Presentation on theme: "Multi-factorial predispositions to emerging infectious diseases: A case of land cover and weather changes and their role in the increased occurrence of."— Presentation transcript:
Multi-factorial predispositions to emerging infectious diseases: A case of land cover and weather changes and their role in the increased occurrence of Lyme disease in North Dakota Michael Muleme; Anthony W. Wamono; Eugene S. Berry; Margaret L. Khaitsa
OUTLINE Introduction –Review on Lyme disease Methodology Results and Discussion Conclusions
Lyme disease Most commonly reported vector borne disease in U.S., Europe and Asia Cause: Borrelia burgdorferi – U.S.A B. afzelii and B. garinii – Asia All the three species – Europe Diagram of Borrelia burgdorferi, MDH
Pathogenesis of Lyme disease Erythema migrans in Lyme patients, MDH
Lyme disease: climate Ashley and Meentemeyer, 2004. – Average temp 10.8 o C (50 o F) and 19.4 o c (70 o F) – Total precipitation between 19.7cm (7.7 inches) and 37.8cm (14.9 inches). NE & Mid-west USA: 94 - 99 Richard Ostfield, 2000
Lyme disease: climate McCabe and Bunnel, 2004 :Correlation between climate and Lyme disease, 1992-2002, NE and MW US Dark dots show significance at 95% CI Early spring and summer precipitation were significant
Lyme disease: Environment Habitat for black legged ticks Adapted from (MDH) Woody and bushy habitat Provides food and cover for hosts like mice and deer (MDH). Allan, Keesing, Ostfield, 2003. Forest fragmentation < 2 ha High nymph density High mice population Low vertebrate hosts High density of infected nymphs
Objectives of the study To describe the distribution of Lyme disease cases in North Dakota, Minnesota and Wisconsin from 1990 to 2010 To assess the influence of climate (temperature and precipitation) and the environment on the occurrence of the disease in North Dakota, Minnesota and Wisconsin
Methodology Data sources Lyme cases –MNDH, WIDH and NDDH –VDL – Animal Lyme cases Climate –NOAA Land use –NASS Human Population –US Census 2010 Data Analysis –Multiple regression, SAS procedure –Arc GIS
Objective 1 To describe the distribution of Lyme disease cases in North Dakota, Minnesota and Wisconsin from 1990 to 2010
Objective 2 To evaluate the influence of climate and environmental factors on the occurrence of Lyme disease cases in North Dakota, Minnesota and Wisconsin from 1990 to 2010
Climate and Lyme disease in ND, MN and WI, 1990-2010 Mean Temperature summer 63.65 – 72.70 (ND),63.15 – 72.70 (MN), 65.71 – 74.19 (WI) winter 7.31 – 20.32 (ND) 9.36 – 22.06 (MN), 17.47 – 29.18 (WI) Fall 39.15 – 47.04 (ND), 39.15 – 47.83 (MN), 2.52 – 8.15 (WI) Spring 35.48 – 45.93 (ND), 36.85 – 48.22 (MN), 41.50 – 50.34 (WI)
Climate and Lyme disease in ND, MN and WI, 1990-2010 Annual Precipitation ND - 13.72 – 25.44 inches MN 22.56 – 35.79 inches WI 26.81 – 39.60 inches
Multiple regression analysis of climate variables and Lyme cases VariableDFEstimate Standard Error t Value Pr > |t| Average summer temperature153.57736.231.480.1451 Total summer precipitation1-33.50142.77-0.780.4370 Duration of Summer temperatures 130.64293.840.330.7453 Annual precipitation182.74235.872.310.0250 Total Winter precipitation1-41.48135.74-1.160.2510 Average winter temperature1-11.25814.38-0.780.4371 Total spring precipitation1-104.0464.73-1.610.1139 Average spring temperature1-9.9729.89-1.010.3178 Total fall precipitation1-95.6657.44-1.670.1018 Average fall temperature161.0625.212.420.0189
Land-use changes in ND, MN and WI Forest land coverage ranged 500,000 – 1000,000 acres in ND, 12,000,000 – 16,000,000 acres in MN and from 13,500,000 – 16,000,000 acres in WI. Shrub land cover increased in ND to above 1000,000 acres while that in WI and MN fluctuated below 1000,000 acres.
Land use and human population Increase in human population Increased incidence of Lyme disease
General remaks –Increase in Average fall temperatures results in a prolonged activity of ticks –High annual precipitation results in increased tick survival –Forests and shrub lands support tick, mice and vertebrate host species. –Increased population results in increased human exposure to ticks.
Conclusion Increase in total annual precipitation (P = 0.025) and average fall temperatures (P = 0.0189) were significantly associated with the increased occurrence of Lyme disease in ND, MN, WI. Increase in shrub land, forest and woody wetland coverage in ND, which are reported to favor proliferation of ticks, deer and small mammals could be contributing factors to the increased cases of Lyme disease.
Acknowledgements Graduate committee: Dr. Margaret Khaitsa Dr. Peter Oduor Dr. Penelope Gibbs Anthony W. Wamono Curt Doetkott Prof. J D Kabasa and Margaret L. Khaitsa PI USAID/HED Grant
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