Impact on health caused by water resources development and management projects and health impact assessment as a tool for mitigation

Since the rise of early civilisations people have adapted and modified water bodies for their use.
Water is made available through dams, wells, canals and other infrastructure to provide drinking
water for households and livestock and to feed irrigated agriculture. Despite myriad benefits due
to water resources development and management there are also adverse effects. Certain
components of it can facilitate the transmission of infectious diseases or impact the psychosocial
conditions of affected communities and individuals.
The framework of this PhD thesis is built around ascertaining the nature and scale of
health impacts caused by water resources development and management projects in order to
facilitate the prevention and mitigation of these impacts. Part I deals with dams and with health
issues in connection with the construction of the Nam Theun 2 hydroelectric project (NT2) in
the Lao People’s Democratic Republic. Part II discusses the role of health impact assessment
(HIA) as a tool for the systematic appraisal of positive and negative health effects of projects,
programmes and policies. Part III focuses on the impact of water resources development and
management projects on the transmission of lymphatic filariasis and Japanese encephalitis. In
Part IV the effectiveness of different methods for dengue vector control is analysed.
Part I: Dams can positively or negatively impact various aspects of health. Dam projects can
generate revenue for development and increase the output of agricultural production by feeding
irrigation systems. Negative impacts from constructions may include the proliferation of vectors
that transmit infectious diseases, mental health problems in resettled communities or increased
rates of sexually-transmitted infections around work camps.
The analysis of baseline health data of the people in the two areas (the Nakai plateau
where the dam will be located and Xe Bang Fai downstream area where the water will be
discharged) that are in proximity to the NT2 project revealed that malnutrition is a considerable
public health issue. 56% of the children younger than 5 years in Nakai and 36% of the children
in Xe Bang Fai were estimated to be underweight. Infection with intestinal nematodes was
another significant public health problem. An infection with Ascaris lumbricoides was found in
68% and hookworms in 9.7% of the population surveyed on the Nakai plateau. Malaria was of
less importance and due to expected reduction of the vector’s habitat (deforestation), malaria
prevalence may further decrease in the future. The NT2 project also has large potential to
improve health. Increased incomes through construction and development could improve the
nutritional situation and the construction of water and sanitation systems in the resettlement
villages may lead to an overall decrease in the prevalence of infectious diseases.
Analysis of existing data on health seeking behaviour showed substantial differences between
the highland Nakai community and the lowland Xe Bang Fai communities. Self-treatment with
anti-malarial drugs (chloroquine and sulfadoxine-pyrimethamine) was practiced by 32% and 7%
of the people with malaria symptoms in Xe Bang Fai in Nakai, respectively. The mean amount
spent per person for one consultation was US$ 1.7 in Nakai and US$ 7.2 in Xe Bang Fai.
Part II: Health impact assessment of projects, programmes and policies is a methodology that
aims at identifying and mitigating negative health effects and enhancing positive ones. Over the
past two decades, HIA has been developed, and has become an integral part of public-health
policies in industrialised countries. However, in the developing world, the institutionalisation of
HIA still has some distance to go. We assessed and quantified the number of HIA related
publications in the peer-reviewed literature and discussed the need for conducting HIA in the
developing world, which can be clearly seen in petroleum and water resources development
projects. A systematic literature search revealed that less than 6% of the publications had a
specific focus on developing countries. Hence, there is a pressing need for HIA in the
developing world, particularly in view of current predictions of major petroleum and water
resources development projects, and China’s increasing investment in the oil and water sectors
across Africa. Vector-borne and water-based diseases, for example, are key public-health issues
in tropical and sub-tropical environments. Major infrastructural projects can induce
environmental change which in turn might spur transmission of those diseases. Since the
Chinese government and Chinese enterprises currently lack experience in conducting HIA, we
argue that these projects are unlikely to be built and operated in an environmentally and public
health friendly manner. We suggest that binding international regulations should be created to
insure that projects, programmes and policies undergo HIA, particularly if they are constructed
in the developing world.
Part III: In this study we investigated the impact of irrigation on the transmission of Japanese
encephalitis. Currently, there are approximately 220 million people living in proximity to
irrigated agriculture. Over the past 40 years, the land area irrigated for rice cultivation increased
by 22% in Japanese encephalitis-endemic countries. This may contribute to the steadily
increasing incidence of Japanese encephalitis in those countries. We show that intermittent
irrigation could interrupt the life cycle of the vector Culex tritaeniorhynchus, which could lead
to an elimination of up to 91% of the immature stages of the vector.
In a second study, we calculated that worldwide over 2 billion people are at risk of
lymphatic filariasis. Of those, 213 million live in proximity to irrigated agriculture and 394.5
million live in urban areas with inadequate sanitation facilities. In Bangladesh, India, Myanmar
and Nepal alone, we find 52% of the burden, 29% of the people at risk, 69% of the size of the
population at risk due to proximity to irrigated land and 33% of the population that lacks of
improved sanitation. Water resources development and management can lead to a proliferation
of the following vectors: Anopheles gambiae, An. funestus, An. barbirostris, Cx.
quinquefasciatus, Cx. pipiens pipiens, Cx. antennatus and Aedes polynesiensis. However, it can
also curb the breeding of An. pharoensis, An. melas, An. subpictus und Ae. samoanus. We argue
that there is a considerable need to investigate the impact of water resources development and
management on clinical parameters of lymphatic filariasis.
Part IV: Dengue, which is transmitted by Ae. aegypti and Ae. albopictus, is the most prevalent
arboviral disease. The global incidence of dengue is 50-100 million cases annually, with up to
500,000 resulting in hemorrhagic fever or dengue shock syndrome. The vectors show breeding
preferences for domestic water containers. Vector control remains the cornerstone for the
prevention and control of dengue, however, there is a paucity of evidence regarding the
effectiveness and applicability of different vector control methods. We conducted a systematic
literature search and identified 56 publications. From these, we could extract relevant data about
61 dengue vector control interventions, trials and programmes. By means of a meta-analysis we
compared the effectiveness of chemical control, biological control, environmental management
and integrated vector management (several methods combined).
We found that integrated vector management is the most effective method to reduce the
Breteau index (number of containers per 100 houses infected with dengue vectors), the house
index (percent of houses with infected containers) and the container index (percent of containers
infected), resulting in random combined relative effectiveness of 0.33, 0.17, and 0.12,
respectively (0 means complete elimination of breeding comtainers, whereas 1 reflects no
change). Environmental control showed a relatively low effectiveness, i.e. 0.71 for the Breteau
index, 0.43 for the house index and 0.49 for the container index. Biological control usually
targeted a small number of people (median population size: 200; range: 20-2500), whereas
integrated vector management focused on larger populations (median: 12,450; range: 210-
9,600,000).