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Phenotype: Chronic wasting disease is characterized by weight loss, dehydration, behavioral changes, a rough dull coat, and excessive salivation. A natural mutation in the prion protein gene in elk has been found to have a protective effect to CWD. Elk with one copy of the protective variant have a longer incubation time before clinical signs appear. Elk with two copies of the protective variant have the longest incubation time before clinical signs appear.
Alleles: M = Methionine at codon 132, L = Leucine at codon 132 (delays progression of CWD disease)
Species appropriate for testing: Elk
Explanation of Results:
- Elk with M/M genotype have no copies of the protective leucine variant and are susceptible to CWD. This is the most common genotype in wild and farmed elk, with the shortest incubation time.
- Elk with M/L genotype have one copy of the protective leucine variant and are susceptible to CWD. This is the second most common genotype in wild and farmed elk, with an intermediate incubation time.
- Elk with L/L genotype have two copies of the protective leucine variant and are more resistant to CWD. This is the least common genotype in wild and farmed elk, with the longest incubation time.
Chronic wasting disease (CWD) is a fatal transmissible spongiform encephalopathy (TSE) of elk and other cervids in North America. Other TSE diseases include scrapie and bovine spongiform encephalopathy (BSE). CWD is characterized by weight loss, dehydration, behavioral changes, a rough dull coat, and excessive salivation.
CWD infection causes the normal cellular prion protein (PrP) to be converted to an abnormal form. This conversion of PrP initiates the disease process. DNA sequencing of the PrP gene in elk has identified a single base difference at codon 132. This genetic difference among animals changes the amino acid from methionine to leucine, which affects the incubation time of CWD. There is no evidence of true resistance to CWD in elk. Testing of elk for codon 132 of PrP helps breeders of farmed elk to select for animals that are less susceptible to CWD.
Among all farmed elk tested to date for codon 132 by the VGL, 52% were M/M, 40% were M/L and 8% were L/L. We note however that frequencies of these genotypes can vary greatly within herds, depending upon the genetic make-up of each herd and potential selective breeding for the L allele.
