of the groups were challenged with PCV2 intranasally and intramuscularly at Day 16 and the remaining groups at Day 35. All pigs were necropsied 21 days post challenge. Results: No significant differences were detected among groups challenged at Day 16. However, among groups challenged at Day 35, less severe lymphoid depletion (P = .04) and lower levels of virus in serum (P < .05) were observed in the group vaccinated with PCV1-2, One pig treated with saline and one treated with serum developed clinical signs and systemic lesions consistent with severe PCVAD. Implications: Under the conditions of this study, serotherapy does not prevent PCV2 infection or development of PCV2-associated lesions or disease in pigs challenged 16 or 35 days post treatment. Pigs treated with serum containing live PCV2 are at risk to develop PCVAD. The live chimeric PCV1-2 vaccine used in this study is effective in controlling PCV2 viremia and minimizing PCV2-associated lesions.