A Reo-like Virus Isolated from Juvenile American Oysters (Crassostrea virginica)

Abstract

SUMMARY A filterable agent, designated 13p2 was isolated from homogenized juvenile oyster tissue inoculated on to bluegill fry (BF-2) cell cultures. The oysters were from a hatchery on Long Island Sound, New York. Successive passages resulted in progressive cytopathic effects (c.p.e.) consisting of discrete plaques containing large syncytia seen within 2 to 3 days in cultures held at 15 °C. The agent was concentrated from supernatant fluids by ultracentrifugation. Negative stained preparations examined by electron microscopy revealed icosahedral particles with a mean diam. of 79 nm. Virus replication in tissue culture occurred at both 15 and 23 °C. Susceptible fish cells in addition to the BF-2 included brown bullhead, Atlantic salmon, guppy embryo and walleye fry lines. Limited c.p.e. occurred in Atlantic salmon heart cells while rainbow trout gonad, rainbow trout spleen and fathead minnow cells were refractory to cytopathic changes. Biochemical and physical characteristics suggested the 13p2 virus belonged to the family Reoviridae. The possibility that this virus is a known reovirus, present only as a contaminant, was ruled out on the basis of serological results and failure of avian or mammalian cells to support its growth. The 13p2 agent may be an undescribed virus. Further investigations concerning the identity of this virus and its capabilities as a pathogen in fish and shellfish are under way.