Duration and biological half-life of passively acquired colostral antibodies to porcine parvovirus.

The duration of passive immunity and biological half-lives of passively acquired antibodies to porcine parvovirus (PPV) were determined in 4 pigs from each of 10 litters. All sows were randomly selected from a herd naturally infected with PPV. At parturition, blood and colostral samples from the 10 sows contained hemagglutination-inhibiting (HI) antibodies to PPV; the HI titers of colostrum were about 5 times higher than that of serum. The HI antibodies in serum and colostrum of sows were resistant to 2-mercaptoethanol, indicating that antibodies were of immunoglobulin G class. Pigs were allowed to suckle, and their blood samples were collected at 2 days of age and every 2 weeks thereafter. At 3 to 4 weeks of age, pigs were weaned and moved to an isolation facility. All pigs had HI antibodies to PPV at 2 days of age. Passively acquired antibodies steadily decreased from the circulation of pigs, and the rate of antibody decrease was similar in all pigs. Antibodies to PPV persisted for about 16 to 24 (mean 21.2) weeks, and all pigs were seronegative at 26 weeks of age. Pigs were susceptible to experimental infection with PPV as early as 1 week after they became seronegative. The biological half-lives of antibodies to PPV, unadjusted and adjusted for body weight gain, were determined to be approximately 19.7 and 29.0 days, respectively.