Tick-borne rickettsioses in Europe

Rickettsioses are caused by obligate intracellular bacteria within the genus Rickettsia, mainly transmitted by arthropods. Until recently, Mediterranean spotted fever (MSF) caused by Rickettsia conorii was considered the only tick-borne rickettsiosis in Europe. However, 'new' TBR have been described in Europe during last years. For instance, other subspecies such as R. conorii caspia and R. conorii israelensis have been involved in MSF. Dermacentor-borne necrosis erythema and lymphadenopathy/tick-borne lymphadenopathy (DEBONEL/TIBOLA) cases caused by Rickettsia slovaca, Rickettsia raoultii, and Rickettsia rioja been described in several countries where Dermacentor marginatus ticks (the mainly implicated vector) are present. Rickettsia helvetica has also been involved as a human pathogen in cases of fever with and without rash and in patients with meningitis and carditis. Other TBR such as lymphangitis-associated rickettsioses (LAR), caused by Rickettsia sibirica mongolitimonae, have been diagnosed in different European countries (France, Spain, Portugal and Greece). Rickettsia massiliae is considered an etiological agent of MSF-like illness in the Mediterranean basin. Furthermore, Rickettsia monacensis that is distributed all along Europe has been isolated from patients with MSF-like illness in Spain. Although Rickettsia aeschlimannii has been associated with MSF-like in Africa and is distributed in the Mediterranean area, no autochthonous human cases have been reported for Europe. Other Rickettsia species detected in ticks and unrelated to human disease (Candidatus Rickettsia kotlanii, Candidatus Rickettsia barbariae, Candidatus Rickettsia vini) could be potentially involved in the next years. Climate changes, among other factors, may contribute to the emergence of other rickettsioses or change their distribution. Lastly, African tick-bite fever (ATBF), caused by Rickettsia africae, is frequently diagnosed in Europe in patients returning from endemic areas.