MONITORING AND PREDICTING BLACKLEGGED TICK OCCURRENCE IN NORTHWEST NORTH CAROLINA

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Merilyn Johnson
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Harner Department of Biology Appalachian State University

1 MONITORING AND PREDICTING BLACKLEGGED TICK OCCURRENCE IN NORTHWEST NORTH CAROLINA Steven W. Seagle Austin J. Harner Department of Biology Appalachian State University

Blacklegged Ticks and Lyme Disease Lyme is the most common tick-borne disease in North America Caused by the spirochete bacterium Borrelia burgdorferi Vector is the Blacklegged tick (Ixodes

2 Blacklegged Ticks and Lyme Disease Lyme is the most common tick-borne disease in North America Caused by the spirochete bacterium Borrelia burgdorferi Vector is the Blacklegged tick (Ixodes scapularis) Two year life cycle with multiple tick host species The complex life cycle of I. scapularis depends on interactions with: (1) Hosts that utilize the environment at different spatial and temporal scales, and (2) A wide array of habitat, microhabitat, climate, and microclimate conditions. How do we capture this complexity to inform monitoring programs and make predictions about the future occurrence of I. scapularis and Lyme disease?

3 Why Should We Be Interested in N.C.? Most U.S. cases in Northeast and Upper Midwest even though I. scapularis occurs over much of eastern U.S. Much attention to range expansion with climate warming but expanding range in many areas Blacklegged Tick Distribution Red Established; Blue - Reported Over the last decade successive clusters of human cases have expanded southward along the Blue Ridge Mountains Lyme Disease Human Cases Eisen et al J. of Med. Ent. SW VA: Pulaski, Montgomery & Floyd Co. BLT considered established BLT sampled by authors BLT carries Lyme disease bacterium* Cluster of human cases Seukep et al EcoHealth * Herrin et al Vector-Borne And Zoonotic Diseases

Preliminary Blacklegged Tick Sampling In NW North Carolina And SW Virginia Oct 2015 Jan 2016 WV County Park Status TN??? VA NC NC Ashe New River New, Estab.

Mountain Reported Wilkes Stone Mountain New, Report Watauga Elk Knob New, Report VA Floyd (Unknown) Established Grayson Grayson Highlands No Montgomery (Unknown) Established Patrick

4 Preliminary Blacklegged Tick Sampling In NW North Carolina And SW Virginia Oct 2015 Jan 2016 WV County Park Status TN??? VA NC NC Ashe New River New, Estab. Mt Jefferson No Burke South Mountains No Iredell Lake Norman New, Report McDowell Lake James New, Report Rockingham Mayo River New, Report Stokes Hanging Rock Established Surry Pilot Mountain Reported Wilkes Stone Mountain New, Report Watauga Elk Knob New, Report VA Floyd (Unknown) Established Grayson Grayson Highlands No Montgomery (Unknown) Established Patrick Fairy Stone New, Estab. Pulaski Claytor Lake Established Smyth Hungry Mother No Established: 6 individuals, or 2 life stages in a single year Reported: <6 individuals of a single life stage Eisen et al J. of Med. Ent.

5 There are clearly previously unreported locations of Blacklegged ticks in NW North Carolina. How do we prioritize further sampling? LANDSCAPE MODELING GOALS: Apply landscape analysis to guide sampling for local Blacklegged tick populations Explore cluster analysis of climate, elevation & land use variables as correlates of Lyme disease emergence in the Blue Ridge of North Carolina Use local landscape similarity to representative landscapes from disease areas to explore patterns of local emergence and connectivity among local landscapes Landscape Similarity Analysis Using characteristics of a landscape where ticks are known to occur abundantly to predict where else they might occur

METHODS Characterization Of Local Landscapes 1. NC Blue Ridge and VA Blue Ridge and Ridge & Valley were sectioned into 59,358 1 km 2 local landscapes 2.

6 METHODS Characterization Of Local Landscapes 1. NC Blue Ridge and VA Blue Ridge and Ridge & Valley were sectioned into 59,358 1 km 2 local landscapes 2. For all local landscapes: 21 Landscape Variables Methods 30 yr mean Jan Temp (Max, Min, Mean) PRISM 30 yr mean July Temp (Max, Min, Mean) PRISM 30 yr mean Jan, July, Annual Precipitation PRISM Elevation (Mean, SD) USGS Topo Land cover: %Forest, %Ag, %Urban NLCD Fragmentation of Forest by Ag & Urban (Mean, SD) Guido s Toolbox Forest Contagion (Mean, SD) Guido s Toolbox Total Edge Diversity (Mean, SD) Guido s Toobox Ridge & Valley Appalachian Plateau Blue Ridge Piedmont NC VA Coastal Plain

METHODS LOCAL LANDSCAPE CLUSTERING 1. Principal Component Analysis (SAS; Proc Princomp) 2. Cluster Analysis based on the first 10 principal components (SAS; Proc FastClus) 3.

