PrP genotypes of free-ranging wapiti (Cervus elaphus nelsoni) with chronic wasting disease.

Variation in PrP prion gene sequence appears to modulate susceptibility to chronic wasting disease (CWD), a naturally occurring prion disease affecting four North American species of the family Cervidae. Wapiti (Cervus elaphus nelsoni) PrP is polymorphic at codon 132 [methionine (M) or leucine (L)]. We genotyped 171 samples, collected between 2002 and 2005 from CWD-infected and uninfected wapiti from three free-ranging populations in Colorado, USA, to study influences of PrP polymorphisms on CWD susceptibility further. Overall genotype frequencies for 124 apparently uninfected animals were 65.3 % MM132, 32.3 % ML132 and 2.4 % LL132; for 47 CWD-infected animals, these frequencies were 70.2 % MM132, 27.7 % ML132 and 2.1 % LL132. Surprisingly, our data revealed that, among recent (approx. 2002--2005) CWD cases detected in free-ranging Colorado wapiti, the three PrP codon 132 genotypes were represented in proportion to their abundance in sampled populations (P> or =0.24) and all three genotypes showed equivalent susceptibility to infection.