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Lymphatic filariasis (LF) is a debilitating disease overwhelmingly caused by Wuchereria bancrofti, which is transmitted by various mosquito species. Here, we present a systematic literature review with the following objectives: (i) to establish global and regional estimates of populations at risk of LF with particular consideration of water resource development projects, and (ii) to assess the effects of water resource development and management on the frequency and transmission dynamics of the disease. We estimate that globally, 2 billion people are at risk of LF. Among them, there are 394.5 million urban dwellers without access to improved sanitation and 213 million rural dwellers living in close proximity to irrigation. Environmental changes due to water resource development and management consistently led to a shift in vector species composition and generally to a strong proliferation of vector populations. For example, in World Health Organization (WHO) subregions 1 and 2, mosquito densities of the Anopheles gambiae complex and Anopheles funestus were up to 25-fold higher in irrigated areas when compared with irrigation-free sites. Although the infection prevalence of LF often increased after the implementation of a water project, there was no clear association with clinical symptoms. Concluding, there is a need to assess and quantify changes of LF transmission parameters and clinical manifestations over the entire course of water resource developments. Where resources allow, integrated vector management should complement mass drug administration, and broad-based monitoring and surveillance of the disease should become an integral part of large-scale waste management and sanitation programs, whose basic rationale lies in a systemic approach to city, district, and regional level health services and disease prevention.
Received September 19, 2004. Accepted for publication January 22, 2005.
Acknowledgments: The authors thank Dr. Felix P. Amerashinge, Prof. David H. Molyneux, Dr. Will Parks, Dr. Erling Pedersen, and Dr. Christopher A. Scott for valuable comments on the manuscript. We also thank Jacqueline V. Druery and her team from Stokes Library at Princeton University for help in obtaining a large body of relevant literature.
Financial support: This investigation received financial support from the Water, Sanitation and Health unit and the Protection of the Human Environment (WSH/PHE) at the World Health Organization (WHO ref. Reg. file: E5/445/15). The research of J. Keiser and J. Utzinger is supported by the Swiss National Science Foundation (Projects PMPDB–106221 and PPOOB–102883, respectively). M. C. Castro is grateful to the Office of Population Research and the Centre for Health and Wellbeing at Princeton University.
* Address correspondence to Jürg Utzinger, Department of Public Health and Epidemiology, Swiss Tropical Institute, CH-4002 Basel, Switzerland. E-mail: juerg.utzinger{at}unibas.ch
Authors’ addresses: Tobias E. Erlanger, Jennifer Keiser, Marcel Tanner, and Jürg Utzinger, Swiss Tropical Institute, P.O. Box, CH–4002 Basel, Switzerland. Marcia Caldas de Castro, Department of Geography, University of South Carolina, 125 Callcott Hall, Columbia, SC 29208. Robert Bos, Department of Protection of the Human Environment, World Health Organization; 20 Avenue Appia, CH–1211 Geneva 27, Switzerland. Burton H. Singer, Office of Population Research, Princeton University, 245 Wallace Hall, Princeton, NJ 08544.
Reprint requests: Jürg Utzinger, Department of Public Health and Epidemiology, Swiss Tropical Institute, CH–4002 Basel, Switzerland, Telephone: +41 61 284-8129, Fax: +41 61 284-8105, E-mail: juerg.utzinger{at}unibas.ch.
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