title: Seroepidemiology of Rickettsia africae infection in Norwegian travellers to rural Africa.
abstract: Rickettsia africae is the causative agent of African tick bite fever (ATBF), an acute febrile illness frequently accompanied by inoculation eschars, regional lymphadenitis, myalgia and severe headache. Recently, ATBF has been recognized as an emerging health problem for international travellers to rural sub-Saharan Africa. To estimate the incidence, risk factors for and proportion of symptomatic cases of travel-associated R. africae infection, we performed a seroepidemiological study of 152 first-time Norwegian travellers to rural areas in sub-Equatorial Africa. Seropositivity was based on the detection of specific antibodies to R. africae in microimmunofluorescence and/or Western blotting assays. Thirteen (8.6%) travellers were seropositive to R. africae. Eight (62%) seropositive travellers reported symptoms consistent with ATBF; of these, 2 had received antirickettsial therapy. Using multiple logistic regression, the following factors were found to be significantly associated with seropositivity: hunting as the purpose of travel [odds ratio (OR) 10.1; 95% confidence interval (CI) 1.5-69; p=0.019] and stay in rural areas of > 7 d (OR 6.0; 95% CI 1.5-24; p=0.012). This first seroepidemiological study on travel-associated R. africae infection suggests that the infection may be common in international travellers to rural sub-Saharan Africa but that most cases are asymptomatic or clinically mild and self-limited.
authors.affiliation: Department of Internal Medicine, Aker University Hospital, Oslo, Norway.
authors.forename: Mogens
authors.initials: M
authors.lastname: Jensenius
authors.forename: Terje
authors.initials: T
authors.lastname: Hoel
authors.forename: Didier
authors.initials: D
authors.lastname: Raoult
authors.forename: Pierre-Edouard
authors.initials: PE
authors.lastname: Fournier
authors.forename: Helge
authors.initials: H
authors.lastname: Kjelshus
authors.forename: Anne-Lise
authors.initials: AL
authors.lastname: Bruu
authors.forename: Bjørn
authors.initials: B
authors.lastname: Myrvang
mesh_terms: D000293:Adolescent; D000328:Adult; D017954:Africa South of the Sahara; D015153:Blotting, Western; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D016017:Odds Ratio; D012281:Rickettsia / Q000276:immunology / Q000302:isolation & purification*; D012282:Rickettsia Infections / Q000175:diagnosis* / Q000453:epidemiology* / Q000209:etiology / Q000276:immunology; D012307:Risk Factors; D012424:Rural Population; D016036:Seroepidemiologic Studies; D017282:Tick-Borne Diseases / Q000175:diagnosis* / Q000453:epidemiology* / Q000209:etiology / Q000276:immunology; D014195:Travel