It has been shown for different prion diseases that PRNP gene heterozygosity can reduce susceptibility and lengthen the incubation period, consequently it appears that as individuals and at the population level canine species like wolf and coyote may have a double genetic advantage (number of PrP variants and the preservation of variants with low conversion efficiency) over bear and puma with regard to overall CWD susceptibility. This evidence concerns the gene PRNP and prion disease.