7 METHODS LOCAL LANDSCAPE CLUSTERING 1. Principal Component Analysis (SAS; Proc Princomp) 2. Cluster Analysis based on the first 10 principal components (SAS; Proc FastClus) 3. Mapping of local landscape clusters (ArcGIS) LOCAL LANDSCAPE SIMILARITY ANALYSIS 1. Principal component analysis and cluster analysis for Pulaski, Montgomery & Floyd counties using local landscapes to choose the most representative local landscape 2. Inverse of Euclidean distance (0,1) of other local landscapes from the representative landscape 3. Use three levels of similarity (.9,.85,.8) to create two-phase maps of similarity for local landscapes 4. Apply QRULE to 64x64 km grid of two-phase local landscapes spanning parts of SW VA and NW NC where field sampling will be most intensive 2010 Human Case Distribution From Seukep et al EcoHealth VA NC

RESULTS LOCAL LANDSCAPE CLUSTERING Local Landscape Clusters Mapped On The Blue Ridge And Ridge And Valley Of VA and NC First 10 principal components explain 95% of variation Disjoint cluster analysis

8 RESULTS LOCAL LANDSCAPE CLUSTERING Local Landscape Clusters Mapped On The Blue Ridge And Ridge And Valley Of VA and NC First 10 principal components explain 95% of variation Disjoint cluster analysis was limited to 10 clusters Two cluster types covered approximately 80% of Pulaski, Montgomery, and Floyd counties in VA Local Landscape Clusters Most Common In Pulaski, Floyd, and Montgomery Counties These two clusters also overlap strongly with those portions of the VA Blue Ridge and Ridge & Valley where cluster of human Lyme disease cases occur Human Cases Of Lyme Disease In Virginia

9 RESULTS LOCAL LANDSCAPE SIMILARITY ANALYSIS Similarity >.90 Similarity was measured as the inverse of Euclidean distance between a representative landscape from an area with a cluster of Lyme cases in VA and all other local landscapes Similarity >.85 Similarity is a flexible measure allowing users to consider how stringently similarity is defined Nonetheless, use of a representative landscape appears to lower the spatial extent over which similarity should be applied Similarity >.80

10 RESULTS CREATING A LANDSCAPE OF LANDSCAPES VA Counties Used For Choosing The Representative Landscape And Calculating Similarity Similarity can be used to create a two phase map of likelihood of Lyme disease emergence Each patch in the map is itself a local landscape that can encompass the activities of a wide range of tick host species This map can be analyzed for connectivity and other landscape structural variables just as any habitat or non-habitat landscape representation VA NC New Landscape For Analysis Similarity >.90 Spans VA And NC Border Area Of Concern for Lyme Emergence

6% Largest Cluster Size: 42,400 ha 236,500 ha 318,600 ha Largest

11 RESULTS QRULE ANALYSIS OF LANDSCAPES SIMILARITY >.90 SIMILARITY >.85 SIMILARITY >.80 Percent w/ Similarity: 27.2% 61.1% 78.6% Largest Cluster Size: 42,400 ha 236,500 ha 318,600 ha Largest Cluster Fractal: Total Number Clusters: Percolation: No Yes Yes

12 RESULTS SIMILARITY >.90 ARE PUBLIC LANDS USEFUL FOR MONITORING LYME DISEASE EMERGENCE? Useful: Sufficient: YES NOT CLOSE STATE PARKS NEW RIVER STATE PARK SIMILARITY >.85

13 SUMMARY 1. Blacklegged tick occurrence in northwest North Carolina is widespread. Whether these are new populations resulting from southward movement of ticks, or previsouly undiscovered occurrences is unclear. 2. One well established local population of Blacklegged ticks does occur in northwest North Carolina. Others are likely to occur but sparse sampling has not yet revealed them. 3. Blacklegged tick ecology is inherently a landscape phenomenon because of the wide range of mobility displayed by tick host species. Definition and analysis of Local landscapes is thus a reasonable tool for predicting chance of emergence, planning more specific hypothesis-driven field studies, and developing metapopulation models to examine risk and spread. 4. Cluster analysis and multivariate similarity metrics of local landscape characteristics suggest that the southwest part of Virginia s Ridge and Valley province and the Blue Ridge of North Carolina (especially the northern Blue Ridge) have strong potential for expansion of Blacklegged tick populations. 5. Blacklegged tick habitat and human exposure is not a county-level phenomenon, and cannot be documented by sampling only public lands if the goal is a true accounting of human exposure. 6. Future methods will need to include both researcher initiated, hypothesis-driven field studies, but to fully examine tick distribution, infection rates, and risk other methods, such as citizen science approaches, will need to be implemented.

14 ACKNOWLEDGMENTS UNC Institute for the Environment (Dr. Larry Band) UNC Department of Geography (Dr. Michael Emch) ASU Department of Biology ASU University Research Council North Carolina Department of Environment and Natural Resources Virginia Department of Conservation and Recreation North Carolina Department of Health and Human Services CONTACT INFORMATION Steve Seagle

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