Small scale irrigation and malaria in Ziway, Ethiopia

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

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  • Small scale irrigation and malaria in Ziway, Ethiopia

    1. 1. Eline Boelee, Solomon Kibret, Beyene Petros, Yihenew Alemu EcoHealth Forum Merida, Mexico 2 December 2008 Small scale irrigation and malaria in Ziway, Ethiopia
    2. 2. <ul><li>Part of Austria-funded research project on impacts of irrigation on poverty and environment in Ethiopia </li></ul><ul><li>Study based on 2 MSc theses, Biology Department, Addis Ababa University </li></ul><ul><li>Co-funded by CGIAR Systemwide Initiative on Malaria and Agriculture (SIMA) </li></ul>Partners and funding
    3. 3. <ul><li>Objective: evaluate the impact of a small-scale irrigation scheme in Central Ethiopia on malaria transmission </li></ul><ul><li>Classic biomedical approach </li></ul><ul><li>MSc Epidemiology: parasitological survey and socio-economic questionnaire </li></ul><ul><li>MSc Entomology: adult and larval sampling, ELISA tests </li></ul><ul><li>Would we have gotten other results using EcoHealth approach? </li></ul>Set-up of the study
    4. 4. Study area - 1 Source: S.Kibret, 2008
    5. 5. <ul><li>Ziway in Central Rift Valley </li></ul><ul><li>P = 700-800 mm, bimodal; mean T = 20 °C </li></ul><ul><ul><li>heavy rains in June - September </li></ul></ul><ul><ul><li>short rains in April and May </li></ul></ul><ul><li>Seasonal malaria transmission (unstable) </li></ul><ul><ul><li>Peak transmission September – November </li></ul></ul><ul><ul><li>Second minor transmission April / May </li></ul></ul><ul><li>Plasmodium falciparum accounts for 60-70% of malaria cases, vivax malaria less prevalent </li></ul><ul><li>Anopheles arabiensis is primary vector, An. pharoensis secondary </li></ul>Study area - 2
    6. 6. <ul><li>Two villages </li></ul><ul><ul><li>Altitude around 1650 m </li></ul></ul><ul><ul><li>Subsistence farming </li></ul></ul><ul><ul><li>Livestock important, often indoors at night </li></ul></ul><ul><li>Abene Girmamo – irrigation </li></ul><ul><ul><li>Population size 950 </li></ul></ul><ul><ul><li>Human / Livestock ration 1: 0.4 </li></ul></ul><ul><ul><li>Onion, cabbage, tomato and maize </li></ul></ul><ul><li>Woshgulla – no irrigation </li></ul><ul><ul><li>Population size 741 </li></ul></ul><ul><ul><li>Human / Livestock ration 1: 0.6 </li></ul></ul>Study area - 3
    7. 7. <ul><li>Epidemiology </li></ul><ul><ul><li>Thick & thin blood smears (finger prick) by technicians </li></ul></ul><ul><ul><ul><li>Transmission season September/October 2005 </li></ul></ul></ul><ul><ul><ul><li>Dry season January/February 2006 </li></ul></ul></ul><ul><li>Questionnaire </li></ul><ul><ul><li>Household, farm size, income, agricultural system, livestock, housing </li></ul></ul><ul><li>Entomology </li></ul><ul><ul><li>Larval and adult mosquito sampling </li></ul></ul><ul><ul><ul><li>Dry season January/February 2006 </li></ul></ul></ul><ul><ul><ul><li>Short rainy season April/May 2006 </li></ul></ul></ul><ul><ul><li>Larvae: standard 350 ml dipper </li></ul></ul><ul><ul><li>Adults: CDC light traps, aspirator, spray catches, ELISA tests </li></ul></ul>Sampling methods
    8. 8. <ul><ul><li>Higher transmission in village with irrigation, especially in dry season </li></ul></ul><ul><ul><li>P. falciparum main parasite </li></ul></ul><ul><ul><li>Income, type of house, malaria history significant variables </li></ul></ul>Results - epidemiology 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 195 (16.1) 1208 232 (18.9) 1227 Overall 59 (11.4) 516 120 ( 22.7 ) 528 Dry season 136 ( 19.6 ) 692 112 (16.0) 699 Wet season Positive (%) N Positive (%) N Woshgulla (rain-fed) Abene Girmamo (irrigation)
    9. 9. <ul><li>An. pharoensis most prevalent </li></ul><ul><li>Higher mosquito densities in more breeding sites in irrigated area (80% in irrigation habitats) </li></ul>Results – mosquito larvae Source: Graph created by E.Boelee based on data from S.Kibret, 2008 Photo Credit: Solomon Kibret
    10. 10. <ul><ul><li>Higher mosquito densities in village with irrigation </li></ul></ul><ul><ul><li>Higher densities in dry season </li></ul></ul><ul><ul><li>An. pharoensis and An. coustani more outdoors </li></ul></ul><ul><ul><li>An. arabiensis more indoors </li></ul></ul>Results – adult mosquitoes Source: S.Kibret, 2008 Woshgulla (rain-fed) 0 0 0 Wet season 16 4 38 Dry season Abene Girmamo (irrigation) 170 552 491 Overall 4 212 340 An. pharoensis 38 309 182 An. arabiensis 16 Overall 94 Dry season 76 Wet season An. coustani
    11. 11. Results – biting peaks An. arabiensis An. pharoensis An. coustani Source: S.Kibret, 2008
    12. 12. <ul><li>Human Blood Index (HBI) determined for Abene Girmamo (irrigation) village only </li></ul><ul><li>No mosquitoes tested positive in rain-fed village and none positive for P. vivax </li></ul><ul><li>Higher sporozoite rates in short rainly season </li></ul><ul><li>An. arabiensis and An. pharoensis most important anthropophagic vector species </li></ul>Results – HBI & SR Source: S.Kibret, 2008 SR HBI 424 120 N 1.18% 0.78 value An. arabiensis 131 16 N 0 0.06 Value An. coustani An. pharoensis value N 0.69 142 0.59% 509
    13. 13. <ul><li>Irrigation system provides breeding sites for year-round and increased transmission of malaria in Ziway area, Ethiopia </li></ul><ul><li>An. arabiensis and An. pharoensis most important anthropophagic vector species, breeding all year </li></ul><ul><li>Higher infection rates among irrigating farmers possibly caused by evening outdoor work </li></ul><ul><li>Vector breeding sites associated with poorly maintained canals and hydraulic structures </li></ul><ul><li>Trend of earlier biting peak An. arabiensis confirmed – risky for children and adults </li></ul>Discussion and Conclusions
    14. 14. <ul><li>Additional studies to capture seasonal and spatial differences </li></ul><ul><li>With early biting peaks, alternatives to bed nets required </li></ul><ul><li>Environmental water management for source reduction </li></ul>Recommendations <ul><li>What could EcoHealth approach bring as added value? </li></ul>Photo Credit: Solomon Kibret
    15. 15. Thank you More info: e.boelee@cgiar.org http://www.iwmi.cgiar.org/Publications/index.aspx http://www.doi.org/10.1111/j.1365-3156.2009.02423.x

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