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Understanding Chronic Wasting Disease (CWD): Insights and Implications for Wildlife Management

Chronic Wasting Disease (CWD) is a fatal transmissible spongiform encephalopathy affecting white-tailed deer, mule deer, and elk, caused by self-replicating prion proteins that induce abnormal protein folding. Clinical signs include decreased appetite, body condition decline, and neurological symptoms such as tremors and ataxia, with an incubation period that may span months to years. CWD is spreading into new areas and poses significant threats to wildlife health, wildlife economics, and public health. Surveillance and control measures are crucial as Michigan prepares to protect its cervid populations from this infectious disease.

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Understanding Chronic Wasting Disease (CWD): Insights and Implications for Wildlife Management

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Presentation Transcript

  1. Rose Sydlowski Nicole Sheimo

  2. What is CWD? • Transmissible spongiform encephalopathy • Occurs in white-tail deer, mule deer, and elk • 100% fatal

  3. TSE’s • Prions: “infectious proteins” (probably) • Abnormal form of a normal cell protein found in CNS and lymphoid tissues • Self-replicating: causes conformational change in normal proteins, converting them to prions • Neurodegenerative: spongiform change in cerebrum, neuronal degeneration, accumulation of abnormal protein

  4. Other TSE’s • Scrapie: 1st reported mid-1700’s, never found in other species • BSE: 1st case probably occurred 1985, only TSE known to affect both humans and animals • CJD: human TSE, vCJD = human “mad cow” • Transmissible mink encephalopathy

  5. Clinical Signs of CWD • Adult animal • Decreased appetite • Poor body condition • Tremors, stumbling, ataxia • Difficulty swallowing • Increased thirst, PU • Excessive salivation, drooling • Incubation: months to years • Signs persist days to months (up to 1 yr)

  6. Transmission • Not fully understood, may be lateral transmission: • urine, feces, saliva • Increased population density • Captivity (contact with wild) • Feeding • VERY resistant in environment

  7. Diagnosis • Histopathology Spongiform lesions in brain • Immunohistochemistry detects CWD protein in brain and lymphoid tissue

  8. Diagnosis • IHC: parasympatheticnucleus in obex

  9. Diagnosis • IHC on brainstem neurons: • CWD protein stains darkly • Vacuolization of neurons

  10. CWD has been known to exist • since 1967– • mule deer in Colorado • Small endemic area recognized • in wild herds: • Northeast Colorado • Southeast Wyoming • Southwest Nebraska Why do we care about it now??

  11. IT’S EPI TIME!!! • CWD is spreading: • New areas of CO and NE • Has since been found (wild or captive) in SD, KS, OK, MT, MN, NM, and…. • WISCONSIN!! (White-tail, 2002)

  12. EPI TIME • Prevalence • Wild herds: limited data • < 1-15% mule deer • < 1% elk • Captive herds: higher prevalence • 23-90%, depending on herd

  13. Control • Challenging: • No treatment • No vaccine • Long incubation period • No reliable antemortem test • Persistent in environment • Transmission = ?

  14. Control • Captive herds: • Depopulate or quarantine • Environmental contamination? • Wild herds: • Surveillance • Containment, eradicate? • Limit movement of animals • Ban supplemental feeding • Population reduction (?)

  15. What about Michigan? • Discovery of CWD in Wisconsin threat to Michigan! • Goal: Keep CWD out!!! • 1.8 million wild deer and elk • 900-1000 privately-owned facilities (~25000 animals)

  16. What about Michigan? • If introduced into MI, CWD would negatively impact: • Animal health: wild and captive • Economics: • Quarantines and restrictions on MI cervids • Public health fears-- hunting

  17. Michigan’s Plan • Importation of cervids: Banned • Supplemental feeding: Banned in UP (and LP) • Increased surveillance • Education: Hunters, Farmers, Residents • Response Plan: plans for containment and eradication

  18. Surveillance • MI was conducting surveillance before CWD found in WI: • 1998: DNR tested 459 deer from NE LP, all (-) • “Targeted” surveillance: tested deer with suspicious symptoms, all (-)

  19. Surveillance • DNR and MDA: New plans include “targeted” and “active” testing • ~6000 wild deer over the next 3 years • ~50 deer per county • ~50 elk per year • Additional testing of captive cervids

  20. Surveillance • IHC testing of tissues will be performed by the Diagnostic Center for Population and Animal Health

  21. Transmissible– to people?

  22. Suggestions for Hunters • No evidence that people can contract CWD by eating infected animals • CDC: risk is “extremely small, if it exists at all” • In CWD areas: very low % of animals are infected

  23. Suggestions for Hunters • Don’t consume meat from infected or ill animals • Don’t consume nervous system or lymphatic tissues; minimize contact • Wear gloves when field dressing, wash hands • Bone out meat • Have head tested

  24. References CWD Alliance: www.cwd-info.org Michigan DNR: www.michigan.gov/dnr Minnesota DNR: www.dnr.state.mn.us/mammals/deer/cwd.html Dr. Matti Kiupel And special thanks to our model, Kevin Kristick!

  25. Questions?

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