small scale irrigation and malaria in ziway, ethiopia

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Ecohealth Forum 2Dec08 Eline Boelee, Solomon Kibret, Beyene Petros, Yihenew Alemu EcoHealth Forum Merida, Mexico 2 December 2008 Small scale irrigation and malaria in Ziway, Ethiopia

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Small scale irrigation and malaria in Ziway, EthiopiaEline Boelee, Solomon Kibret, Beyene Petros, Yihenew AlemuEcoHealth ForumMerida, Mexico2 December 2008

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Page 1: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

Eline Boelee, Solomon Kibret, Beyene Petros, Yihenew Alemu

EcoHealth ForumMerida, Mexico

2 December 2008

Small scale irrigation and malaria in Ziway, Ethiopia

Page 2: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

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)

Page 3: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

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?

Page 4: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

Study area - 1

Source: S.Kibret, 2008

Page 5: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

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

Page 6: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

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

Page 7: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

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

Page 8: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

Results - epidemiology

• Higher transmission in village with irrigation, especially in dry season

• P. falciparum main parasite• Income, type of house, malaria

history significant variables

Abene Girmamo(irrigation)

Woshgulla(rain-fed)

N Positive (%) N Positive (%)

Wet season 699 112 (16.0) 692 136 (19.6)

Dry season 528 120 (22.7) 516 59 (11.4)

Overall 1227 232 (18.9) 1208 195 (16.1)

negative82%

P. falciparum13%

P. vivax5%

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

Page 9: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

Results – mosquito larvae

• An. pharoensis most prevalent• Higher mosquito densities in more breeding sites

in irrigated area (80% in irrigation habitats)

0

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Brick-makingpits (n=5)

Canalleakage

pools (n=12)

Irrigated fieldpuddles(n=23)

Irrigationcanals (n=4)

Rain pools(n=7)

Brick-makingpits (n=7)

Rain pools(n=4)

Waterharvestingpools (n=1)

Abene Girmamo (irrigation) Woshgulla (rain-fed)

An. arabiensis

An. pharoensis

An. coustani

Source: Graph created by E.Boelee based on data from S.Kibret, 2008

Photo Credit: Solomon Kibret

Page 10: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

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

An. arabiensis An. pharoensis An. coustani

Abene Girmamo (irrigation)

Wet season 182 340 76

Dry season 309 212 94

Overall 491 552 170

Woshgulla (rain-fed)

Wet season 0 0 0

Dry season 38 4 16

Overall 38 4 16Source: S.Kibret, 2008

Page 11: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

Results – biting peaks

0.0

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Indoors (n = 24 light trap-nights)

Outdoors (n = 24 light trap-nights)

An. arabiensis

An. pharoensis

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1800-1900

1900-2000

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Indoors (n = 24 light trap-nights)

Outdoors (n = 24 light trap-nights)

An. coustani

0.0

10.0

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1800

-190

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Indoors (n = 24 light trap-nights)Outdoors (n = 24 light trap-nights)

Source: S.Kibret, 2008

Page 12: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

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

An. arabiensis An. pharoensis An. coustani

N value N value N Value

HBI 120 0.78 142 0.69 16 0.06

SR 424 1.18% 509 0.59% 131 0Source: S.Kibret, 2008

Page 13: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

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

Page 14: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

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

Page 15: Small scale irrigation and malaria in Ziway, Ethiopia

Ecohealth Forum 2Dec08

Thank youThank you

More info: [email protected]

http://www.iwmi.cgiar.org/Publications/index.aspx

http://www.doi.org/10.1111/j.1365-3156.2009.02423.x