Chronic Wasting Disease in Alberta: the challenges in management

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1 Chronic Wasting Disease in Alberta: the challenges in management Evelyn Merrill Department of Biological Sciences OFAH Conference 16 March 2019

2 History and Distribution Detection in North America: Captive MD in CO (1967) & WY (1979) Free ranging deer, elk & moose in 1980s in CO & WY Now in 25 states & 2 provinces SK & AB Korea: imported CWD-infected elk in 2000 Most Recent development: CWD in Europe March 2016: S. Norway 19 free ranging reindeer, 1 red deer, 3 moose in N. Norway

3 First Detections Next Door First case in Canada: 1974: mule deer the Toronto Zoo imported from the Denver Zoo Saskatchewan: next door 1996: found in game farms reportable disease to CFIA 2000: found in free-ranging MD 2018: cervids tested >600 deer, >15 elk, 1 moose; 3 foci Voluntary head submission passive voluntary Geist et al. 2017

4 Alberta First Detections & Actions in Alberta 1996: started surveillance in wild No cervid imports Feeding already banned Passive surveillance Response to CWD deer in SK, 241 wild deer sampled along SK/AB border in April 2001: no CWD+ November 2002, CWD in a farmed white-tailed deer in Alberta. Federal CWD eradication: animals tested & killed including those moved off premises in the previous 3 years. Sampled in vicinity: 320 deer and elk all negative for CWD. No other detected cases in area through 2018

5 Canadian Context Chronic Wasting Disease In Canadian Wildlife: An Expert Opinion On The Epidemiology And Risks to Wild Deer Aggressive regional management & research Once establish eradication & control difficult Prevention of new foci high priority - stop transport animals & infectious material - reduce environmental contamination <1 animal/km 2 complete removal in local areas ~10yrs Public education of CWD

6 First Detections & Actions in Alberta Canada s Expert Panel eradicating sparks (new infections) thru depopulation and intense monitoring. Deer control measures: increased hunting opportunities direct control measures in WMUs 150, 151, 234 Disease surveillance in WMUs Mandatory head submission: 151,234,256,500 Voluntary submission: 144,148,152,162,200,202,203,232,236,238

7 CWD Marching Across Alberta! Alberta 2005: first CWD+ in wild passive voluntary mandatory : >80,000 heads tested CWD+ 992 deer, 1 moose, 2 elk Equal sampling ~ 86% mule deer Prevalence 2-3x males > females

8 Proactive partnerships Local cooperation and involvement: Compilation of local knowledge & volunteer efforts Landowners access for trapping & tracking Establishing funding consortium Networking with CWD research

9 Periodic Reviews of CWD Program Internal review: 2008, 2012, 2019 External review Miller et al. 2008

10 Field Research for CWD in Alberta Evolution of our research : local field information on deer in North border area Effects of early management: herd reductions any effect? Risk assessment: based on spatial patterns in CWD+ locations Field information: inputs for modeling CWD : Modeling disease to investigate mechanisms : Initiation & failure of experimental harvest program 2018: Detailed contact studies: Future harvest impacts?

11 Early Herd Reductions in Alberta National Assessment 2004: 1/km 2 Deer reduction was politically charged stopped >3yrs removed >5-6x infected Northern Border Herd reductions: Politically terminated despite effectiveness What did we learn from the reductions?

12 Herd Reductions: What did we learn? National Assessment 2004: 1/km 2 AF&W surveys Spatial distribution: Winter aerial Ribstone surveys by AF&W: Battle river Deer density km 2 Reductions No Reductions Metiskow Dillberry Northern Border Herd reductions: Herds remained low for 2+ years (Merrill et al. 2013)

13 Herd reductions: What did we learn? Reductions No reductions Female mule deer: No change in CWD? Reductions No reductions 5 WMU: Mule deer only Male mule deer: Increase in maybe at same rates Lesson learned: treatments too short? others have found effects (Merrill et al. 2013)

14 What other harvests: Illinois vs. Wisconsin Illinois & Wisconsin: CWD magt same time in 2003 CWD prevalence in Illinois and Wisconsin Manjerovic et al. (2014)

15 Risk of CWD: Species specific deer behaviors 86% CWD positive cases consistent since 2005

16 Deer Density Mule deer White-tailed deer Mule deer White-tailed deer (km 2 ) Study area: P = 0.04 Present only: P = 0.15 Merrill et al. 2013

