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. 2009 Jun 16;4(6):e5916.
doi: 10.1371/journal.pone.0005916.

Infectious prions in pre-clinical deer and transmission of chronic wasting disease solely by environmental exposure

Candace K Mathiason  1 , Sheila A Hays, Jenny Powers, Jeanette Hayes-Klug, Julia Langenberg, Sallie J Dahmes, David A Osborn, Karl V Miller, Robert J Warren, Gary L Mason, Edward A Hoover
Affiliations

Infectious prions in pre-clinical deer and transmission of chronic wasting disease solely by environmental exposure

Candace K Mathiason et al. PLoS One. .

Abstract

Key to understanding the epidemiology and pathogenesis of prion diseases, including chronic wasting disease (CWD) of cervids, is determining the mode of transmission from one individual to another. We have previously reported that saliva and blood from CWD-infected deer contain sufficient infectious prions to transmit disease upon passage into naïve deer. Here we again use bioassays in deer to show that blood and saliva of pre-symptomatic deer contain infectious prions capable of infecting naïve deer and that naïve deer exposed only to environmental fomites from the suites of CWD-infected deer acquired CWD infection after a period of 15 months post initial exposure. These results help to further explain the basis for the facile transmission of CWD, highlight the complexities associated with CWD transmission among cervids in their natural environment, emphasize the potential utility of blood-based testing to detect pre-clinical CWD infection, and could augur similar transmission dynamics in other prion infections.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. PrPCWD detection by longitudinal tonsil biopsy and terminal necropsy.
Figure 2
Figure 2. Immunohistochemistry results of deer exposed to body secretions and excreta from CWD+ deer.
PrPCWD demonstrated by immunohistochemistry in tonsil, brain (medulla oblongata at obex), and retropharyngeal lymph node of deer receiving saliva, blood, or environmental exposure from CWD-infected donors. CWD immunohistochemistry is shown in the medulla at obex (a–j) and either tonsil or retropharyngeal lymph node (k–t). Arrows indicate PrPCWD staining (red) within brain and lymphoid follicles. Arrow with * indicates lymphoid follicle negative for PrPCWD.
Figure 3
Figure 3. Western blot results of deer exposed to body secretions and excreta from CWD+ deer.
Western blot demonstration of the typical PK digestion band shift (28–35 kD) associated with prion infection in the brain (medulla oblongata at obex) of deer receiving blood, brain, saliva or environmental exposure, but not urine and feces from CWD-infected donors. Lanes 1–4 represent CWD+/− deer controls (10% brain homogenate of medulla at obex) without and with PK digestion at 25 µg/ml. Lanes 5–12, 10% brain homogenate of blood, brain, urine/feces or saliva inoculated deer without and with PK digestion at 25 µg/ml. Lanes 13–15, brain homogenate from deer environmentally exposed to CWD+ fomites without and with PK digestion at 25 and 50 µg/ml.
Figure 4
Figure 4. Summary of naïve deer exposed to inoculum from CWD+ deer—combined with our previous published findings
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