Serological Evidence of Rickettsia Exposure among Patients with Unknown Fever Origin in Angola, 2016-2017.

P F Barradas,A C Teodoro,Z Neto,I Amorim,L Duarte,P Ferreira,R Sousa,H Gonçalves,F Gärtner,T L Mateus

doi:10.1155/2020/4905783

Abstract

Spotted fever group Rickettsia (SFGR) is one among the aetiologies that cause fever of unknown origin in Angola. Despite their occurrence, there is little information about its magnitude in this country either because it is misdiagnosed or due to the lack of diagnostic resources. For this purpose, eighty-seven selected malaria- and yellow fever-negative serum specimens collected between February 2016 and March 2017 as part of the National Laboratory of Febrile Syndromes, from patients with fever (≥37.5°C) for at least 4 days and of unknown origin, were screened for Rickettsia antibodies through an immunofluorescence assay (IFA). Serological results were interpreted according to the 2017 guidelines for the detection of Rickettsia spp. Three seroreactive patients had detectable IgM antibodies to Rickettsia with an endpoint titre of 32 and IgG antibodies with endpoint titres of 128 and 256. These findings supported a diagnosis of Rickettsia exposure amongst these patients and highlight that rickettsioses may be among the cause of unknown febrile syndromes in Angola. Therefore, physicians must be aware of this reality and must include this vector-borne disease as part of aetiologies that should be considered and systematically tested in order to delineate appropriate strategies of diagnostic and control of Rickettsia in Angola.

Highlights

Rickettsioses are vector-borne diseases of medical importance, in African countries where an increasing number of cases have been reported amongst residents and tourists [1]
Ese bacteria present several antigenically distinct groups, with those belonging to the spotted fever group (SFG) remaining an important cause of human and animal diseases, characterized by vascular invasion and tissue necrosis [5]. e classical triad of clinical manifestations of SFG Rickettsia infection includes fever, eschar, and rash [6]; these vary depending on the rickettsial species involved
Many studies report rickettsioses acquired by travellers, but the majority refers to sub-Saharan Africa tourists who develop African tick-bite fever (ATBF) [1]

Summary

Introduction

Rickettsioses are vector-borne diseases of medical importance, in African countries where an increasing number of cases have been reported amongst residents and tourists [1]. Ese bacteria present several antigenically distinct groups, with those belonging to the spotted fever group (SFG) remaining an important cause of human and animal diseases, characterized by vascular invasion and tissue necrosis [5]. In African countries, fevers of unknown origin can have different aetiologies including rickettsial infection but, due to the overlapping symptomatology with other endemic diseases (e.g., malaria, dengue, HIV, and brucellosis) that cause fever, as well as the lack of available diagnostic tests and laboratory resources [7], rickettsioses are often underdiagnosed [2]

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