# 2 new research articles about CWD



## Fierkej (Dec 21, 2001)

Here are the summaries of a couple of new studies on CWD, from Journal of Wildlife Management, July 2002

Chronic wasting disease of deer and elk: A review with recommendations for management
ES Williams, MW Miller, TJ Kreeger, RH Kahn, ET Thorne

Abstract: Chronic wasting disease (CWD) has emerged as an
important disease of wild and farmed cervids in North America. Of the transmissible spongiform encephalopathies (TSEs), or prion diseases, CWD is the only 1 found in free-ranging species. Because the TSEs include infamous diseases like bovine. spongiform encephalopathy (BSE) of cattle and variant Creutzfeldt-Jakob disease of humans, CWD by association has become a disease of interest beyond the parochial concerns where it is found. Consequently, wildlife managers are faced with developing programs for addressing CWD. Mule deer (Odocoileus hemionus), white-tailed deer (O. virginianus), and Rocky Mountain elk (Cervus elaphus nelsoni) are the only species known to be naturally susceptible to CWD. Although implications of CWD are not entirely clear at this time, we know that CWD is a fatal, contagious disease of mature reproductive segments of deer and elk populations. It has been endemic in free-ranging cervids in a core area of contiguous portions of Southeastern Wyoming and northeastern Colorado, USA, for a minimum of 20 years and probably longer. The known geographic distribution of endemic CWD is relatively limited at this time, although as results of intensified surveillance become available, this may change. Foci of CWD in free-ranging deer have been identified distant from the core endemic area as far cast as Wisconsin. Distribution has greatly expanded in the last decade or more via commerce in infected farmed elk; as a result, CWD recently has been found in multiple jurisdictions of the plains, foothills, and Rocky Mountains of western North America, and in South Korea. Studies of the biology and natural history of CWD over the last few years have resulted in a better understanding of its pathogenesis and epidemiology. Chronic wasting disease is transmitted horizontally from infected to Susceptible cervids. Early involvement of alimentary tract-associated lymphoid tissues during incubation suggests plausible routes for transmission via feces or saliva. Residual environmental contamination also appears to be important in sustaining epidemics. Studies of CWD epidemiology led to development of models to help explain the history of CWD as well as forecast its impacts on deer and elk populations. Improved tests allow CWD to be diagnosed early in incubation, long before clinical signs appear. Where CWD is not known to occur, managers should be, and in some cases are, developing surveillance programs and regulations that prevent or reduce the likelihood that CWD will be introduced into their jurisdictions. Where CWD is already endemic, responsible agencies are conducting surveillance to assess status and trends in prevalence and geographic distribution, managing deer and elk populations to limit spread, and developing and evaluating techniques for further controlling and perhaps eradicating CWD. Programs for addressing the challenges of CWD management will require interagency cooperation, commitment of funds and personnel, and applied research. 

Evaluation of antemortem sampling to estimate chronic wasting disease prevalence in free-ranging mule deer
LL Wolfe, MM Conner, TH Baker, VJ Dreitz, KP Burnham, ES Williams, NT Hobbs, MW Miller

Abstract: We conducted it field study to evaluate tonsillar biopsy immunohistochemistry (IHC) as it tool For diagnosing chronic wasting disease (CWD) in live, free-ranging mule deer (Odocoileus hemionus) arid estimating CWD prevalence. Initially, we evaluated arid refined techniques for collecting tonsillar biopsies front mule deer. Using a simple mouth gag arid a 6-mm biopsy, forceps, and taking the biopsy starting at the rostral rim of the tonsillar sinus, we obtained 155/161 (96%) samples that yielded greater than or equal to1 lymphoid follicle. To Compare antemortem arid postmortem survey techniques arid assure biopsy-based estimates would not substantially underestimate "true" prevalence, we examined tonsillar biopsies front 161 free-ranging mule deer from 2 populations where CWD is endemic. We then calculated prevalence (p(b)) and compared this to prevalence (p(h)) estimated from tonsil samples from 161 (feel, hill-vested or culled in spatial arid temporal proximity to our study areas; we considered the latter a close approximation of "true" prevalence. Biopsy-based prevalence estimates exceeded prevalence estimated by tonsillar IHC of samples from harvested or culled deer. Although 95% CIs for p(h) - p(b), included 0 for area-specific estimates, biopsy- based estimates were greater than or equal to3 times higher than harvest-based estimates ill both study areas. Moreover. when data front both study areas were combined, p(h) (= 0.025) was lower than p(b) (= 0.081) and the 95% CI for p(h) - p(b) (-0.104 to -0.007) did not include 0. Observed differences in prevalence most likely reflected spatial or temporal variation in populations (or subpopulations) of deer sampled. Tonsillar biopsy IHC, appears to be reliable for detecting CWD infections in live mule deer and estimating prevalence in affected populations, thereby representing it new tool with potential utility in CWD management, particularly it) areas where harvest-based sampling is infeasible.


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