Abstract

West African tick-borne relapsing fever is an endemic disease due to Borrelia crocidurae. The tick Alectorobius sonrai is the only known vector of this bacterium. Several species of rodents and insectivores may be reservoir for this spirochete. The geographic distribution of Borrelia crocidurae is not well known. The zone where the presence of the vector has been recorded is situated in Sahelian regions, from Mauritania and northern Senegal up to Chad. In Senegal, it has been shown that the persistence of drought is responsible for a considerable spread of tick-borne relapsing fever to the south. Few epidemiological data are available about West African tick-borne relapsing fever. In Senegal, epidemiological investigations indicate that Borrelia crocidurae is a major cause of morbidity (annual incidence rate of 5.1%). The relapsing nature of tick-borne borreliosis depends on Borrelia's antigenic variability. Except relapsing febrile episodes, this illness presents no pathognomonic signs. Borrelia crocidurae relapsing fever is generally benignant but neurologic or ocular complications can occur. The diagnosis of tick-borne relapsing fever is made by demonstrating the presence of Borrelia in peripheral blood in thick smear, by intraperitoneal inoculation of mice or more recently with quantitative buffy coat method (QBC test). The best treatment for relapsing fever is tetracycline or doxycycline. When tetracyclines are contraindicated, the alternative is erythromycin. In neurologic complications, the effective treatment is intravenous penicillin G or ceftriaxone. West African tick-borne relapsing fever must be systematically mentioned in case of fever in a patient returning from the endemic area.