Mineral licks as environmental reservoirs of chronic wasting disease prions.

Ian H Plummer,Chad J Johnson,Michael D Samuel,Joel A Pedersen,Alexandra R Chesney,Anthony E Kincaid

doi:10.1371/journal.pone.0196745

Abstract

Chronic wasting disease (CWD) is a fatal neurodegenerative disease of deer, elk, moose, and reindeer (cervids) caused by misfolded prion proteins. The disease has been reported across North America and recently discovered in northern Europe. Transmission of CWD in wild cervid populations can occur through environmental routes, but limited ability to detect prions in environmental samples has prevented the identification of potential transmission “hot spots”. We establish widespread CWD prion contamination of mineral licks used by free-ranging cervids in an enzootic area in Wisconsin, USA. We show mineral licks can serve as reservoirs of CWD prions and thus facilitate disease transmission. Furthermore, mineral licks attract livestock and other wildlife that also obtain mineral nutrients via soil and water consumption. Exposure to CWD prions at mineral licks provides potential for cross-species transmission to wildlife, domestic animals, and humans. Managing deer use of mineral licks warrants further consideration to help control outbreaks of CWD.

Highlights

Chronic wasting disease (CWD) was first observed in 1967 [1] and long thought to be a disease of minor scientific curiosity affecting mule deer (Odocoileus hemionus) and confined to the Rocky Mountains in northern Colorado and southern Wyoming, USA
The generally higher detection frequency of CWD prions in water samples relative to the corresponding soil samples suggests that either prion concentrations are higher in the water samples or that coextracted constituents from soil inhibited amplification by mb-PMCA
Saliva from white-tailed deer infected with CWD contains on the order of 1–5 infectious doses (ID50) per 10 mL as quantified by real-time quaking-induced conversion, where an ID50 is the dose of CWD prions capable of infecting half of the transgenic mice expressing cervid prion protein [48]

Summary

Introduction

Chronic wasting disease (CWD) was first observed in 1967 [1] and long thought to be a disease of minor scientific curiosity affecting mule deer (Odocoileus hemionus) and confined to the Rocky Mountains in northern Colorado and southern Wyoming, USA. The disease was found in white-tailed deer (O. virginianus) and elk (Cervus canadensis). The geographic range of CWD has expanded dramatically since 2000 [2] and is present in 25 U.S states, two Canadian provinces (http://www.nwhc.usgs.gov/disease_information/ chronic_wasting_disease/index.jsp), South Korea, Norway [3], and Finland (https://yle.fi/ uutiset/osasto/news/first_case_in_finland_elk_dies_due_to_chronic_wasting_disease/ 10108115) and has been found in moose (Alces alces) and reindeer (Rangifer tarandus) [2,4]. CWD prevalence has continued to increase with some free-ranging herds.

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