IXODES-RICINUS - VECTOR OF A HITHERTO UNDESCRIBED SPOTTED-FEVER GROUP AGENT IN SWITZERLAND

Abstract

A tick/rickettsial survey in various parts of Switzerland revealed the presence of a new, hitherto undescribed spotted fever group rickettsia (Swiss agent) in up to 11.7% of I. ricinus collected off vegetation. Infection in ticks was generalized with rickettsiae developing intracellularly and occasionally also intranuclearly. As a result of massive growth in ovarian tissues, including the germinative cells, the rate of transovarian and filial infection was 100%. The Swiss agent appears to be nonpathogenic for guinea pigs, domestic rabbits and Swiss mice, but in male meadow voles (Microtus pennsylvanicus) it produces a microscopically detectable infection in the tunica vaginalis. The rickettsia grows well in tissue culture systems including chick embryo fibroblast, Vero [African green monkey kidney] and vole tissue cells, when inoculated via yolk sac into 5 day old hens'' eggs, it kills 100% of the embryos after 5-7 days. Antigenic relatedness of the Swiss agent to rickettsiae of the spotted fever group was indicated by indirect and direct fluorescent antibody staining. Preliminary serologic typing by microimmunofluorescence and by microagglutination indicated that the Swiss agent differs from all prototype strains of spotted fever group rickettsiae studied so far.