Vaccination of dams increases antibody titer and improves growth parameters in finisher pigs subclinically infected with porcine circovirus type 2.

Porcine circovirus type 2 (PCV2) is the obligate infectious agent in postweaning multisystemic wasting syndrome (PMWS) of pigs. To control PMWS, we vaccinated dams at 4 and 2 weeks before pregnancy and again in the 12th week of gestation with an inactivated PCV2 vaccine (Circovac). Two producer farms run under the control of Swiss Swine Health Organization were selected for the experiment. Previously, in one farm PMWS was diagnosed on pigs after weaning, whereas in the other farm, pigs wasted during the fattening period. For the experiments 113 dams were randomly vaccinated, and 111 dams were sham injected. Vaccination increased serum antibodies in dams 3- to 9-fold, accompanied by serum antibody titer increases in their offspring. In the sixth week of life, progeny from vaccinated dams had about the same IgG antibody titers as progeny of unvaccinated dams at the third day of life. In sera of vaccinated dams only low concentrations of PCV2 DNA were detected, and no progeny developed PMWS. Interestingly, at day 56 four progeny of unvaccinated dams tested positive for anti-PCV2 IgM antibodies, indicating a primary infection with PCV2. Of economic importance is the observation that progeny of vaccinated dams had a significantly higher daily weight gain in the fattening period (farm X, +51 g/day; farm Y, +30 g/day) and thus a shortened fattening period of about 6 days compared to progeny of controls. To our knowledge this is the first demonstration of subclinical circovirus infection and its effects on growth performance of fattening pigs by vaccination of dams.