Rickettsioses. Rickettsioses are caused by intracellular bacteria from order of rickettsiales. They are transmitted by arthropods, mainly ticks, lice, fleas or other species close to chiggers, mainly in tropical areas. Some rickettsioses are endemic in France and others can be seen in patients returning from travel, including those presenting with "fever of unknown origin". Rickettsiae can't be isolated by conventional blood cultures in the laboratory. The diagnosis of rickettsial diseases is often made by serology, but specific PCR based on the swab of an inoculation eschar when it is present is a simple and rapid tool. The standard treatment for rickettsioses is doxycycline, that should be started as soon as clinical suspicion occurs, before diagnostic confirmation since some rickettsial diseases can be fatal.