The detection of rickettsia-like microorganisms within the ovaries of female Ixodes ricinus ticks.

An ultrastructural study of tick-borne fever (TBF)-infected Ixodes ricinus ticks revealed the presence of rickettsia-like microorganisms within the ooplasm and the mitochondria of developing oocytes. These microorganisms are similar in appearance to the TBF agent and it is possible that although transovarial transmission of the TBF agent apparently does not occur, the rickettsiae are at least able to establish themselves in the ovaries of infected ticks.