Detection of Chronic Wasting Disease Prions in Salivary, Urinary, and Intestinal Tissues of Deer: Potential Mechanisms of Prion Shedding and Transmission

Abstract

Efficient horizontal transmission is a signature trait of chronic wasting disease (CWD) in cervids.Infectious prions shed into excreta appear to play a key role in this facile transmission, as has been demonstrated by bioassays of cervid and transgenic species and serial protein misfolding cyclic amplification (sPMCA). However, the source(s) of infectious prions in these body fluids has yet to be identified. In the present study, we analyzed tissues proximate to saliva, urine, and fecal production by sPMCA in an attempt to elucidate this unique aspect of CWD pathogenesis. Oropharyngeal, urogenital, and gastrointestinal tissues along with blood and obex from CWD-exposed cervids (comprising 27 animals and >350 individual samples) were analyzed and scored based on the apparent relative CWD burden. PrP CWDgenerating activity was detected in a range of tissues and was highest in the salivary gland, urinary bladder, and distal intestinal tract. In the same assays, blood from the same animals and unseeded normal brain homogenate controls (n ‫؍‬ 116 of 117) remained negative. The PrP-converting activity in peripheral tissues varied from 10 ؊11 -to 10 0 -fold of that found in brain of the same animal. Deer with highest levels of PrP CWD amplification in the brain had higher and more widely disseminated prion amplification in excretory tissues. Interestingly, PrP CWD was not demonstrable in these excretory tissues by conventional Western blotting, suggesting a low prion burden or the presence of protease-sensitive infectious prions destroyed by harsh proteolytic treatments. These findings offer unique insights into the transmission of CWD in particular and prion infection and trafficking overall.

Influence of the geographic distribution of prion protein gene sequence variation on patterns of chronic wasting disease spread in white-tailed deer (Odocoileus virginianus)

“…CWD was first detected in cervids in the late 1960s in Colorado [2,3] and has since spread to an increasing number of other US states and Canadian provinces [4,5]. The disease is transmitted horizontally by contact with pathogenic prions shed in bodily fluids [6,7] and vertically from mother to offspring [8,9]. Once shed, prions have been shown to persist in the environment, potentially remaining infectious and furthering disease spread long after affected deer have dispersed [10–12].…”

Longitudinal Detection of Prion Shedding in Saliva and Urine by Chronic Wasting Disease-Infected Deer by Real-Time Quaking-Induced Conversion

“…A leading hypothesis for the facile spread of CWD in wild populations is that the accumulation and excretion of CWD prions in bodily fluids facilitate both direct animal-to-animal transfer and substantial environmental contamination leading to indirect infection (8)(9)(10). Infectious CWD prions have been identified in urine, saliva, blood, and feces by bioassay of deer or cervid PrP Cexpressing transgenic mice (11)(12)(13)(14)(15)(16). Prions bound to soil are remarkably stable, retaining infectivity even after a decade (9,(17)(18)(19)(20).…”

Assessing the Susceptibility of Transgenic Mice Overexpressing Deer Prion Protein to Bovine Spongiform Encephalopathy

“…Consequently, since its initial identification in northern Colorado and southeastern Wyoming, the disease has spread inexorably among North American states and provinces (3). To minimize the incidence of and ultimately to eliminate CWD, extensive surveillance and research projects have been developed (4,5). The ability to study the biology of CWD prions has been enhanced by the development of transgenic mice which overexpress cervid PrP on a mouse null PrP background (6)(7)(8).…”