AGRICULTURE AND HUMAN HEALTH Water- associated vector-borne diseases
OVERVIEW Water-associated vector-borne diseases • Nature • Magnitude Agricultural driving forces • Environmental • Social • Health status and agricultural production Activities in UN context and beyond • Historical review • Current activities • Issues and conclusions
What are vector-borne diseases ? • Malaria • Schistosomiasis • Lymphatic filariasis • Japanese encephalitis
What are vector-borne diseases ? • Malaria over 2 billion people at risk • Schistosomiasis 779 million people at risk • Lymphatic filariasis over 1 billion people at risk • Japanese encephalitis 1.9 billion people at risk
What are vector-borne diseases ? • Malaria 300-500 episodes every year • Schistosomiasis 207 million people infected • Lymphatic filariasis 120 million people infect • Japanese encephalitis 50,000 clinical cases reported every year
What are vector-borne diseases ? • Malaria > 1 million deaths a year • Schistosomiasis annually 15,000-100,000 deaths • Lymphatic filariasis no immediate deaths • Japanese encephalitis 15,000 deaths in 2001, fluctuates from year to year
What are vector-borne diseases ? In 2002: • Malaria 46.4 million DALYs lost • Schistosomiasis 1.7 million DALYs lost • Lymphatic filariasis 5.8 million DALYs lost • Japanese encephalitis 709,000 DALYs lost World Health Report 2004
What are vector-borne diseases ? Other relevant vector-borne diseases include • African trypanosomiasis – sleeping sickness, tsetseflies • Chagas disease (American trypanosomiasis) – triatomine bugs • Onchocerciasis – river blindness, blackflies • Leishmaniasis – visceral/cutaneous – sandflies • Plague, scrub typhus, (dengue), tick-borne encephalitis, (yellow fever)
What is the fraction of the burden attributable to irrigation ?
What is the fraction of the burden attributable to irrigation ? In 2002: • Malaria 46.4 million DALYs lost • Schistosomiasis 1.7 million DALYs lost • Lymphatic filariasis 5.8 million DALYs lost • Japanese encephalitis 709,000 DALYs lost 2003: work initiated with the Swiss Tropical Institute in Basel to carry out systematic and comprehensive literature reviews of the nature and magnitude of the links to water of four vector-borne diseases. The method combines the development of a causal web linking exposures and outcomes combined with Comparative Risk Assessment (CRA). A strengthened and expanded evidence base will help clarify the health impacts (in terms of Burden of Disease BOD and expressed in Disability Adjusted Life Years DALYs) of water resources that have been developed and are managed without due consideration of adverse health effects and health opportunities.
What is the fraction of the burden attributable to irrigation ? In 2002: • Malaria 46.4 million DALYs lost • Schistosomiasis 1.7 million DALYs lost • Lymphatic filariasis 5.8 million DALYs lost • Japanese encephalitis 709,000 DALYs lost It will also provide a solid foundation for the assessment of the cost-effectiveness of water-driven health interventions, including alternative design and construction options for water resources development projects, and improved water management practices. This will allow a comparison not only between different options for “water interventions”, but also between this type of interventions and other medical and public health interventions. It will help elucidate trade-offs, synergies and antagonisms whenever combinations of interventions are considered. It will also highlight situations where options with only a marginal benefit to the production output of other sectors become highly desirable because of their added health benefits. An example of this would be the case where investment in irrigation infrastructure results in marginal benefits for agricultural production, but has a substantial impact on the transmission reduction of malaria.
