Tick-borne rickettsial diseases: emerging risks in Europe.

Ticks are currently considered the main vectors of human infectious diseases in Europe, particularly since their role in the transmission of the agent of Lyme borreliosis was demonstrated in the 1980s. In the recent years, ticks have also been shown to be the vectors of numerous emerging rickettsial diseases. Although Mediterranean spotted fever (MSF) due to Rickettsia conorii was thought for a long time to be the only tick-borne rickettsial disease prevalent in Europe, five more spotted fever rickettsiae have been described as emerging pathogens in the last decade. Further, cases of infection due to Anaplasma phagocytophilum, the agent of human anaplasmosis (previously known as human granulocytic ehrlichiosis), have been reported throughout Europe. We present here these emerging diseases and discuss other potential threat for the future.