Comparison of conventional, amplification and bio-assay detection methods for a chronic wasting disease inoculum pool

McNulty, Erin; Nalls, Amy V.; Mellentine, Samuel; Hughes, Erin; Pulscher, Laura A.; Hoover, Edward A.; Mathiason, Candace K.

doi:10.1371/journal.pone.0216621

Cited by 42 publications

(50 citation statements)

References 82 publications

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“…The CWD-positive brain homogenate inoculum used in these studies was created by pooling sections of brain from six deer with terminal CWD infection [ 33 ]. This cervid brain pool 6 (CBP6) contained 3.33 × 10 6 50% lethal doses/g as determined by intracranial titration in cervid PrP transgenic mice (Tg(cerPrP)5037) [ 32 , 33 , 41 ]. The CWD-negative brain inoculum was confirmed negative by western blot, RT-QuIC, and mouse bioassay [ 33 ].…”

Section: Methodsmentioning

confidence: 99%

“…Other studies have indicated that the concentration of infectious prions in saliva is near the endpoint of a CWD-positive brain homogenate titrated in cervid PrP-expressing transgenic mice; i.e. 10 −6 [ 32 , 33 ]. One hypothesis that may explain such low dose infectivity would be that prions in saliva are inherently more infectious by mucosal exposure routes.…”

Section: Introductionmentioning

confidence: 99%

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Very low oral exposure to prions of brain or saliva origin can transmit chronic wasting disease

et al. 2020

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The minimum infectious dose required to induce CWD infection in cervids remains unknown, as does whether peripherally shed prions and/or multiple low dose exposures are important factors in CWD transmission. With the goal of better understand CWD infection in nature, we studied oral exposures of deer to very low doses of CWD prions and also examined whether the frequency of exposure or prion source may influence infection and pathogenesis. We orally inoculated white-tailed deer with either single or multiple divided doses of prions of brain or saliva origin and monitored infection by serial longitudinal tissue biopsies spanning over two years. We report that oral exposure to as little as 300 nanograms (ng) of CWD-positive brain or to saliva containing seeding activity equivalent to 300 ng of CWD-positive brain, were sufficient to transmit CWD disease. This was true whether the inoculum was administered as a single bolus or divided as three weekly 100 ng exposures. However, when the 300 ng total dose was apportioned as 10, 30 ng doses delivered over 12 weeks, no infection occurred. While low-dose exposures to prions of brain or saliva origin prolonged the time from inoculation to first detection of infection, once infection was established, we observed no differences in disease pathogenesis. These studies suggest that the CWD minimum infectious dose approximates 100 to 300 ng CWD-positive brain (or saliva equivalent), and that CWD infection appears to conform more with a threshold than a cumulative dose dynamic.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Very low oral exposure to prions of brain or saliva origin can transmit chronic wasting disease

et al. 2020

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“…However, classic diagnostic methods, IHC, ELISA, and WB, failed to detect prion deposition at low concentrations, such as the expected amounts during the early phase of prion replication. By contrast, PMCA and RT‐QuIC successfully detected prion presence even at very low concentrations, undetectable by traditional methods (McNulty et al ., ). Thus, considering their insufficient sensitivity for diagnosis in acute phases, IHC, ELISA, and WB should not be used alone for early, asymptomatic CWD surveillance.…”

Section: Cwd Detectionmentioning

confidence: 97%

“…A comparison of CWD detection methods found that all diagnostic methods (IHC, ELISA, WB, PMCA, and RT-QuIC) can successfully detect CWD infection post-mortem in advanced, terminal phases (McNulty et al, 2019). However, classic diagnostic methods, IHC, ELISA, and WB, failed to detect prion deposition at low concentrations, such as the expected amounts during the early phase of prion replication.…”

