Transcript PRESENTATION_ Lyme Disease_UVA

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
Lyme disease
• Hosts:
humans, dogs, horses
Deer
Chipmunks, mice
• Vectors:
Black-legged ticks
Ixodes scapularis, Ixodes
pacificus
Lyme disease hosts [9]
Pathogenesis of Lyme disease
Nymph
Osp A dormant
Nymph
Osp C Active
Skin:
Erythema
migrans (335) days
cerebral spinal
fluid, brain,
retina, liver,
Joints –
myositis, facial
palsy, cardiac
conductance
abnormalities,
arthritis
Erythema
migrans in
Lyme
patients,
MDH
Lyme disease: climate
• Ashley and
Meentemeyer, 2004.
Richard Ostfield, 2000
– Average temp 10.8oC
(50oF) and 19.4oc (70oF)
– Total precipitation
between 19.7cm (7.7
inches) and 37.8cm (14.9
inches).
NE & Mid-west USA: 94 99
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
Allan, Keesing, Ostfield,
2003.
Forest fragmentation
• < 2 ha
• High nymph
density
• High mice
population
• Low vertebrate
hosts
• High density of
infected nymphs
Habitat for black legged ticks
Adapted from (MDH)
Woody and bushy habitat
Provides food and cover
for hosts like mice and
deer (MDH).
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
• To describe the distribution of Lyme disease
cases in North Dakota, Minnesota and
Wisconsin from 1990 to 2010
Objective 1
Human Lyme cases in ND, MN
and WI
• 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
Objective 2
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
Variable
Pr > |t|
Average summer temperature
DF Estimate Standard t
Error
Value
1
53.577
36.23
1.48
Total summer precipitation
1
-33.501
42.77
-0.78
0.4370
Duration of Summer
temperatures
Annual precipitation
1
30.642
93.84
0.33
0.7453
1
82.742
35.87
2.31
0.0250
Total Winter precipitation
1
-41.481
35.74
-1.16
0.2510
Average winter temperature
1
-11.258
14.38
-0.78
0.4371
Total spring precipitation
1
-104.04
64.73
-1.61
0.1139
Average spring temperature
1
-9.972
9.89
-1.01
0.3178
Total fall precipitation
1
-95.66
57.44
-1.67
0.1018
Average fall temperature
1
61.06
25.21
2.42
0.0189
0.1451
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
References
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Research, 27: 177–187.
FMD Reference Laboratories Information System - ReLaIS , http://www.foot-and-mouth.org/
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