Tick-borne relapsing fever Borreliosis, a major public health problem overlooked in Senegal (Publication with Expression of Concern)

Background Tick-borne relapsing fever (TBRF) is the most common vector-borne bacterial disease in humans in West Africa. It is frequently clinically confused with malaria. Our study aims to determine, on a micro-geographic scale, the conditions for the maintenance and spread of TBRF in the Niakhar district of Senegal. Methodology/Principal findings We conducted clinical, entomological and animal reservoir investigations. Field surveys were carried out in order to investigate the presence of Ornithodoros sonrai vector ticks and to detect Borrelia spp. by qPCR using the 16S rRNA and glpQ genes, respectively. Micromammal trapping series were carried out inside homes and Borrelia infection was detected using brain tissue qPCR. Capillary blood samples from febrile patients were also tested for Borrelia using qPCR. More than 97% (40/41) of the villages surveyed were infested with O. sonrai ticks. The prevalence of Borrelia spp. infections in ticks was 13% (116/910), and over 73% (85/116) were positively confirmed as being Borrelia crocidurae. Borreliosis cases accounted for 12% (94/800) of episodes of fever and all age groups were infected, with children and young people between the ages of 8-14 and 22-28 being the most infected by the disease (16% and 18.4%). TBRF cases occurred in all seasons, with a peak in August. In two species of small rodents that were found to be infected (Arvicanthis niloticus, Mus musculus), the proportion of Borrelia infection was 17.5% (10/57), and the highest prevalence of infection (40.9%, 9/22) was observed in A. niloticus. Conclusion/Significance Our study indicates that TBRF is an endemic disease in the Niakhar district, where children and young people are the most infected. Arvicanthis niloticus and O. sonrai ticks are massively present and appear to be the main epidemiological reservoirs causing its extensive spread to humans. Author summary Tick-borne relapsing fever (TBRF), remains an overlooked and neglected disease in the management of febrile patients in Senegal. The results of this study showed a high prevalence of rodent burrows infested with O. sonrai ticks (the vectors of the disease) inside human dwellings, with a common Borrelia infection affecting populations within the community in the Niakhar district of the Fatick region of Senegal. Borrelia infection was detected in several rodents belonging to two species of small mammals. In febrile patients studied in the area, all age groups were infected. TBRF cases were observed in all seasons. In the similar context to that of malaria pre-elimination observed in Dielmo and Ndiop villages, TBRF appears to be the predominant cause of morbidity among febrile patients. By extension, we believe this may be the same in many other endemic regions of the country which have not yet been clinically investigated. TBRF cases are probably undiagnosed in those endemic areas and are likely to be poorly managed in health posts and health centres.