A critical concern in the transmission of prion diseases, including chronic wasting disease (CWD) of cervids, is the potential presence of prions in body fluids. To address this issue directly, we exposed cohorts of CWD-naïve deer to saliva, blood, or urine and feces from CWD-positive deer. We found infectious prions capable of transmitting CWD in saliva (by the oral route) and in blood (by transfusion). The results help to explain the facile transmission of CWD among cervids and prompt caution concerning contact with body fluids in prion infections.

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In this investigation, the nature and distribution of histologic lesions and immunohistochemical staining (IHC) of a proteinase-resistant prion protein were compared in free-ranging mule deer (Odocoileus hemionus) dying of a naturally occurring spongiform encephalopathy (SE) and captive mule deer dying of chronic wasting disease (CWD). Sixteen free-ranging deer with SE, 12 free-ranging deer without SE, and 10 captive deer with CWD were examined at necropsy. Tissue sections were stained with hematoxylin and eosin, and duplicate sections were stained with a monoclonal antibody (F89/160.1.5). Histological lesions in the free-ranging deer with SE and captive deer with CWD were found throughout the brain and spinal cord but were especially prominent in the myelencephalon, diencephalon, and rhinencephalon. The lesions were characterized by spongiform degeneration of gray matter neuropil, intracytoplasmic vacuolation and degeneration of neurons, and astrocytosis. IHC was found throughout the brain and retina of deer with SE and CWD. Positive IHC was found in lymphoid tissue of deer with SE and CWD. Histologic lesions and IHC were not found in multiple sections of integument, digestive, respiratory, cardiovascular, endocrine, musculoskeletal, and urogenital systems of deer with SE or CWD. Comparison of histologic lesions and IHC in tissues of free-ranging deer with those of captive deer provides strong evidence that these two diseases are indistinguishable morphologically.

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ABSTRACT:Effective measures for controlling chronic wasting disease (CWD), a contagious prion disease of cervids, remain elusive. We review theoretic relationships between predation and hostparasite dynamics and describe a mathematical model to evaluate the potential influence of random removal through harvest or culling and selective predation by wolves (Canis lupus) upon CWD dynamics in deer (Odocoileus spp.) populations. Imposing nonselective mortality representing a 15% annual harvest or cull 51 yr after CWD introduction lowered both deer population size and steady state CWD. Selective (43) mortality at the same 15% predation rate caused a more modest reduction in deer population size accompanied by a relatively rapid decline in CWD prevalence and elimination of the disease from a closed population. The impacts of selective predation on epidemic dynamics were sensitive to assumptions on parameter estimates; however, within expected ranges, the results of selective predation were consistent and robust. We suggest that as CWD distribution and wolf range overlap in the future, wolf predation may suppress disease emergence or limit prevalence.