A Persistent Hog Cholera Viremia in Young Pigs. ∗

Abstract

Summary

A persistent hog cholera viremia was produced in pigs from non-immune mothers that were 6 weeks of age, but not in pigs that were 3 months of age or in pigs from immune mothers that were 6 weeks of age. Although a similar condition of immunological tolerance has been reported for other animals, it was produced either in utero or shortly after birth. These pigs, therefore, appear unusual because persistence of virus was established at an older age. Pigs with persistent viremia failed to grow and showed elevated temperatures but survived for periods from 6 to 17 weeks. During this interval, persistent virus reverted to a fully virulent state. When they became moribund, virus titers of spleens from stunted pigs ranged from 10⁷ to 10⁹ in contrast to 10⁵ found in spleens from moribund pigs infected with virulent virus in the usual manner. The ability of hog cholera virus to transmit in utero and to persist in pigs after birth may have epidemiological implications.