title: Endemic foci of the tick-borne relapsing fever spirochete Borrelia crocidurae in Mali, West Africa, and the potential for human infection.
abstract: BACKGROUND
  Tick-borne relapsing fever spirochetes are maintained in endemic foci that involve a diversity of small mammals and argasid ticks in the genus Ornithodoros. Most epidemiological studies of tick-borne relapsing fever in West Africa caused by Borrelia crocidurae have been conducted in Senegal. The risk for humans to acquire relapsing fever in Mali is uncertain, as only a few human cases have been identified. Given the high incidence of malaria in Mali, and the potential to confuse the clinical diagnosis of these two diseases, we initiated studies to determine if there were endemic foci of relapsing fever spirochetes that could pose a risk for human infection.
  
  
  RESULTS
  We investigated 20 villages across southern Mali for the presence of relapsing fever spirochetes. Small mammals were captured, thin blood smears were examined microscopically for spirochetes, and serum samples were tested for antibodies to relapsing fever spirochetes. Ornithodoros sonrai ticks were collected and examined for spirochetal infection. In total, 11.0% of the 663 rodents and 14.3% of the 63 shrews tested were seropositive and 2.2% of the animals had active spirochete infections when captured. In the Bandiagara region, the prevalence of infection was higher with 35% of the animals seropositive and 10% infected. Here also Ornithodoros sonrai were abundant and 17.3% of 278 individual ticks tested were infected with Borrelia crocidurae. Fifteen isolates of B. crocidurae were established and characterized by multi-locus sequence typing.
  
  
  CONCLUSIONS
  The potential for human tick-borne relapsing fever exists in many areas of southern Mali.
authors.affiliation: Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, Hamilton, Montana, United States of America.
authors.forename: Tom G
authors.initials: TG
authors.lastname: Schwan
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Anderson
authors.forename: Job E
authors.initials: JE
authors.lastname: Lopez
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Fischer
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Raffel
authors.forename: Brandi N
authors.initials: BN
authors.lastname: McCoy
authors.forename: David
authors.initials: D
authors.lastname: Safronetz
authors.forename: Nafomon
authors.initials: N
authors.lastname: Sogoba
authors.forename: Ousmane
authors.initials: O
authors.lastname: Maïga
authors.forename: Sékou F
authors.initials: SF
authors.lastname: Traoré
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001769:Blood / Q000382:microbiology*; D001898:Borrelia / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D019353:Endemic Diseases; D006801:Humans; D008302:Mali / Q000453:epidemiology; D008853:Microscopy; D008969:Molecular Sequence Data; D026861:Ornithodoros; D015995:Prevalence; D012061:Relapsing Fever / Q000453:epidemiology / Q000662:veterinary*; D012377:Rodentia; D017422:Sequence Analysis, DNA; D012788:Shrews
chemical_list: D000907:Antibodies, Bacterial