CHRONIC WASTING DISEASE 
CURT NITSCHELM, DVM APRIL 2001

Chronic Wasting Disease is a spongioform brain disease of deer and elk. It was first observed in 1997 at a research pen in Fort Collins Colorado.

Signs:
1.Weight loss
2.Excessive drinking /urinating / salivating
3.Droopy head and ears
4.Depression / no fear of humans
5.Death within weeks to months

Tentative diagnosis:
1.Nutritional
2.Captive stress
3.From 1974 - 1979, 57 out of 67 captive deer died in Wyoming and Colorado of the unknown disease.

Diagnosis:
1.Dr. Beth Williams - veterinary pathologist from Wyoming
2.CWD belonged to a family of diseases known as Transmissible Spongioform Encephalopathies (TSE).
3.Classic vacuoles in the brain tissue on necropsy, Immunohistochemisry.
4.No live animal test available.

Causative agent:
1.Unknown - Suspect a new germ called Prions. Prions are proteins that are found on nerve cell membranes in mammals. Prions also act as a kind of gene, passing valuable traits in studies of yeasts. Prions have many different forms like bacteria and viruses. The absence of prion proteins on nerve cells of mice causes learning disabilities and muscle diseases.
2.Stanley Prusiner - Nobel Prize winner in 1997. He believes there is an infectious prion protein that causes other normal prion proteins to twist and convert to the dangerous infectious prion. The end result is death to the nerve cell causing the classic microscopic holes in the brain.

Transmission: Unknown
1.Infected animal to infected animal
2.Infected premises - pens were plowed, disinfected and vacated for 1 year and 2 out of 12 still contracted CWD within 5 years
3.Probably saliva, urine and/or feces
4.Agent is resistant to normal sterilization procedures, including rendering, burning, autoclaving, formalin and disinfectants.
5.Highest prevalence is around man made enclosures, feeding practices, water tanks, salt licks, etc. Incubation period: 16 month to 4 years / Average 2.5 years

Treatment: None

Prevention:
1.Population reduction in wild endemic areas
2.Eliminate man induced concentration areas, winter feeding practices, hunter education (no salt, etc.)
3.Captive herds - CWD monitoring program, depopulate all positive herds. 4.APHIS and USDA to provide national funding for testing and indemnity to all captive cervids
5.Educate hunters and the public

Morbidity: 5% wild deer and 1% wild elk endemic areas

Mortality: 100%

Distribution (see map):
1.Wild deer and elk ·NE/N Central Colorado Unit 9 Larimer County about 15% Units - 8, 9, 19, 20, 95, 96, 191, 951 ·SE Wyoming Units - 64, 63, 62, 60, 59, 16 ·SW Nebraska - 1 deer ·Saskatchewan - First deer this month
2.Captive cervids (14 U.S. herds / 11 depopulated) ·Colorado/Wyoming - research and 1 quarantine county ·Nebraska - 1 quarantine ·Oklahoma - 1 quarantine ·South Dakota - 10 herds depopulated (30% infected) ·Montana - 1 herd depopulated ·Canada (Saskatchewan) - 6 herds (1700 animals) depopulated

Transmission to man or domestic animals:
No known cases. Other species can be infected experimentally by injecting CWD brain matter in to an animal's brain. Researchers in Hamilton, Montana found protein from different species was placed together in test tubes to evaluate conversion rates. Closely related animal species had a greater likelihood of transmission. Deer proteins converted 10 - 15% of elk proteins, but deer affected fewer sheep proteins and even fewer cow and human proteins.

Related TSE diseases
1.Humans 
    A.Infectious 
        1.Kuru - 1959, "Hannibal" laughing disease 
        2.nz Creutzfeldt-Jakob - 100 cases from 1996 to 2001 
        3.Creutzfeldt-Jakob -? 1 case/1 million people 
    B.Inherited 
        1.Fatal Familial Insomnia 
        2.Gerstmann-Staussler Scheinkedis 
        3.Creutzfeldt-Jakob?

2.Cattle - infectious, Bovine Spongioform Encephalopathy(BSE), otherwise known as Mad Cow Disease

3.Sheep - infectious, Scrapie or Mad Sheep Disease

4.Mink - infectious, Transmissible Encephalopathy of Mink

Hunter prevention in endemic areas
1. Do not shoot or eat sick animals
2. Avoid contact with brain, spinal cord, eyes, spleen, thymus, lymph nodes, and bone marrow
3. Use rubber gloves when dressing an animal or removing a cape or antlers.
4. Bone out all the meat and remove lymph nodes.
5. Volunteer brain testing is available in Colorado and Wyoming

Facts and concerns on TSE's/CWD
1.Scrapie (Mad Sheep) - has been around for 300 years with no evidence of it causing CJD or nz CJD in people.
2.Scrapie in rendered feed is suspected to have caused the BSE outbreak (Mad Cow Disease) in Britain in 1985 to 1989
3.BSE - 180,000 cases from 1985 to November 2000
4.Britains exposed to 80 tainted meals from 1985 to 1989
5.100 nz CJD cases in Great Britain with 50 million people exposed to BSE and 1 case nz CJD/500,000 people.
6.CWD - smaller human exposure rate
7.No CWD feed tests in monkeys yet?!!
8.Outdoor Life/Field and Stream found 3 hunters died of CJD in 3 years
9.CJD occurs in 1 out of one million people. U.S. has 200-300 CJD deaths per year.
10.The three deer shot by the 3 men that died form CJD came from non-CWD endemic areas. CDC tested several deer form those areas with no positives
 11.No human form of CJD from hunters in endemic CWD areas.

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