Methods of Artificially Inducing Erythrocytic Inclusion Body Syndrome in Coho Salmon

Abstract

Methods for artificially inducing erythrocytic inclusion body syndrome (EIBS) in cohosalmon, Oncorhynchus kisutch, were studied. Healthy coho salmon (B.W.7-8g) were injectedintraperitoneally or bath challenged with filtered homogenates of blood, spleen, head kidney, or excrement from naturally infected fish. The syndrome was induced by both injection andbath challenges. Artificial infections were obviously induced at temperatures of 8-10°C and there was a high incidence of fish with erythrocytic inclusions and low hematocrits. At 8-10°C, inclusion bodies appeared most frequently 3 weeks after injection, while they were most prevalent 4 weeks after bath challenges. Hematocrits decreased to 8-12% approximately 4-5weeks after injection when fish were held at 8-10°C. Blood homogenates of substantiallyinfected fish with red blood cells with inclusions were more effective than those from moribund fish without inclusions and were able to infect fish when diluted 10, 000 times by injectionor 1, 000 times by bath challenges.