Blood smear examination matters: an incidental case of tick-borne relapsing fever in a traveller returning from Senegal

Relapsing fever is caused by various species of Borrelia bacteria and is traditionally categorized into louse-borne relapsing fever (LBRF) and tick-borne relapsing fever (TBRF). The epidemiological patterns differ according to the vector: LBRF is typically linked to epidemic outbreaks, while TBRF usually presents with an endemic distribution. Even though TBRF is endemic also in the Mediterranean Basin, diagnosis is mainly incidental in migrants or visiting friends and relatives travelling from sub-Saharan Africa. We report a case of TBRF with aseptic meningitis caused by Borrelia crocidurae/duttonii/hispanica in a 46-year-old Senegalese man, diagnosed through blood smear examination performed during the diagnostic workup for malaria. Diagnosis of TBRF is still primarily based on the direct detection of spirochetes in blood smear, although novel molecular methods (PCR) have recently been developed. Awareness, especially in non-endemic areas, and a One Health approach are crucial. Such an approach should aim to monitor the spread of Borrelia species, their vectors, and animal reservoirs, as well as to study their interactions with the environment and climate.