Chronic Wasting Disease (CWD)

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Introduction to CWD;

Chronic Wasting Disease (CWD) is a fatal neuro-degenerative, transmissible spongiform encephalopathy (TSE) of the family Cervidae (Hamir, et.al., 2006). The family Cervidae includes mule deer, Odocolileus hemionus, white-tailed deer, Odocolileus virginianus, Rocky Mountain elk, Cervus elaphus nelsoni, and moose, Alces alces shirasi, among others (Sigurdon & Aguzzi, 2007). CWD is a prion disease, meaning it is a protein caused infection, that occurs naturally in the deer family (Song & Lawson, 2009). This protein is suspected to be an abnormal isoform (PrPSc) of the naturally occurring host prion protein (PrPC) (Blanchong, et. Al., 2009). Bovine spongiform encephalopathy (BSE), mad cow disease, is a similar prion effecting cattle as CWD affects Cervidae. Although, scientists are not sure of transmission route it is suspected that CWD is transmissible and infectious through direct contact with infected individuals or through environmental contamination (Song & Lawson, 2009). Tests have been performed showing susceptibility of altered mice to oral transmission, mimicking the suspected route of entry, and the incubation appears slower but lasts longer with oral infection (Trifilo, et.al., 2007). The approximate time from the initial infection to death is three years.

History of CWD;

The origin of CWD has yet to be determined (Sigurdson & Aguzzi, 2007). The infection was first noted in 1967 at a captive mule deer research facility. In 1978 pathologists recognized the TSE type brain lesions, also that CWD presented as a prion disease by the neuronal perikaryonic vacuoles, the accumulation of aggregated prion protein and prion infectivity in the brain. In the late 1970s and early 1980s the infection w...

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... to 225SF (Sigurdson & Aguzzi, 2007). Elk expressing codon 132MM and 132ML were seen to be a high percentage of the infected while elk expressing 132LL showed resistance to CWD infection for at least four years. In Wisconsin white-tailed deer showed reduced susceptibility with the expression of codons G966S and Q95H.

Conclusion;

White-tailed deer, along with the rest of the Cervidae family, are facing a possible epidemic. Although the disease has not spread over the entire range CWD is efficiently transmitted between individuals. CWD is to the best of our knowledge 100% fetal and incubation can take a few years allowing for many possible transmissions. There also at this time is no form of vaccine or treatment for infected cervids. Despite efforts being put forth to control CWD, being a free-range family of animals proves control to be extremely difficult.

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