The isolation and partial characterization of a highly pathogenic herpesvirus from the harbor seal (Phoca vitulina)

This report describes the first isolation and partial characterization of a herpesvirus from the harbor seal (Phoca vitulina). The virus was isolated during a disease outbreak in a group of young seals nursed in a seal orphanage in The Netherlands. Almost half of the seals died with symptoms of acute pneumonia and focal hepatitis and the virus was isolated of organs of most of the dead animals. Seven out of ten seals of which paired serum samples were obtained showed seroconversion in a virus neutralization test during this outbreak. The virus was tentatively characterized as a herpesvirus (seal herpesvirus: SeHV or phocid herpesvirus 1) on the basis of its characteristic morphology in electron microscopy, buoyant density in sucrose, sensitivity to ether and heat treatment and its antigenic relationship with other probable members of the Alphaherpesvirinae subfamily. The virus caused cytopathic changes within 24 hours after inoculation in seal kidney cells, consisting of a focal rounding of cells and syncytium formation. No cytopathic changes were observed in the cells of nine other mammalian species tested.