Water resource development and management Large dams, artificial lakesHydropower Large dams, river modificationsFlood control Small dams, irrigation schemes Agriculture Small dams, pondsAquaculture Pumps, drains Water supply & sanitation Pools, artificial lakesRecreation New breeding sites (e.g. reservoir, surface irrigation) Chang in atmospheric system (e.g. humidity) Change in ecosystemChange in hydrological system (e.g. water flow, chemistry) Creation and influence of larval/adult mosquito habitats Host 1: Domestic animals Plasmodium development, Plasmodium/Anopheles survival rate, Anopheles longevity,increase in Anopheles density Improve household living conditions, community resources, local economy, health infrastructure Vector control Water management Personal protection,chemoprophylaxis, vaccination Customs, culture Host 2:Local population, labour, migrants Susceptibility, immunity Legend: Anaemia, undernutrition, low birth weight, increased susceptibility to general infection Positive impact Clinical disease Infected human population Sequelae Negative impact Severe clinical complication Death Causal web
What is the fraction of the burden attributable to irrigation ? Malaria • In Africa South of the Sahara – irrigation introduction in areas of stable transmission no change or a reduction in transmission ("paddies paradox") – for a number of speculated reasons. (Mali, Burkina Faso, Sénégal) • In areas of unstable transmission: irrigation introduction causes a shift from seasonal to perennial transmission and places a heavy burden on non-immune populations. (Burundi, Ethiopia)
What is the fraction of the burden attributable to irrigation ? Malaria • In South and Southeast Asia: significant increases in malaria transmission (up to 5-fold increases) (Pakistan, Iran, India, Sri Lanka) • Coastal areas of South and Southeast Asia: malaria transmission linked to shrimp and fish farming (Viet Nam, Indonesia)
What is the fraction of the burden attributable to irrigation ? Lymphatic filariasis • Complex picture because of many contextual determinants at the local level and a dearth of datasets • Long incubation period, the entire disease burden stems from disability • An estimated 213 million people in endemic countries at risk in irrigated areas
What is the fraction of the burden attributable to irrigation ? Japanese encephalitis • Limited distribution • 1.9 billion people at risk • Critical contextual determinants: surface irrigation for rice production; pigs; ardeid birds; poor access • Several options for "agricultural type" interventions: improved irrigation water management (AWDI), biological control, IPM and IVM, economic (des)-incentives to reduce pig rearing.
What is the fraction of the burden attributable to irrigation ? Schistosomiasis • 779 million people at risk • In West Africa: pronounced impact on intestinal schistosomiasis, Sénégal from 0% to 71.8% prevalence rate following the construction of the Diama barrage • In Central Africa: a marked impact of irrigation development on the prevalence of urinary schistosomiasis (3-4 fold) • In East Africa: the irrigation development related spread of S. mansoni • In southern Africa: no conclusive evidence for a lack of solid datasets • (Iran: the resilience of environmental engineering measures)
Agricultural driving forces and determinants Health and environment cause-and-effect framework Driving force Population Economic Technology growth development Pressure Production Consumption Waste release State Natural hazards Resource Pollution levels availability Exposure External exposure Absorbed dose Target organ dose Vector density Vector longevity Human-vector contact frequency Effect Well-being Morbidity Mortality Action Impact assessment Risk management Health sector response
Agricultural driving forces and determinants Environmental determinants Hydrological changes introduction of irrigation intensification of irrigation impoundments, reservoirs, night storage water for livestock (small dams) fish ponds coastal areas (mangroves shrimp ponds)
Agricultural driving forces and determinants Environmental determinants Changes in land use patterns plot size cropping intensity and patterns settlement siting vis-à-vis agricultural lands livestock distribution chemical inputs (pesticides, fertilizers)
Agricultural driving forces and determinants Social determinants Changes in social structure income levels and distribution and process consumption patterns gender roles nutritional status migration (seasonal, re-settlement) subsistence vs cash crops mechanization
The impact of ill-health on agriculture Undermining the human resource base • loss of production capacity • school absentee-ism • pressure on gender roles • opportunity costs
The impact of ill-health on agriculture Poverty induced vicious circle • insufficient economic foundation to meet basic needs (including under-nutrition) • environmental degradation depleting the agricultural resource base • no resources to purchase essential agricultural inputs or upgrade production process • no access to health services
