Viral Hemorrhagic Septicemia: Comparative Susceptibility of Rainbow Trout (Salmo gairdneri) and Hybrids (S. gairdneri × Oncorhynchus kisutch) to Experimental Infection

Abstract

Rainbow trout (Salmo gairdneri) fry and yearlings were compared with hybrids of rainbow trout and coho salmon (Oncorhynchus kisutch) for susceptibility to viral hemorrhagic septicemia (VHS). In three trials, exposure to waterborne infectivity consistently resulted in a 77% mortality of rainbow trout fry while loss among the hybrid fry averaged only 11%. Tests showed survivors might be carriers of virus. Hybrid yearlings infected by gill brushing were fully refractory to VHS whereas mortality (3:8) and viremia were recorded among gill-infected rainbow trout yearlings.