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Small scale irrigation and malaria in Ziway, Ethiopia

Small scale irrigation and malaria in Ziway, Ethiopia. Eline Boelee, Solomon Kibret, Beyene Petros, Yihenew Alemu EcoHealth Forum Merida, Mexico 2 December 2008. Partners and funding. Part of Austria-funded research project on impacts of irrigation on poverty and environment in Ethiopia

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Small scale irrigation and malaria in Ziway, Ethiopia

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  1. Small scale irrigation and malaria in Ziway, Ethiopia Eline Boelee, Solomon Kibret, Beyene Petros, Yihenew Alemu EcoHealth Forum Merida, Mexico 2 December 2008

  2. Partners and funding • Part of Austria-funded research project on impacts of irrigation on poverty and environment in Ethiopia • Study based on 2 MSc theses, Biology Department, Addis Ababa University • Co-funded by CGIAR Systemwide Initiative on Malaria and Agriculture (SIMA)

  3. Set-up of the study • Objective: evaluate the impact of a small-scale irrigation scheme in Central Ethiopia on malaria transmission • Classic biomedical approach • MSc Epidemiology: parasitological survey and socio-economic questionnaire • MSc Entomology: adult and larval sampling, ELISA tests • Would we have gotten other results using EcoHealth approach?

  4. Study area - 1 Source: S.Kibret, 2008

  5. Study area - 2 • Ziway in Central Rift Valley • P = 700-800 mm, bimodal; mean T = 20 °C • heavy rains in June - September • short rains in April and May • Seasonal malaria transmission (unstable) • Peak transmission September – November • Second minor transmission April / May • Plasmodium falciparum accounts for 60-70% of malaria cases, vivax malaria less prevalent • Anopheles arabiensis is primary vector, An. pharoensis secondary

  6. Study area - 3 • Two villages • Altitude around 1650 m • Subsistence farming • Livestock important, often indoors at night • Abene Girmamo – irrigation • Population size 950 • Human / Livestock ration 1: 0.4 • Onion, cabbage, tomato and maize • Woshgulla – no irrigation • Population size 741 • Human / Livestock ration 1: 0.6

  7. Sampling methods • Epidemiology • Thick & thin blood smears (finger prick) by technicians • Transmission season September/October 2005 • Dry season January/February 2006 • Questionnaire • Household, farm size, income, agricultural system, livestock, housing • Entomology • Larval and adult mosquito sampling • Dry season January/February 2006 • Short rainy season April/May 2006 • Larvae: standard 350 ml dipper • Adults: CDC light traps, aspirator, spray catches, ELISA tests

  8. Results - epidemiology • Higher transmission in village with irrigation, especially in dry season • P. falciparum main parasite • Income, type of house, malaria history significant variables Source: Table compiled by E.Boelee based on data from Y.Alemu,2007 Source: Pie-chart created by E.Boelee based on data from Y.Alemu,2007

  9. Results – mosquito larvae • An. pharoensis most prevalent • Higher mosquito densities in more breeding sites in irrigated area (80% in irrigation habitats) Source: Graph created by E.Boelee based on data from S.Kibret, 2008 Photo Credit: Solomon Kibret

  10. Results – adult mosquitoes • Higher mosquito densities in village with irrigation • Higher densities in dry season • An. pharoensis and An. coustani more outdoors • An. arabiensis more indoors Source: S.Kibret, 2008

  11. Results – biting peaks An. arabiensis An. pharoensis An. coustani Source: S.Kibret, 2008

  12. Results – HBI & SR • Human Blood Index (HBI) determined for Abene Girmamo (irrigation) village only • No mosquitoes tested positive in rain-fed village and none positive for P. vivax • Higher sporozoite rates in short rainly season • An. arabiensis and An. pharoensis most important anthropophagic vector species Source: S.Kibret, 2008

  13. Discussion and Conclusions • Irrigation system provides breeding sites for year-round and increased transmission of malaria in Ziway area, Ethiopia • An. arabiensis and An. pharoensis most important anthropophagic vector species, breeding all year • Higher infection rates among irrigating farmers possibly caused by evening outdoor work • Vector breeding sites associated with poorly maintained canals and hydraulic structures • Trend of earlier biting peak An. arabiensis confirmed – risky for children and adults

  14. Recommendations • Additional studies to capture seasonal and spatial differences • With early biting peaks, alternatives to bed nets required • Environmental water management for source reduction • What could EcoHealth approach bring as added value? Photo Credit: Solomon Kibret

  15. More info: e.boelee@cgiar.org Thank you http://www.iwmi.cgiar.org/Publications/index.aspx http://www.doi.org/10.1111/j.1365-3156.2009.02423.x

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