The Attributable Fraction of the Lymphatic Filariasis Burden to Water Resource Development and Management

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) sub-regions 1 and 2 mosquito densities of the Anopheles gambiae complex and An. 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. INTRODUCTION People living in tropical and sub-tropical countries have long suffered under the yoke of lymphatic filariasis (LF). This chronic parasitic disease is of great public health and socio-economic significance and is currently endemic in 80 countries/territories of the world. LF accounts for serious disfiguration and incapacitation of the extremities and the genitals and causes hidden internal damage to lymphatic and renal systems. Disease, disability, and disfiguration are responsible for a loss of worker productivity, significant treatment costs and social stigma. At present, the global burden of LF is estimated at 5.78 million disability adjusted life years (DALYs) lost annually. Hence, its