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Climate Change, GIS, and Vector- Borne Disease Jessica Beckham February 10, 2011
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Climate change and human health: present and future risks Anthropogenic greenhouse gas emissions Increased temp by 2100 1.4-5.8 C Increased annual global rainfall Drier climate in some regions More severe flooding and precipitation in other regions ENSO
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Effects on Vector-borne Infections Incidence Seasonal transmission Geographic Range Social, economic, topographic conditions?
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Range Predictions of Aedes aegyptii
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The El Nino Southern Oscillation and malaria epidemics in South America Possibility of using ENSO forecasts to improve malaria control Statistical methods look for relationship between ENSO and malaria epidemics 1956-1998 Malaria associated with flooding AND drought Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, Venezuela, Brazil
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Four Null Hypotheses: Malaria epidemics are not more likely to occur in a) Nino vs. other years b) Nino +1 vs. other years c) either Nino or Nino+1 vs. other years d) La Nina vs. other years Test: Fisher’s exact (contingency table) p-value: probability that variation is due to random chance; level of significance = 0.05
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Results
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The El Nino Southern Oscillation and the historic malaria epidemics on the Indian subcontinent and Sri Lanka Punjab region and former Ceylon, a.k.a. Sri Lanka 1868-1943 Periodic epidemics associated with ENSO/ monsoon fluctuations
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Punjab Rainfall
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Sri Lanka Rainfall
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Monsoon Rainfall (June-Sept) Monsoon rainfall = sum of all weighted values from meteorological stations divided by area of subdivision for each year
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“Epidemic Figure” Avg monthly “fever deaths” Oct-Dec: Avg monthly fever deaths April-July Administrative records Oct-Dec = most malaria deaths occur 1867-1943 EFs calculated EF over 2 = epidemic year “fever deaths” due to other causes?
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Malaria Epidemic Years -”epidemic figure” -Chi-Square Test Statistic; 1 df -in Punjab, 47.6% prob of epidemic in Nino+1 yr vs. 10.7% in other yrs (chi-square = 12.6; p<0.001) (time period 1867-1943; 1905-1943 showed no significant difference) -in Sri Lanka, 45.0% prob of epidemic in Nino yrs vs. 12.5% in other yrs (chi-square = 9.43; p<0.005)
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Conclusions Malaria mortality and elevated monsoon rainfall correlated with ENSO Dry year followed by wet year = more risk for epidemic Economic stress = more risk for epidemic
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Prediction of a Rift Valley Fever outbreak RVF = viral, mosquito-borne Affects humans, domestic animals Outbreaks linked to ENSO Horn of Africa Dambos Satellite remote sensing data Risk Map for 2006-2007
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SST Anomalies
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OLR Anomalies
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Rainfall Anomalies
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Vegetation (NDVI) Anomalies
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RVF Risk Map
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Conclusions Rainfall and vegetation anomalies = ideal conditions for mosquito vector Predicted RVF outbreak in Horn of Africa (64% of cases fell within risk map area) Implications for future
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