Abstract
Chronic wasting disease (CWD), the only known prion disease endemic in wildlife, is a persistent problem in both wild and captive North American cervid populations. This disease continues to spread and cases are found in new areas each year. Indirect transmission can occur via the environment and is thought to occur by the oral and/or intranasal route. Oral transmission has been experimentally demonstrated and although intranasal transmission has been postulated, it has not been tested in a natural host until recently. Prions have been shown to adsorb strongly to clay particles and upon oral inoculation the prion/clay combination exhibits increased infectivity in rodent models. Deer and elk undoubtedly and chronically inhale dust particles routinely while living in the landscape while foraging and rutting. We therefore hypothesized that dust represents a viable vehicle for intranasal CWD prion exposure. To test this hypothesis, CWD-positive brain homogenate was mixed with montmorillonite clay (Mte), lyophilized, pulverized and inoculated intranasally into white-tailed deer once a week for 6 weeks. Deer were euthanized at 95, 105, 120 and 175 days post final inoculation and tissues examined for CWD-associated prion proteins by immunohistochemistry. Our results demonstrate that CWD can be efficiently transmitted utilizing Mte particles as a prion carrier and intranasal exposure.
Highlights
Chronic wasting disease (CWD) is a naturally occurring transmissible spongiform encephalopathy (TSE) of deer, elk and moose that affects captive as well as wild populations
Chronic wasting disease infection The CWD status of the negative inoculum was verified by protein misfolding amplification (PMCA) and the positive by western blot analysis prior to inoculation
Control brain inoculum remained negative after six 24 hr rounds of PMCA amplification and western blot visualization
Summary
Chronic wasting disease (CWD) is a naturally occurring transmissible spongiform encephalopathy (TSE) of deer, elk and moose that affects captive as well as wild populations. Elk excretion of prion is likely greater as they are much larger animals This ongoing, progressive environmental contamination may be substantial in areas with large cervid populations and a high incidence of CWD. Prions can persist and transmit disease years after removal of infected animals and indirect environmental transmission in deer has been documented [4,9,10]. Feces or saliva have been deposited in the environment on forage and soil, they become available for ingestion and inhalation. In addition to oral ingestion of soil, deer and elk stir up and inhale dust during foraging, running and rutting behaviors such as advertising, territorial, and hierarchical displays [17,18]. We propose that inhalation of CWD-contaminated dust particles during these behaviors is a likely route of exposure
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