17 Deer Movement & Habitat Use Migration: Equal migration ~25%, same directions WTD migrate farther than MD Home ranges: No species differences in winter/summer Sex differences in summer 2x Males (11.2 km 2 ) > females (5.6km 2 ) Percent < >15 km < >15 km <5km >15km <5km >15km Mule deer Mule deer White-tailed deer White-tailed deer 4.00 Terrain ruggedness Woody cover Terrain ruggedness P = P = 0.01 Proportion woody cover Mule MD Deer species White-tailed WTD 0.0 Mule MD Deer species White-tailed WTD

18 Deer Group Sizes Winter Aerial Surveys Group size Mule deer White-tailed deer P<0.01 Mule Deer White-tailed Deer Mule deer > group sizes than white-tailed deer not due to detection during sampling or density Habib et al. 2013, Merrill et al. 2013

19 Risk of CWD: Genetic relatedness? Sampling: tissue from hunters (n=2535) across AB & SK in FST/(1 FST); CWD tested Broad-scale: low-moderate genetic differentiation no spatial discontinuities So no broad scale barriers to spread Cullingham et al. 2011

20 Risk of CWD: Genetic relatedness? females males Non-infected CWD-infected P = 0.01 Distance between samples (km) Pairwise- relatedness categories Local-scale: strong autocorrelation in relatedness females > males attributed to rose petal of social groupings more related matched pairs higher probability CWD infection Cullingham et al. 2011

21 Risk of CWD: surveillance patterns in CWD Predictions predictions Update with models Predicted risk: compare harvested CWD + vs CWD - Year: Deer species and sex Habitat: agric/woody/grassl; ruggedness; streams Connectivity to known sources of CWD+ Nobert et al. 2016

22 Modeling questions: Population Modeling What are major transmission mechanisms producing >2x CWD in males? What is the optimal harvest (lowest CWD) under those mechanisms? Potapov et al. 2013, 2016

23 Population Modeling Plausible transmission mechanisms: several one? - Males more susceptible but at least 3-4x females - Contact in social groups combined with rut F M but with segregation into bachelor groups - Environmental transmission if males eat more food and spend time in segregated bachelor groups Optimal harvest: depended on mechanisms, but consistent patterns (1) some removal of females to maintain herd productivity infusion of healthy deer (2) removal of males because high CWD prevalence (3) high removal of infected animals most effective strategy Potapov et al. (2013, 2016)

24 Interactions: Contact collars with GPS Direct contacts Indirect-place-based Hurdle models: (Cross et al. 2012) Individual; specific dyad (pairs): relatedness? Same or different sex groups Landscape connectivity Density & habitat covariates Network path models (Williams et al. 2016) Force of Infection:( t,k,l ) =Σ Prevalence( t,k,l )*Contact_rate( k,j )* T Evaluate management: harvest or vaccine programs effects

25 Adaptive harvest experiments in the face of CWD learning by doing

26 Management Experiment Harvest strategies: selective removals to slow the spread of CWD in Alberta Two replicates in N & S ~ 4 townships Treatments: Males : highest prevalence - more susceptible? - spreading among female and bachelor groups Social groups around CWD+ - spatial structure in deer reflects sociality - density & landscape influence grouping

27 Challenges. Stakeholder agreement Landowners: past legacies & practicalities ABF&W: funding and workload Experimental design how large an area? achieve harvests & for how long? Long-term goal with political /social will to continue Adaptive management: uncertainty lead to inaction

28 Recent Management Initiatives Western Prairie Ecosystems Alberta Montana Colorado Wyoming Saskatchewan

29 Considerations Goal: many different jurisdictions repeat management scenarios so learn collectively Standards for consistency: Duration & size of treatment Level of CWD starting Monitoring frequency Needed associated data for interpretation Social groups around CWD+ 3 Priority treatments Harvest males

30 Reduce Artificial Points of Host Concentrations Hypothesis: Reduce deer visitation to artificial concentration to reduce environmental contamination and transmission. Work with landowners/producers Harvest males Test extent & types of removals to prevent transmission e.g., grain bins; artificial feeders or feeding stations, mineral bins

31 Harvest Management Segment hypothesis: Harvest on the segment most likely to be CWD+ to reduce transmission. Timing hypothesis: Harvest post rut when male are more likely to be CWD+ Harvest males to reduce sooner after infection during rut Remove >30% male bucks post rut CWD+ Hunting regulations to reduce CWD

32 Questions