Efficacy of a Chimeric PCV2 Vaccine: a Field Trial

Abstract

Field trial of a Chimeric porcine circovirus type 2 (PCV2) (Suvaxyn PCV2®, Fort Dodge Animal Health, USA) vaccine was performed in order to investigate the efficacy on decreasing pathological lesions and PCV2 viremia in a PCV2-affected swine herd in Thailand. A herd was selected based on history and serological data. Three-week-old pigs (n = 200) were equally divided into two groups. At 4 weeks old, the pigs (n = 100) were injected intramuscularly with 2 ml of Suvaxyn PCV2® vaccine and the non-vaccinated pigs were injected with 2 ml of normal saline. Sera were collected from 20 pigs per group at the age of 4, 5, 7, 9, 12 and 15 weeks old for assessing PCV2-specific antibodies and PCV2 genetic material by serology and polymerase chain reaction (PCR) tests. Results of PCV2 specific antibodies revealed high titers at 4 weeks of age and declined at 5-7 weeks old in both groups indicating the maternal derived antibodies. Seroconversion was observed in the vaccinated pigs at 9 weeks of age suggesting antibody response to vaccination. In the non-vaccinated pigs, PCV2 seroconversion was detected at 12 weeks, indicating antibody response to natural infection. The PCV2 genetic material was not detected in the vaccinated pigs before 15 weeks of age, while PCV2 DNA was present in the sera of the non- vaccinated pig at all time points. Postmortem examination (n = 20) at 16 weeks of age revealed that the histopathological lesions of the lymph nodes of the vaccinated pigs were less severe than those of the non-vaccinated pigs. The average of lymph node/body weight ratio in the vaccinated pigs was lower than those in the non- vaccinated pigs, but was not statistically significant. The results suggest that Suvaxyn PCV2® was able to induce PCV2-specific antibodies and subsequently reduced PCV2 viremia and PCV2-associated pathological lesions.