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Chronic wasting disease (CWD) is a chronic, fatal disease of the central nervous system of mule deer,white-tailed deer, Rocky Mountain elk, and (rarely) moose. Chronic wasting disease belongs to the group of diseases called transmissible spongiform encephalopathies (TSEs). These disorders are thought to be caused by abnormal proteins called “prion proteins.” Prion proteins are neither bacteria nor viruses. They are proteins devoid of nucleic acid, thus they are not living organisms.
Prion proteins have similar amino acid sequences as normal cellular proteins but in a different conformation. The functional role of the normal cellular proteins is unknown. Prion proteins cause a conformational change in the normal cellular protein and disease is induced when the normal cellular protein is converted into the prion protein, which apparently can no longer serve its normal role. This eventually causes brain cells to die. As more and more cells die, the disease can be observed to progress, ultimately ending in death.
The only animals known to get CWD are members of the Cervidae family (deer, elk, moose). Affected animals will have one or more of the below signs:
1. Emaciation, poor body condition, rough hair coat.
2. Behavioral changes (hyperactive when constrained; reluctance to move; ears droop).
3. Excessive salivation (sometimes).
4. Excessive drinking (or staying close to water source).
5. Lethargy (but will react when approached closely).
The mode of transmission of CWD has not been identified. Evidence suggests that CWD can be transmitted from animal to animal or from animal to the environment (soil, water, plants) back to another animal. The prion proteins can probably be shed in saliva, urine, or feces where they can contaminate the environment. The most likely rout of exposure is through ingestion.
There are other transmissible spongiform encephalopathies that tend to be species specific and most are not naturally transmissible between species due to a "species barrier.” Examples include:
1. Scrapie of domestic sheep
2. Bovine spongiform encephalopathy (a.k.a. BSE or "mad cow disease) of cattle and a few domestic cats and zoo ruminants in Great Britain and Europe
3. Transmissible mink encephalopathy of ranched mink.
Humans can also suffer from transmissible spongiform encephalopathies, the most notable include:
1. Creutzfeldt-Jakobdisease (CJD), a sporadic disease found worldwide at about 1 in one millionpopulation
2. New variant CJD, probably caused by the prion protein of BSE or "madcow disease.”
3. Kuru, a nearly extinct disease of the Foretribe of Papau, NewGuinea.