Studies on scrib typhus; tsutsugamushi disease; heterogenicity of strains of R. tsutsugamushi as demonstrated by cross-vaccination studies.

Antigenic differences among strains of R. tsutsugamushi are sufficiently great that vaccines prepared from certain strains fail to induce resistance in mice to infection with other strains. Although the results of cross-vaccination tests indicate varying degrees of relationship between a number of the strains, there is no correlation between source of the rickettsia and antigenic pattern of the agent.