So far there haven’t been any efficient methods for treating chronic Q fever and chronic fatique syndrome caused by the bacterium Coxiella burnetii. In order to develop new therapeutic strategies it is essential to improve our knowledge about C. burnetii pathogenesis and ways of infection. The role of ticks as vectors and reservoir for Q-fever is still unclear. Therefore the transmission by ticks as vectors should be clarified in more detail.To evaluate the transmission of Coxiella, an in vitro feeding system for ticks based on previously published protocols will be developed. The transmission of pathogens (C. burnetii) into the tick as well as their proliferation, distribution and excretion will be investigated by molecular biological and cell biological methods. The results acquired in this project are supposed to clarify the role of ticks in Q fever and to lead to a better understanding of this infection and its transmission.