Lyme Disease and West Nile VirusRisk Assessment Aberdeen Proving Ground,

Edgewood Area

Thomas M. Kollars, Jr., PhD

Entomological Sciences Program, CHPPM

Lyme Disease Risk Model• 1. Study conducted June 2001 through April 2002• 2. Sites – 10 areas, 3 habitats

– Wooded– Ecotone– Field

• 3. Environmental Variables– Elevation (min, max, mean)– Habitat Type– Tree Density– Canopy Cover– Shrub– Herbaceous– Monocot– Fern

Regression Analysis of adult I. scapularis and Habitat Variables

Based upon shrub density as correlated with adult Ixodes scapularis using regression model

When mean of 200 sample points are used/10m intersect

R sqr. =0.87

F (1, 18)=120

P<0.001

Lyme Disease Risk Assessment Edgewood Area from adult Black-legged Ticks

>1 Tick

>.5 and < 1 Tick

< .5 Tick

Accuracy of Lyme Disease Risk Model based on shrub density

Model tested in March/April 200234 sites 2m2 dragged

1= <17 shrub 2= 17-25 3>25 shrubs

• Mpb Matapex silt loam 2%-5% slope, mean 0.57

• Roa Romney and Elkton soils, cratered, mean 0.32

• Ud Udorthents, loamy, 0 to 10 % Slopes, mean 0.12

• BeB Beltville silt loam, 2 to 5 % slopes, mean 0.23

• MU Mattapex-Udorthents-Urban, 0 to 2 % slope, mean 0.00

• BeA Beltville silt loam, 0 to 2 % slopes, mean 1.00

• Ot Othello silt loam, mean 0.0

Comparison of adult I. scapularis among soil types using ANOVA and LSD (where > 6 samples were taken)

Risk assessment of adult I. scapularis based on soil type at Edgewood area (APG) (p<0.05)

1 tick per 4m2

1 tick per 9m2

1 tick per 17m2

Risk Assessment Map of Aberdeen Proving Ground based upon extrapolated adult Black-legged Tick and Soil Classification

1 tick per 4m2

1 tick per 9m2

1 tick per 17m2

West Nile Risk Assessment

• 10 study areas, 3 habitats each 2001

• June 0330 –0730 identify bird species

• July through October - Landing counts 0600-0730

• Model using Sugeno and Takagi Fuzzy Reasoning

West Nile Virus Risk Assessment

Mosquito Feeding and Flight Behavior

West Nile Virus Potential At Edgewoodbased upon Sugeno and Takagi Fuzzy Reasoning

 Bird Risk = (fuzzy (wnv antibody x flock))

= BRMosquito Risk = (fuzzy (ornithophilic x homophilic)) = MR

 1 = BR1(BRO) MR1(MRO)

min {High (BRO), High (MRO)}

= 0.752 = BR2(BRO) MR2(MRO)

= min {Moderate (BRO), Moderate (MRO)}

= 0.5 

High WNVP1 = High (BRO) + High (MRO)

= 1.60 + 2.05= 3.65

Moderate WNVP2 = Moderate (BRO) + Moderate (MRO)

= 1.40 + 1.37= 2.77

 Control Measures Should Be Implemented When WNVP =

0 = 11 + 22 / 1 + 2

= 4.12 / 1.25= 3.3

De-fuzzified WNV Risk at each Site

IPM Mosquito Control

Continuous Surveillance

Periodic Surveillance

West Nile Risk Assessment Edgewood AreaUsing Fuzzy Logic Model

Continuing Surveillance

• Tick-borne Disease surveillance– Continue to refine adult black-legged tick prediction

– Identify variables associated with immature tick populations

– Identify variables associated with other tick species

– Test infection rates of ticks by PCR

– Expand and test model at other installations

• Arbo-virus / West Nile Virus Surveillance– Continue to identify bird and mosquito species

– Test infection rates in mosquitoes by PCR

– Expand surveillance to other installations