Risk of exposure to Lyme disease in northern California Mixed Hardwood Woodland Grass Chaparral Grassland Nymphs 5-15% infected Adults 1-4% infected Mean number of infected ticks per 100 m 2 Caryl Waggett, Environmental Science, Allegheny College and Robert Lane, Insect Biology, University of California at Berkeley All residents spend an extraordinary amount of time outdoors, but residents who have been exposed to Bb spend statistically more time outdoors than non-exposed residents. Residents spend less time outdoors now than they did in Residents in rural northern California live adjacent to habitats at high risk from infected nymphs and along ecotones at moderate risk from infected adult ticks. Lyme disease is the most prevalent in the Northeast and Midwest, but high numbers of human cases have been identified in coastal northern California. Bb Exposed mean hrs/wk Bb Non-Exposed mean hrs/wk The Lyme disease spirochete, Bb, has a complicated life cycle involving two vectors and many hosts that affect risk of human exposure. The tick responsible for transmitting Bb to humans has definitive habitat preferences and seasonal distributions. Lyme disease Most prevalent vector-borne disease in the United States. Human incidence in California is patchy, reflecting underlying variability in vector density and infection prevalence Three-part study designed to identify high risk habitats, develop monitoring program and conduct epidemiological assessment of risk factors Ecological assessment Four dominant habitats (n=48) and ecotones (n=10) flagged for ticks Collected and analyzed >3,500 ticks bi-weekly over 3 years Acarolgic risk, the number of infected ticks/100 m 2, varied by: — Habitat, season, tick life stage Hardwood forests pose greatest risk of exposure to infected nymphs Ecotones and chaparral pose moderate risk to infected adults — Abiotic factors correlated with acarologic risk included: Aspect, slope, canopy, leaf duff, substrate, pH, relative humidity and temperature Monitoring Lyme disease risks Rapid changes in land use patterns in rural California CA population to double from to 60 million people Rural northern CA currently affordable, accessible Increased habitat fragmentation, development in high risk habitats Model developed using satellite imagery to characterize high risk habitats identified from ecological assessments Landsat TM5 imagery (30m resolution) from Nov 2002 Drought- and winter-deciduous trees had lost leaves 89 reference sites (1,792 pixels) from 5 habitats Hardwood forests, woodland grass, grass, chaparral, control = water Values from 6 non-thermal bands used to create habitat- specific reference signatures Each of 51 validation sites (351 pixels) were compared to reference signatures Each pixel characterized to habitat using root mean square (RMS) error with smallest difference Model re-run using Tasseled cap indices Greenness, wetness, brightness Band 4 Model results for monitoring Lyme disease risk High risk habitats not uniquely identifiable using satellite imagery Overall spectral signatures appear unique, but high band variability present within each habitat TM5 Model % AccurateKappa statistic * 100 Overall model (n=351)72% accurate 66 Water (n=90)100% accurate100 Open grassland (n=56) 92% accurate 91 Hardwood forests (n=67) 61% accurate 53 Chaparral (n=54) 52% accurate 42 Woodland grass (n=84) 48% accurate 37 Tasseled cap model had similar accuracy (K*100)=64 Mixed hardwood forests have highest acarologic risk. Inability of model to accurately characterize this habitat suggests that TM5 imagery may not be sufficiently sensitive for long-term and rapid monitoring of human risk of Lyme disease in northern California Models from Northeast and Midwest with higher accuracy characterized extreme habitats (e.g., forests v. meadows, or wooded lots v. lawns) as opposed to two similar forest types Hyperspectral or higher resolution imagery may be necessary to adequately characterize different forested habitats in region Epidemiological assessment of risk factors Cross-sectional survey of community at high risk for Lyme disease, 14-year follow-up of serological survey and questionnaire conducted in (Lane et al. 1992) 43% cumulative prevalence of Lyme disease, 1.5% annual incidence 11 of 76 variables examined significantly associated with exposure to Lyme disease pathogen, Borrelia burgdorferi (Bb) Length of residence, annual time at residence, time spent outdoors, seasonal use of property, habitat diversity, property management, gardening, caring for animals, ownership of farm animals, stargazing, and lack of protective clothing Activities, behaviors placed residents at high risk for many tick-borne diseases Lyme disease, human granulocytic and monocytic ehrlichiosis, babesiosis, bartonellosis Despite rural environment and behavioral patterns (e.g., time spent outdoors), the majority of risk factors were peri-domestic in nature—similar to Northeast and Midwest Educational efforts conducted 14 years earlier have proved effective Band 4 Woodland GrassOpen GrasslandChaparralWater Hardwood High band variability within each habitat False color TM5 imagery of field sites Habitat-specific reference signatures Landsat TM5 Band 4 v Band 5 comparison showing inability to distinguish any single habitat Band 4 Month These studies were supported by generous grants from NIH and CDC to R.S.L.