Porcine parvovirus infection and stillbirth in swine. I. Virus isolation from stillborn piglets (author's transl)

Abstract

A total of 341 stillborn and dead neonatal piglets were collected from 233 sows in the field throughout Japan during a period from 1970 to 1974. Virus isolation was made from the brain and internal organs of these piglets by use of porcine kidney cell cultures and mice.Porcine parvovirus (PPV) was recovered from 31 stillborn piglets of 22 litters and 6 dead neonatal piglets of 4 litters in porcine kidney cell cultures. The dams of these 37 piglets had farrowed some time between August and November every year, except one which farrowed in April. The virus was isolated from almost all the principal organs and placental tissue of infected fetuses. It was onfirmed by a serological survey that all the dams of those 37 piglets had been infected with this virus during the period of pregnancy. A stillbirth rate of farrowed young was 57.2% in 21 sows from which PPV was recovered. The average number of normal young delivered was 4.4 per litter. The average number of abnormal piglets per sow was 5.9. No abnormal piglets showing nervous symptoms were farrowed from these 21 sows. The average gestation period was 113.7 days in these sows.Japanese encephalitis virus (JEV) was recovered from 8 stillborn pigltes of 8 litters and 6 dead neonatal piglets of 5 litters in both cell cultures and mice in almost the same season as PPV. A stillbirth rate of farrowed young was 73.8% in 10 sows which gave birth to young harboring JEV. The average number of normal young delivered was 2.8 per litter. The average number of abnormal piglets per sow was 7.9. Distinct nervous symptoms were manifested by 32 abnormal living piglets farrowed by those 10 sows. The average gestation period was 114.6 days in these sows.From the results mentioned above it was presumed that infection with PPV might be responsible for the occurrence of swine stillbirth. The rate of stillbirth caused by PPV was lower than that by JEV. Nevertheless, it should be emphasized that studies on the distinction of stillbirth by PPV from that by JEV and on the prevention of stillbirth caused by PPV are very important.