Significance of Travel to Rural Areas as a Risk Factor for Malarial Anemia in an Urban Setting

Jose G. Siri Department of Epidemiology, and Department of Bioststistics, School of Public Health, University of Michigan, Ann Arbor, Michigan; Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; Centre for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya

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Mark L. Wilson Department of Epidemiology, and Department of Bioststistics, School of Public Health, University of Michigan, Ann Arbor, Michigan; Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; Centre for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya

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Susan Murray Department of Epidemiology, and Department of Bioststistics, School of Public Health, University of Michigan, Ann Arbor, Michigan; Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; Centre for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya

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Daniel H. Rosen Department of Epidemiology, and Department of Bioststistics, School of Public Health, University of Michigan, Ann Arbor, Michigan; Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; Centre for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya

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John M. Vulule Department of Epidemiology, and Department of Bioststistics, School of Public Health, University of Michigan, Ann Arbor, Michigan; Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; Centre for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya

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Laurence Slutsker Department of Epidemiology, and Department of Bioststistics, School of Public Health, University of Michigan, Ann Arbor, Michigan; Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; Centre for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya

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Kim A. Lindblade Department of Epidemiology, and Department of Bioststistics, School of Public Health, University of Michigan, Ann Arbor, Michigan; Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; Centre for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya

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The epidemiology of malaria in urban environments is poorly characterized, yet increasingly problematic. We conducted an unmatched case–control study of risk factors for malarial anemia with high parasitemia in urban Kisumu, Kenya, from June 2002 through February 2003. Cases (n = 80) were hospital patients with a hemoglobin level ≤ 8 g/dL and a Plasmodium parasite density ≥ 10,000/μL. Controls (n = 826) were healthy respondents to a concurrent citywide knowledge, attitude, and practice survey. Children who reported spending at least one night per month in a rural area were especially at risk (35% of cases; odds ratio = 9.3, 95% confidence interval [CI] = 4.4–19.7, P < 0.0001), and use of mosquito coils, bed net ownership, and house construction were non-significant, potentially indicating that malaria exposure during rural travel comprises an important element of risk. Control of severe malaria in an urban setting may be complicated by Plasmodium infections acquired elsewhere. Epidemiologic studies of urban malaria in low transmission settings should take travel history into account.

Author Notes

*Address correspondence to Mark L. Wilson, Department of Epidemiology, School of Public Health, University of Michigan, 109 Observatory, Ann Arbor, MI 48109-2029. E-mail: wilsonml@umich.edu

Financial support: This research was supported by CDC/KEMRI and by the University of Michigan through the Rackham Graduate School, the Center for Research on Ethnicity, Culture and Health, and the Global Health Program.

Disclaimer: This manuscript was published with the approval of the Director of the Kenya Medical Research Institute. The findings and conclusions in this report are those of the author(s) and do not necessarily represent the views of the Centers for Disease Control and Prevention.

Authors' addresses: Jose G. Siri, Health and Global Change Project, International Institute for Systems Analysis, Laxenburg, Austria. Mark L. Wilson, Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, MI. Susan Murray, Department of Biostatistics, School of Public Health, University of Michigan, Ann Arbor, MI. Daniel H. Rosen and Laurence Slutsker, Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, GA. John M. Vulule, Centre for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya. Kim A. Lindblade, Centers for Diseases Control and Prevention Regional Office for Central America and Panama, Unit 3190, DPO AA.

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