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ABSTRACTChronic wasting disease (CWD), a transmissible spongiform encephalopathy of cervids, was first documented nearly 50 years ago in Colorado and Wyoming and has since been detected across North America and the Republic of Korea. The expansion of this disease makes the development of sensitive diagnostic assays and antemortem sampling techniques crucial for the mitigation of its spread; this is especially true in cases of relocation/reintroduction or prevalence studies of large or protected herds, where depopulation may be contraindicated. This study evaluated the sensitivity of the real-time quaking-induced conversion (RT-QuIC) assay of recto-anal mucosa-associated lymphoid tissue (RAMALT) biopsy specimens and nasal brushings collected antemortem. These findings were compared to results of immunohistochemistry (IHC) analysis of ante- and postmortem samples. RAMALT samples were collected from populations of farmed and free-ranging Rocky Mountain elk (Cervus elaphus nelsoni; n= 323), and nasal brush samples were collected from a subpopulation of these animals (n= 205). We hypothesized that the sensitivity of RT-QuIC would be comparable to that of IHC analysis of RAMALT and would correspond to that of IHC analysis of postmortem tissues. We found RAMALT sensitivity (77.3%) to be highly correlative between RT-QuIC and IHC analysis. Sensitivity was lower when testing nasal brushings (34%), though both RAMALT and nasal brush test sensitivities were dependent on both the PRNPgenotype and disease progression determined by the obex score. These data suggest that RT-QuIC, like IHC analysis, is a relatively sensitive assay for detection of CWD prions in RAMALT biopsy specimens and, with further investigation, has potential for large-scale and rapid automated testing of antemortem samples for CWD.

Investigations of chronic wasting disease (CWD), a fatal, contagious prion disease of free-ranging cervids, suggest the disease can cause long-term population declines in deer (Odocoileusspp.). However, the implications of CWD for elk (Cervus elaphus nelsoni) populations are less certain. During 2008–2010, we used rectal biopsies and telemetry to observe disease transmission and survival in adult female elk from a high-density herd in Rocky Mountain National Park (RMNP) that had been infected by CWD for over 25 years. We studied a cohort of 123 adult female elk that were determined to be free of CWD by rectal biopsy in 2008. Annual incidence of CWD was 0.08 [95% Bayesian credible interval (BCI)?=?0.05, 0.12]. Annual survival probabilities of the cohort excluding harvest declined from 0.97 in 2008 (BCI?=?0.93, 0.99) to 0.85 in 2010 (BCI?=?0.75, 0.93). Declines in survival were attributed almost entirely to CWD; the proportion of radiocollared elk that died of CWD increased from 0.02 in 2008 (BCI?=?0.00, 0.05) to 0.11 in 2010 (BCI?=?0.04, 0.21). We attributed the increase to the time lag required for development of new CWD cases. We used survival rates of susceptible and infected elk to develop a projection matrix for a discrete time, female only model that estimated the intrinsic population growth rate (?) of this elk herd to be 1.00 (BCI?=?0.93, 1.05) using the prevalence of CWD (12.9%) and calf:cow ratios (24:100) observed during this study. Population declines were predicted to occur when prevalence of CWD exceeded 13% (BCI?=?0, 35). However, this estimate was contingent on calf:cow ratios and harvest. Greater recruitment will offset some of the effects of CWD, whereas the inclusion of female harvest, which was excluded from this study, would likely result in lower ? values than those observed in this study. We conclude that CWD can exceed natural rates of mortality, reduce survival of adult females, and decrease population growth of elk herds. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.