Abstract
BackgroundIn West Africa, tick-borne relapsing fever is a neglected arthropod-borne infection caused by Borrelia crocidurae transmitted by the argasid tick Ornithodoros sonrai. From an epidemiological point of view, it is of interest to know whether some genotypes of the vector are specialized in carrying certain genotypes of the pathogen.FindingsThirty-five O. sonrai ticks collected in Mali, Senegal, Mauritania and Morocco confirmed to be B. crocidurae-infected, were genotyped by 16S rRNA gene sequencing. B. crocidurae was genotyped by Multispacer Sequence Typing. The 35 O. sonrai ticks grouped into 12 genotypes with strong geographical structuration. MST resolved the 35 B. crocidurae isolates into 29 genotypes with pairwise divergence of 0.09 - 1.56 % without strict geographical structuration as genotype ST22 was found in Mali, Senegal and Mauritania. There was no evidence of tick-borrelia specialization as one O. sonrai genotype carried several B. crocidurae genotypes and one B. crocidurae genotype was found in different O. sonrai genotypes.ConclusionsThis report illustrates a non-specialized circulation of B. crocidurae borreliae within O. sonrai ticks in West Africa.
Highlights
In West Africa, tick-borne relapsing fever is a neglected arthropod-borne infection caused by Borrelia crocidurae transmitted by the argasid tick Ornithodoros sonrai
The B. crocidurae-infected ticks here investigated comprised one tick from Morocco (1 site), three ticks from Mauritania (1 site), twenty-seven ticks from Senegal (8 sites) and four ticks from Mali (4 sites) (Table 1)
As for tick genotyping, all positions containing gaps and missing data were eliminated from the 441-bp aligned fragment of 16S rRNA gene sequences of O. sonrai
Summary
In West Africa, tick-borne relapsing fever is a neglected arthropod-borne infection caused by Borrelia crocidurae transmitted by the argasid tick Ornithodoros sonrai. Borrelia crocidurae is one of the spirochetes responsible for tick-borne relapsing fever in North and West Africa [1]. In these countries, borreliae are maintained between Ornithodoros sonrai argasid ticks and rodents while the humans get infected accidently [2, 3]. B. crocidurae has been detected in O. sonrai ticks collected in Tunisia, Morocco, Mauritania, Senegal [4] and Mali [3]. In Morocco, borreliae infection was found in 10.2 % of ticks and 8.6 % of tested rodents and insectivores [5]. An average incidence of 11 per 100 person-years was reported in humans at Senegal [2]
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