Reproductive disease experimentally induced by exposing pregnant gilts to porcine parvovirus

Abstract

Porcine parvovirus (PPV) was administered intravenously or intranasally and orally between the 22nd and the 81st days of gestation to 20 pregnant gilts that were free of hemagglutination-inhibiting (HI) antibody for PPV. Gilts were exposed to 1 or both of 2 strains (NADL-7, NADL-2) of PPV and were killed 21 or more days later. Fetal and maternal fluids and tissues collected at necropsy were tested for PPV, viral antigen, and HI antibody. Transplacental infection occurred with 11 of 12 gilts given the mixture of strains NADL-7 and NADL-2 and with the 1 gilt given strain NADL-7 alone, but not with any of the 7 gilts given strain NADL-2 alone. The 8 noninfected litters were comprised of 74 fetuses of which 73 were alive and 1 was dead. The 12 infected litters were comprised of 91 fetuses of which 62 were alive (31 infected) and 29 were dead (26 infected). Virus was isolated from all of the 57 infected fetuses. Viral antigen was detected in tissues of 50 fetuses, including 5 live fetuses and 24 dead fetuses that were laden with antigen. All dead fetuses with a high concentration of viral antigen in their tissues were members of litters of gilts that were exposed to PPV no later than the 42nd day of gestation. Antibody was detected in serums (HI titers 10 through 1,280) of 27 of the 31 live infected fetuses and in serum (HI titer 10) of 1 fetus for which infection was not demonstrated. All serums collected from gilts at necropsy contained antibody (HI titers 320 through 2560) for PPV, but with the exception of isolating virus from 1 uterine lymph node, neither virus nor antigen was detected in maternal tissues.