Isolation of Tettnang virus from Ixodes ricinus ticks in Czechoslovakia.

Three virus strains closely related to Tettnang virus were isolated from nymphs and males of Ixodes ricinus tick in Moravia and Slovakia. The virus isolates were lethal for suckling mice on intracerebral (i.c.) inoculation but the virus titres in the brain were low. The incubation period of 5--12 days in the first mouse passage was shortened to 3 days in further passages. Infection of mice was accompanied by ultrastructural changes in the cytoplasm of neurons. Groups of spherical virus particles 75 to 80 nm in diameter occurred within simple vacuoles.