Section: Cwd Detectionmentioning

confidence: 99%

The ecology of chronic wasting disease in wildlife

et al. 2019

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Prions are misfolded infectious proteins responsible for a group of fatal neurodegenerative diseases termed transmissible spongiform encephalopathy or prion diseases. Chronic Wasting Disease (CWD) is the prion disease with the highest spillover potential, affecting at least seven Cervidae (deer) species. The zoonotic potential of CWD is inconclusive and cannot be ruled out. A risk of infection for other domestic and wildlife species is also plausible. Here, we review the current status of the knowledge with respect to CWD ecology in wildlife. Our current understanding of the geographic distribution of CWD lacks spatial and temporal detail, does not consider the biogeography of infectious diseases, and is largely biased by sampling based on hunters' cooperation and funding available for each region. Limitations of the methods used for data collection suggest that the extent and prevalence of CWD in wildlife is underestimated. If the zoonotic potential of CWD is confirmed in the short term, as suggested by recent results obtained in experimental animal models, there will be limited accurate epidemiological data to inform public health. Research gaps in CWD prion ecology include the need to identify specific biological characteristics of potential CWD reservoir species that better explain susceptibility to spillover, landscape and climate configurations that are suitable for CWD transmission, and the magnitude of sampling bias in our current understanding of CWD distribution and risk. Addressing these research gaps will help anticipate novel areas and species where CWD spillover is expected, which will inform control strategies. From an ecological perspective, control strategies could include assessing restoration of natural predators of CWD reservoirs, ultrasensitive CWD detection in biotic and abiotic reservoirs, and deer density and landscape modification to reduce CWD spread and prevalence.

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“…Seeded amplification assays such as PMCA and RT-QuIC can reliably and specifically detect prion seeding activity that is several orders of magnitude more sensitive than an animal bioassay (50)(51)(52)(53)(54)(55). The relationship between prion infectivity in animals and in vitro seeding activity is only beginning to be understood (56). Detection of prions in blood with PMCA and RT-QuIC from hosts in the preclinical phase of disease before the reliable detection of infectivity in experimental and naturally occurring prion disease is well documented (19)(20)(21)(57)(58)(59)(60)(61)(62) and raises the possibility that this in vitro seeding activity represents bona fide infectious prion particles.…”

Section: Discussionmentioning

confidence: 99%

Failure To Detect Prion Infectivity in Ticks following Prion-Infected Blood Meal

Shikiya

Kincaid

Bartz

et al. 2020

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Chronic wasting disease (CWD) is an emerging and fatal contagious prion disease that affects cervids, including mule deer, white-tailed deer, black-tailed deer, red deer reindeer, elk, and moose. CWD prions are widely distributed throughout the bodies of CWD-infected animals and are found in the nervous system, lymphoid tissues, muscle, blood, urine, feces, and antler velvet. The mechanism of CWD transmission in natural settings is unknown. Potential mechanisms of transmission include horizontal, maternal, or environmental routes. Due to the presence of prions in the blood of CWD-infected animals, the potential exists for invertebrates that feed on mammalian blood to contribute to the transmission of CWD. The geographic range of the Rocky Mountain Wood tick, Dermancentor andersoni, overlaps with CWD throughout the northwest United States and southwest Canada, raising the possibility that D. andersoni parasitization of cervids may be involved in CWD transmission. We investigated this possibility by examining the blood meal of D. andersoni that fed upon prion-infected hamsters for the presence of prion infectivity by animal bioassay. None of the hamsters inoculated with a D. andersoni blood meal that had been ingested from prion-infected hamsters developed clinical signs of prion disease or had evidence for a subclinical prion infection. Overall, the data do not demonstrate a role for D. andersoni in the transmission of prion disease. IMPORTANCE Chronic wasting disease (CWD) is an emerging prion disease that affects cervids, including mule deer, white-tailed deer, black-tailed deer, red deer reindeer, elk, and moose. The mechanism of CWD transmission in unknown. Due to the presence of prions in the blood of CWD-infected animals, it is possible for invertebrates that feed on cervid blood to contribute to the transmission of CWD. We examined the blood meal of D. andersoni, a tick with a similar geographic range as cervids, that fed upon prion-infected hamsters for the presence of prion infectivity by animal bioassay. None of the D. andersoni blood meals that had been ingested from prion-infected hamsters yielded evidence of prion infection. Overall, the data do not support a role of D. andersoni in the transmission of prion disease.

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Comparison of conventional, amplification and bio-assay detection methods for a chronic wasting disease inoculum pool

Cited by 42 publications

References 82 publications

Very low oral exposure to prions of brain or saliva origin can transmit chronic wasting disease

Very low oral exposure to prions of brain or saliva origin can transmit chronic wasting disease

The ecology of chronic wasting disease in wildlife

Failure To Detect Prion Infectivity in Ticks following Prion-Infected Blood Meal

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