Chapter 20 Hazard Model 2.0

20.1 What is the Hazard Model 2.0?

The Hazard Model 2.0 incorporates many possible risk factors for chronic wasting disease (CWD) introduction and exposure of wild cervids to proportionately distribute an overall sampling point quota to sub-administrative areas.

20.2 What Questions Does the Model Answer?

Question 1. How can I identify areas with the highest risk of CWD introduction or increasing prevalence to maximize our surveillance efficiency? Cumulative risk scores incorporating identified risks are calculated for each sub-administrative area. Risk scores are an indication of the risk for CWD introduction or increasing prevalence associated with a sub-administrative area; the higher the number, the higher the risk.

The following risk factors may be used to calculate risk in the Hazard Model 2.0: - Natural cervid movement - Dispersing free-ranging cervids - Natural congregation - Mineral licks - Water bodies - Seasonal migration - Artificial congregation - Feedgrounds - Guzzlers or water tanks - Baiting stations - Agricultural practices - Business activities - Captive cervid facilities (e.g., cervid farms and hunting enclosures) - Taxidermists - Meat processors - Wild cervid rehabilitation centers - Carcass rendering facilities - Incineration facilities - Venison food banks - Individual human actions - Landfill disposal of imported carcasses - Carcasses dumped into the environment - Shed antler collection - Roadkill collection - Local practices - Baseline spatial risk - Adjacency to sub-administrative areas in which CWD has been detected

Question 2. How do I distribute sampling effort across my jurisdiction to target areas where CWD is most likely to appear or increase in prevalence? The administrative area-wide sampling point quota, as provided by the user, is distributed proportionately per sub-administrative area based on the risk scores. You assign the appropriate surveillance category to each sub-administrative area according to CWD status and other risk factors. You choose the level of sampling (i.e., number of points) and the model proportionately distributes samples.

Question 3. How do surveillance points convert to the number of cervids my team needs to sample? Surveillance points per sub-administrative area can be used by agencies to determine their surveillance plans. Points, rather than counts, may be used to focus sampling efforts on sex and age classes in which CWD is most likely to be detected. You can select your own risk weights in the Annual Surveillance Collection to guide your surveillance efforts.

Note: The Hazard Model 2.0 does not produce surveillance targets based on statistical confidence. If you wish to determine sample sizes to reach statistical assurance that CWD is absent in an area, use the Sample Size Quotas Using Clustering Model or the Efficient Sample Size Calculator.

Note: The Hazard Model 2.0 does not consider cost. If you wish to determine sample sizes to minimize cost, use the Sample Allocation Model.

20.3 Output Details

Comparative maps, data charts, and tables of the following outputs by sub-administrative area may be viewed on the Visualization page. In addition, the model execution page allows you to download your tabular outputs as .csv or .json files.

  • Baseline Spatial Risk Score: risk arising from spatial proximity to the nearest known CWD infection
  • Total Risk score: risk arising from landscape and herd features
  • Total Hazard Score: obtained by folding the baseline and total risk scores together

20.4 Abbreviated Tutorial

For best results, enter all possible data into the Warehouse:

  1. Enter basic information to identify model run.
  2. Enter parameters, as detailed below.
  3. If desired, create Visualization associated with model run.
  4. If desired, use the model results in an Annual Surveillance Collection entry in combination with a chosen weighting scheme.
  5. Explore the model logs, input file, and output files used in the run.
  6. If the model did not run, check the model logs to understand required data that was missing.

20.5 Parameters Needed to Execute the Model

  • Reference name: Enter a name to help you identify your model run for future reference. Note that this field does not affect the model run.

  • Applicable season year (Optional): Select the season year (for your reference) from the drop-down list. Note that this field does not affect the model run.

  • Notes (Optional): Enter any notes about the model run details. Note that this field does not affect the model run.

Note: To enable the Hazard Model 2.0 to give you the most useful results, it is important to enter as much information as you can.

20.6 Details on the Theory

Thompson N, Sernaker S, Hanley B, Cook J, Hollingshead N, Hubbs A, Reed H, LaHue N, Lieske C, Gillin C, Reeder A, Munk B, Wood L, Justice-Allen A, Duvuvuei O, Crockett E, Wycoff S, DeVivo M, Westacott H, Cook W, Heffelfinger L, Wild M, Epps C, Walsh D, Nelson C, Thacker C, Beckmen K, Schuler K. The Hazard Model 2.0: Extension of a risk-based chronic wasting disease surveillance model to the western United States and Canada. In preparation