Serological and histopathological responses of rainbow trout, Salmo gairdneri Richardson, to experimental infection with the 13P2 reovirus

Abstract. Both fingerling and adult rainbow trout were given intraperitoneal inoculations of the 131_P2 reovirus which did not result in mortalities but produced a subclinical disease in 56% of the adults and in 65% of the juvenile fish. Sera from virus infected adult trout contained virus neutralizing and precipitating antibodies and demonstrated immunofluorescence of antigen(s) specific for the 13_P2 virus. Virus infection was characterized by increased virus titres and a multifocal reticulo-endothelial granulomatous hepatitis, occasionally accompanied by a fibrosing pancreatitis. Electron microscopy of infected liver tissues demonstrated arrays of 13_P2 virus particles in a reticuloendothelial cell phagosome and in a hepatocyte lipid inclusion body from one of three juvenile fish examined. These results show that 13_P2 virus inoculation of rainbow trout causes a non-virulent virus infection accompanied by specific humoral antibodies. These antibodies are sufficient in titre for use in future serologic studies of the virus. Further discussion regarding the pathogenesis of this virus in bluegills versus rainbow trout is presented.