A combination of Burden of Disease estimates and cost-effectiveness analyses can differentiate those water interventions that give poor largest incremental health gains for least possible costs. Recent WHO analyses to attribute a disease burden to water, sanitation and hygiene risk factors show they account for: • 2.1 million deaths each year (3.9% of total) • 76 million DALYs lost each year (5.3% of total)
A combination of Burden of Disease estimates and cost-effectiveness analyses can differentiate those water interventions that give the poor largest incremental health gains for least possible costs. Maximum health gains in absolute terms: • provide the most basic water supply services to those who have no access at all • provide water supply and sewage connection to individual households Most cost-effective interventions: • Disinfection at point-of-use through chlorine treatment and safe storage vessels combined with limited hygiene education • Targeting key behavioural change (hand washing)
WHO links and action Current focus of the WHO Water Sanitation and Health programme with respect to irrigation and dams: Water Resources Development and Management • Assisting countries in IWRM policy development to ensure human health considerations are incorporated • National capacity building for Health Impact Assessment and Health Risk Management of water resources projects • Backstopping Member States with HIA Terms of Reference and Appraisals of specific water projects • Promoting research on water management measures for health protection and promotion
WHO links and action The WHO/FAO/UNEP Panel of Experts on Environmental Management for Vector Control (1981-1996): Objective: to establish an effective inter-agency and intersectoral framework for the promotion of environmental management for vector control in the context of agriculture, health and nature conservation programmes
WHO links and action The WHO/FAO/UNEP Panel of Experts on Environmental Management for Vector Control (1981-1996): • Technical reviews through annual Panel meetings • Guidelines development and promotion • Setting multidisciplinary research agendas and promoting research on EMVC • Capacity building, in particular skill development on intersectoral decision making Some key products: Strengthened knowledge base on the links between rice production systems and malaria/schisto in W-Africa (the WARDA/PEEM/IDRC project 1993-1998) A comprehensive Health Impact Assessment capacity building package, tested in five countries and currently being implemented in the Mekong area
WHO links and action Current collaboration with UNEP: Health and Environment Linkages Initiative (HELI) • Encourages developing country policy makers to support action on environmental threats to health • Sponsored by the Canadian Government, implemented by WHO and UNEP • Range of case studies at countries level (incl. Uganda, Thailand and Brazil) including health issues in agricultural settings • Priority areas: vector-borne diseases, the urban environment, indoor air pollution and household energy, water-health-ecosystems, climate change and toxic substances Collaboration with FAO in this area has declined, but continues in other areas such as food safety, Codex alimentarius, veterinary public health (bird flu) and water legislation
WHO links and action Links with the CGIAR system: IRRI 1987 workshop 1988-1992 proposal development, collapsed for lack of donor interest Work on pesticides and their impact on the health of rice farmers, links between IPM and IVM
WHO links and action Links with the CGIAR system: IWMI 1985 workshop in Digana Village (irrigation and malaria) Establishment of the Health and Environment department Creation of SIMA Dialogue on Water for Food and the Environment Research on malaria, JE and irrigation in Asia; malaria and urban agriculture in Ghana; health aspects of waste water use
WHO links and action Links with the CGIAR system: WARDA 1992-1998 Consortium Research project on the Association between Irrigated Rice Production Systems and Malaria/Schistosomiasis in West Africa Nine papers published in the biomedical literature Supported by IDRC, Govnmts of Denmark and Norway
WHO links and action Links with the CGIAR system: ISNAR Review of irrigation related malaria in the Causasian countries Work on alternatives to POPs pesticides for public health purposes
ISSUES FOR DISCUSSION How to expand our knowledge base on the (cost-) effectiveness on water management, environmental management and similar interventions in specific contexts in an efficient way ?
ISSUES FOR DISCUSSION How to mainstream the outcomes of case studies and intervention studies into the international and national agricultural policy frameworks ?
ISSUES FOR DISCUSSION The need to clarify the economics of agriculture/health linkages and of intersectoral interventions for health protection and promotion in the setting of agricultural production systems.
ISSUES FOR DISCUSSION Optimizing the delivery of health messages to farmers with a focus on improved environmental management and best practice in irrigation and other agricultural activities: technical content, intersectoral mechanisms, the credibility issue