A field trial on efficacy of killed PCV-2 vaccine in decreasing pathological lesions

Abstract

Suvaxyn® PCV2 (Fort Dodge Animal health, USA) is the Chimeric PCV1-2 vaccine containing immunogenic capsid gene cloned of PCV2 into the backbone of the nonpathogenic PCV1. The objective of this study was to investigate the efficacy of Suvaxyn® PCV2 on decreasing pathological lesions and PCV-2 viremic condition in a PCVAD-affected herd in Thailand. A PCVAD-affected herd (3,200-sow herd) was selected by previous history, necropsy reports and serology. Two hundred 3-week-old weaners were equally divided into two groups: A and B. At 4 weeks of age, group-A pigs were vaccinated with 2 ml of Suvaxyn® PCV2 vaccine, whereas, pigs in group B were injected with 2 ml of normal saline. Serum samples were collected from 20 pigs per group at 4, 5, 7, 9, 12 and 15 weeks of age for serological examination (2 pigs/pen), and polymerase chain reaction (PCR). The average serological titers were high at 4 weeks of age and then declined at about 5 weeks in both groups indicating the waning of the maternal derived antibodies between 5 and 7 weeks old. The seroconversion was observed in vaccinated pigs at 9 weeks of age suggesting of vaccination-induced antibody titers. In non-vaccinated pigs, PCV-2 seroconversion was detected at 12 weeks of age, probably due to the natural PCV2-infection after weaning. None of PCV2 DNA was detected in vaccinated pigs before 15 weeks of age, while it was detected in the sera of non-vaccinated pigs at every time point. The average of lymph node/body weight ratio in vaccinated pigs (38.5x10̄⁵) was lower than those in non-vaccinated pigs (45.4x10̄⁵), but it was not statistically significant. Histopathologically, lymph nodes had less severe lesions in the vaccinated pigs. The results suggest that Suvaxyn® PCV2 is able to induce PCV2 antibody and subsequently, reduce PCV2 viremia and pathological lesions.