The Epidemiology and Geographic Distribution of Relapsing Fever Borreliosis in West and North Africa, with a Review of the Ornithodoros erraticus Complex (Acari: Ixodida)

Abstract

BackgroundRelapsing fever is the most frequent bacterial disease in Africa. Four main vector / pathogen complexes are classically recognized, with the louse Pediculus humanus acting as vector for B. recurrentis and the soft ticks Ornithodoros sonrai, O. erraticus and O. moubata acting as vectors for Borrelia crocidurae, B. hispanica and B. duttonii, respectively. Our aim was to investigate the epidemiology of the disease in West, North and Central Africa.Methods And FindingsFrom 2002 to 2012, we conducted field surveys in 17 African countries and in Spain. We investigated the occurrence of Ornithodoros ticks in rodent burrows in 282 study sites. We collected 1,629 small mammals that may act as reservoir for Borrelia infections. Using molecular methods we studied genetic diversity among Ornithodoros ticks and Borrelia infections in ticks and small mammals. Of 9,870 burrows investigated, 1,196 (12.1%) were inhabited by Ornithodoros ticks. In West Africa, the southern and eastern limits of the vectors and Borrelia infections in ticks and small mammals were 13°N and 01°E, respectively. Molecular studies revealed the occurrence of nine different Ornithodoros species, including five species new for science, with six of them harboring Borrelia infections. Only B. crocidurae was found in West Africa and three Borrelia species were identified in North Africa: B. crocidurae, B. hispanica, and B. merionesi.Conclusions Borrelia Spirochetes responsible for relapsing fever in humans are highly prevalent both in Ornithodoros ticks and small mammals in North and West Africa but Ornithodoros ticks seem absent south of 13°N and small mammals are not infected in these regions. The number of Ornithodoros species acting as vector of relapsing fever is much higher than previously known.

Monoclonal Antibodies for the Diagnosis of Borrelia crocidurae

“…The most recent epidemiological data indicate that 43.92 million people living in rural Africa in endemic countries and 19.17 million travelers are at risk of relapsing fever in West and North African countries. 32 Extrapolating on the 11% incidence of tick-borne relapsing fever measured in rural Senegal, 33 this represents about 4.82 million cases of relapsing fever a year. Indeed, both antibodies could be incorporated into a format well suited for the rapid point-of-care diagnosis of relapsing fever in both endemic countries 3 and in countries with travelers.…”

Ubiquitous bacteria Borrelia crocidurae in Western African ticks Ornithodoros sonrai

“…This observation however, was made before tools were available for a fine discrimination between both ticks and borreliae groups. Recently, such sequencing-based tools allowed refining the diversity of O. sonrai ticks into nine subgroups [7]. Likewise, MLST [3] and multiple spacer sequence typing (MST) [8] discriminated groups among B. crocidurae .…”

“…Likewise, MLST [3] and multiple spacer sequence typing (MST) [8] discriminated groups among B. crocidurae . Genotyping found a strong geographical structuration of the O. sonrai tick population [7], however, it remains unknown whether certain O. sonrai genetic variants are specialized in certain genetic variants of B. crocidurae . The aim of the present work was to investigate this question using modern molecular tools for genotyping O. sonrai ticks infected by B. crocidurae .…”

Blood-Borne Candidatus Borrelia algerica in a Patient with Prolonged Fever in Oran, Algeria

“…2 Borrelia crocidurae has been detected with a 2.5% prevalence in Ornithodoros sonrai ticks, 3 while Lyme group Borrelia garinii was recently detected in Ixodes ricinus ticks, collected from El Ghora, Algeria. 4 In addition, at least 10 different relapsing fever-causing borreliae have been documented in Africa, including five different borreliae in humans and five different borreliae in nonhuman hosts.…”