Isolation of Coxiella burnetii and of an unknown rickettsial organism from Ixodes ricinus ticks collected in Austria.

Two strains of Coxiella burnetii and two strains of an unidentified rickettsial organism were isolated for the first time from Ixodes ricinus ticks collected in the Alpine region of Tirol, Austria. The C. burnetii strains belong to the group of agents causing acute forms of Q fever. The other two strains of isolated rickettsial agent share some antigenic epitopes with C. burnetii and R. prowazekii but they differ from them by their high sensitivity to freezing and refreezing and by poor multiplication in yolk sacs of chick embryos. There is at present no evidence that these organisms cause human illness and no ecological information is available. We suggest they may be some new species of rickettsiae or rickettsia-like organisms.