Laboratory Diagnosis of Tick-Borne African Relapsing Fevers: Latest Developments.

Aurélien Fotso Fotso,Michel Drancourt

doi:10.3389/fpubh.2015.00254

Abstract

In Africa, relapsing fevers caused by ectoparasite-borne Borrelia species are transmitted by ticks, with the exception of Borrelia recurrentis, which is a louse-borne spirochete. These tropical diseases are responsible for mild to deadly spirochetemia. Cultured Borrelia crocidurae, Borrelia duttonii, and Borrelia hispanica circulate alongside at least six species that have not yet been cultured in vectors. Direct diagnosis is hindered by the use of non-specific laboratory tools. Indeed, microscopic observation of Borrelia spirochaeta in smears of peripheral blood taken from febrile patients lacks sensitivity and specificity. Although best visualized using dark-field microscopy, the organisms can also be detected using Wright–Giemsa or acridine orange stains. PCR-based detection of specific sequences in total DNA extracted from a specimen can be used to discriminate different relapsing fever Borreliae. In our laboratory, we developed a multiplex real-time PCR assay for the specific detection of B. duttonii/recurrentis and B. crocidurae: multispacer sequence typing accurately identified cultured relapsing fever borreliae and revealed diversity among them. Other molecular typing techniques, such as multilocus sequence analysis of tick-borne relapsing fever borreliae, showed the potential risk of human infection in Africa. Recent efforts to culture and sequence relapsing fever borreliae have provided new information for reassessment of the diversity of these bacteria. Recently, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry has been reported as a means of identifying cultured borreliae and of identifying both vectors and vectorized pathogens such as detecting relapsing fever borreliae directly in ticks. The lack of a rapid diagnosis test restricts the management of such diseases. We produced monoclonal antibodies against B. crocidurae in order to develop cheap assays for the rapid detection of relapsing fever borreliae. In this paper, we review point-of-care diagnosis and confirmatory methods.

Highlights

In Africa, relapsing fever borreliae are neglected vector-borne pathogens responsible for various febrile presentations and are most commonly suspected in malaria-like symptoms [1]
Three cultured tick-borne species (Borrelia crocidurae, Borrelia duttonii, and Borrelia hispanica) [2] are in circulation, in addition to the as yet uncultured Borrelia merionesi in Ornithodoros ticks in Morocco [3], Candidatus Borrelia algerica in febrile patients in Algeria [4] and an unnamed new species in Ornithodoros porcinus ticks in Tanzania [5], in the blood of Spheniscus demersus penguins in South Africa [6], in Rhipicephalus evertsi ticks from Nigeria [7], and new Borrelia species distinct from the Lyme disease and recurrent fever groups detected in Amblyomma cohaerens in Ethiopia [8]
Since relapsing fever borreliae can present with fever, they are often misdiagnosed as malaria [11]

Summary

INTRODUCTION

In Africa, relapsing fever borreliae are neglected vector-borne pathogens responsible for various febrile presentations and are most commonly suspected in malaria-like symptoms [1] They are ectoparasite-borne infections that are transmitted by ticks, with the exception of Borrelia recurrentis, which is a louse-borne spirochete [1]. Because of the close genetic and genomic proximity of the relapsing fever borreliae, as illustrated by 16S rRNA gene sequence variability ≤1%, confirmed by B. duttonii and B. recurrentis genomics, indicating that the two organisms belonged to the same bacterial species [22,23,24], molecular tests may detect. MST looks for differences between five IGSs in B. crocidurae, B. duttonii, and B. recurrentis genomes It is a suitable PCR-sequencing-based method for identifying and genotyping relapsing fever borreliae in Africa in both vectors and clinical specimens [13]. B. hispanica is responsible for relapsing fever borreliae in Spain [31] and previous molecular

Methods

Findings

CONCLUSION