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Risk Factors for African Tick-Bite Fever in Rural Central Africa

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  • Department of Biochemistry and Microbiology, University of Buea, Buea, Cameroon; Department of Epidemiology, and Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland; Global Viral Forecasting Initiative, San Francisco, California; Johns Hopkins Cameroon Program/CRESAR, BP 7039 Yaoundé, Cameroon; Department of Biochemistry and Microbiology, University of Fort Hare, Alice, South Africa; Department of Epidemiology, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania; Program in Human Biology, Stanford University, Stanford, California

African tick-bite fever is an emerging infectious disease caused by the spotted fever group Rickettsia, Rickettsia africae, and is transmitted by ticks of the genus Amblyomma. To determine the seroprevalence of exposure to R. africae and risk factors associated with infection, we conducted a cross-sectional study of persons in seven rural villages in distinct ecological habitats of Cameroon. We examined 903 plasma samples by using an indirect immunofluorescence assay for antibodies to R. africae and analyzed demographic and occupational data collected from questionnaires. Of the 903 persons tested, 243 (26.9%) had IgG/IgM/IgA reactive with R. africae. Persons from four of the seven village sites were significantly more likely to be seropositive (P < 0.05), and lowland forest sites tended to have higher seroprevalences. These results suggest that African tick-bite fever is common in adults in rural areas of Cameroon and that ecological factors may play a role in the acquisition of R. africae infection.

Author Notes

*Address correspondence to Nathan D. Wolfe, Global Viral Forecasting Initiative, San Francisco, CA 94104. E-mail: nwolfe@gvfi.org

Financial support: This study was supported by awards from the U.S. Military HIV Research Program, the National Institutes of Health Director's Pioneer Award (grant DP1-OD000370), the W.W. Smith Charitable Trust, and grants from the National Institutes of Health Fogarty International Center (International Research Scientist Development Award grant 5 K01 TW000003-05), AIDS International Training and Research Program (grant 2 D 43 TW000010-17-AITRP), Johns Hopkins Bloomberg School of Public Health, Center for AIDS Research (grant P30 AI42855), and the National Geographic Society Committee for Research and Exploration (grant #7762-04). The U.S. Embassy also provided support through the Humanitarian Assistance Program, as did google.org and the Skoll Foundation.

Authors' addresses: Lucy M. Ndip, Landry E. Nfonsam, and Marie A. Bissong, Department of Biochemistry and Microbiology, University of Buea, Buea, South West Province, Cameroon. Hope H. Biswas, Department of Epidemiology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD. Matthew LeBreton, Emmanuel Mpoudi-Ngole, Cyrille Djoko, and Ubald Tamoufe, Johns Hopkins Cameroon Program/CRESAR, Yaoundé, Cameroon. Roland N. Ndip, Department of Biochemistry and Microbiology, Faculty of Science and Agriculture, University of Fort Hare, Alice, Republic of South Africa. A. Tassy Prosser, Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD. Donald S. Burke, Department of Epidemiology, University of Pittsburgh Graduate School of Public Health, Pittsburgh, PA. Nathan D. Wolfe, Global Viral Forecasting Initiative, San Francisco, CA and Program in Human Biology, Stanford University, Stanford, CA, E-mail: nwolfe@gvfi.org.

Reprints requests: Nathan D. Wolfe, Global Viral Forecasting Initiative, San Francisco, CA and Program in Human Biology, Stanford University, Stanford, CA 94305.

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