BIOLOGIC AND GENETIC CHARACTERIZATION OF AN INFLUENZA A VIRUS ASSOCIATED WITH EPIZOOTIC PNEUMONIA IN SEALS

Abstract

An influenza A virus antigenically similar to A/FPV/ Dutch/27 (Hav1Neq1) was isolated from harbor seals (Phoca vitulina) that had died of acute hemorrhagic pneumonia on Cape Cod Peninsula, USA, in the winter of 1979-1980. High titers of virus were obtained from the lungs and lower titers from the brains of the seals. Antigenic and genetic analyses of the seal isolates showed that all of the genes and gene products were closely related to different avian influenza viruses; however, biologically, the virus behaved more like a mammalian strain. The seal virus replicated and produced pneumonia in experimentally infected harbor seals, but the clinical course and pathology were less severe than in the natural infection. The virus also replicated in ferrets, cats and pigs but produced no disease. In avian species, the seal influenza virus replicated poorly, produced no disease signs and was not shed in the feces. During studies with experimentally and naturally infected seals, several individuals experienced conjunctivitis and high titers of seal virus were recovered from the eye of one individual, indicating that this virus can infect the human eye.