Susceptibility to chronic wasting disease (CWD) in cervid species has been associated with polymorphisms in the prion protein gene (PRNP). The single nucleotide polymorphisms (SNPs) were found in the PRNP of the Korean subspecies of Chinese water deer via analyses of the DNA sequences obtained from 34 individual deer. Two SNPs were detected at codons 77 and 100. One SNP at codon 77 encoding Glycine was determined to be a silent mutation but the other SNP detected at codon 100 induced an amino acid change, from Asparagine to Serine. The prion protein (PrP) amino acid sequence of the water deer showed 98.8-99.2% homology with those of American elk, white-tailed deer and mule deer. The PrP of the water deer contained amino acid residues closely related with CWD-susceptibility. This study is the first to describe genetic variations in the PRNP of the Korean subspecies of Chinese water deer.

To determine the suitability and estimate the sensitivity of an immunohistochemical (IHC) test for disease-associated prion protein (PrP(Sc)) in biopsy specimens of rectoanal mucosa-associated lymphoid tissue (RAMALT) for diagnosis of scrapie in sheep. 762 sheep at high risk for having scrapie and indemnified by the National Scrapie Eradication Program. The IHC test for PrP(Sc) was applied to 2 RAMALT and 2 third-eyelid biopsy specimens and a postmortem RAMALT specimen from each sheep. Results were compared with those of a reference test in which results for tissues from obex and retropharyngeal lymph nodes, tonsil, or both were considered in parallel. The reference test identified 139 sheep as having scrapie. Biopsy-related complications occurred in 3 sheep. Sensitivity of the IHC test in RAMALT ranged from 85.3% to 89.4%, depending on the anatomic location from which RAMALT was obtained. Results for the test applied to 1 RAMALT specimen were similar to results interpreted in parallel for 2 third-eyelid specimens (sensitivity, 87.0%). The proportion of inconclusive test results attributable to insufficient lymphoid follicles in biopsy specimens was lower when considering results for 2 RAMALT specimens in parallel (10.1%) than when considering results for 2 third-eyelid specimens in parallel (23.7%). Specimens of RAMALT that were inappropriately collected from an area caudal to the rectoanal interface yielded a high proportion of inconclusive results (33.3% to 50.0%). The IHC test for PrP(Sc) in RAMALT was an effective means of detecting subclinical scrapie in live, high-risk sheep.