People and Forest Patches: Residential exposure and Lyme disease in Southern New England

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People and Forest PatchesResidential exposure
and Lyme disease in Southern New England
Senior Thesis in Environmental Science Allan
Just April 19th, 2005
Source Sarah Leen
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People, Environment, and Lyme Disease
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Study Questions

• How does human interaction with tick habitats
  influence the public health risk of Lyme disease?

• What are the spatial patterns of disease?
• What is the role of potential habitat and
  residential exposure?

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Outline

• Study Question
• Public Health and Environmental Integrity
• Lyme Disease Introduction
• Ecology of Lyme Disease
• Human Exposure and Risk
• Study Design
• Data Sources
• Variable construction and analysis
• Results
• Visualizing the human risk of Lyme disease
• The importance of residential exposure
• Implications and Future Directions

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Ecology of Lyme Disease

• Agent
• Borrelia burgdorferi
• Spirochete
• Vector
• Ixodes Scapularis
• Deer Tick
• Host
• Reservoir

Source Centers for Disease Control
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Bloodmeals
Source American Lyme Disease Foundation
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Lyme Disease Burden

• 23,763 cases of Lyme disease nationally in 2002
• Pathology
• Acute - bulls eye rash
• Chronic Joint inflammation
• Neurological symptoms
• Rare - Cardiac symptoms

Source CDC Lyme Disease MMWR Jan 18,
2002/51(02)
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Tick Habitat Characteristics

• Eco Approach
• Focused on Ecology and Entomology
• Usually limited to small areas and short sampling
  season
• Often focus on entomologic indices of human risk
• ?

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Tick Habitat Characteristics

• Eco Approach
• Focused on Ecology and Entomology
• Usually limited to small areas and short sampling
  season
• Often focus on entomologic indices of human risk
• Characteristics of where ticks are found
• Deciduous Forest
• Nearby Ornamentals and Lawns
• Smaller Patches?
• Sandy Soils?
• Near Water?

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Human Exposure

• Public Health Approach
• studies focus on individual human behaviors and
  nearby habitat
• Case-control designs are limited in area and
  numbers
• Exposure characterized in the northeast as
  Peridomestic
• Distance from residence to forest is important
• Also recreational and occupational exposures
  beyond the home

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Outline

• Study Question
• Public Health and Environmental Integrity
• Lyme Disease Introduction
• Ecology of Lyme Disease
• Human Exposure and Risk
• Study Design
• Data Sources
• Variable construction and analysis
• Results
• Visualizing the human risk of Lyme disease
• The importance of residential exposure
• Implications and Future Directions

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Study Area and Population

• Southern New England
• Connecticut
• Rhode Island
• Massachusetts
• All residents from 1998-2002
• 559 Cities and Towns

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Data Sources

• Lyme Disease Cases
• MA Department of Public Health
• RI Department of Health
• CT Department of Public Health
• Nationally Notifiable Disease since 1991
• Uniform Case Definition

The author is not affiliated with the
Massachusetts Department of Public Health and the
Department of Public Health is not responsible
for the accuracy and validity of the results
presented. The views stated are not necessarily
those of the Department.
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Data Sources

• Land Cover
• National Land Cover Dataset 1992
• 30 x 30 meter pixel size
• Demographics
• US Census 2000
• Block level smallest spatial unit Average 73
  persons

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Variable Construction

• Multi-state GIS, Raster Overlay

Land Cover
Census Population Density

• An Example Urban-to-Rural transect of Towns in
  Rhode Island

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Zooming in
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Population Density
Rural
Urban
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Land Cover
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Increasing Proportion of town area classified as
deciduous forest
67 55
43 3
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Increasing Proportion of the Population at 30m or
less from deciduous forest
85 74
37 2
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Results

• Visualizing Lyme Disease Cumulative Incidence
• Association with Deciduous Forest
• Residential Exposure Aggregates

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Deciduous Forest and Cumulative Incidence of Lyme
disease
Relative Rate 13 (10 to 16)
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Residential Exposure Aggregates and Cumulative
Incidence of Lyme disease
Relative Rate 26 (20 to 34)
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can we simply pave over the ticks
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can we simply pave over the ticks
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can we simply pave over the ticks
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can we simply pave over the ticks
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Comparison
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Comparison
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Comparison
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Further Steps

• Multivariate Modeling that accounts for rare
  disease outcome
• Stratify by Ecoregions to observe variation that
  may be abiotic
• Interpret more recent remotely sensed images for
  land cover, likely habitat, and the role of mixed
  pixels

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Benefits and Policy Implications

• Regional scale for decision making and
  prioritization
• Applicable to future endemic areas for prediction
• Promote compact development in town planning and
  at the state/regional level
• Add loss of health from disease to costs of
  sprawl

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Acknowledgments
Rachel Morello-Frosch Jen Hughes, Sally Zierler,
John Brownstein Bill Jesdale Lynn Carlson Tracy
LaPorte, Dr. Bandy Catherine Starr The Suite Noam
Ross Friends and Family The ES Community
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