Abstract
Experimental oral infection of rainbow trout Salmo gairdneri with multinucleate spherical bodies of Ichthyophonus hoferi cultivated was carried out. Rainbow trout orally injected with thick walled multinucleate spherical bodies cultivated in MEM containing 10% fetal bovine serum showed 100% infection and 90% cumulative mortality at 16°C water temperature for 25 days. However, those orally injected with spherical multinucleate hyphal terminal bodies cultivated in TGC containing 1% rainbow trout serum showed no infection and no cumulative mortality. The former showed the same symptoms such as darkness of the skin colour, perforation in the body surface and/or nodular white spots in several internal organs and so on as in the naturally infected fish. Amoeboblasts which underwent endogenous cytoplasmic cleavage were also observed in the liver of the rainbow trout infected artificially.
