Could avian scavengers translocate infectious prions to disease-free areas initiating new foci of chronic wasting disease?

Fischer, Justin W.; Phillips, Gregory E.; Nichols, Tracy A.; VerCauteren, Kurt C.

doi:10.4161/pri.25621

Cited by 8 publications

(11 citation statements)

References 31 publications

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“…This has been suggested for scats of coyotes ( Canis latrans ), raccoons ( Procyon lotor ) (Hamir et al ., ; Moore et al ., ), and crows ( Corvus spp.) (Fischer et al ., ), but has not been tested empirically. Scats may also be of potential utility in CWD surveillance and early detection, as predators can selectively predate CWD‐infected cervids (Nichols et al ., ).…”

Section: Strategies To Control the Spread Of Cwdmentioning

confidence: 99%

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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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Section: Strategies To Control the Spread Of Cwdmentioning

confidence: 99%

“…coyotes) and scavengers (e.g. crows and raccoons) exist that could act as vectors of the infectious prion (Bunk, 2004;Fischer et al, 2013;Moore et al, 2019). Similarly, while fawns are known to be susceptible, little is known of their role in the shedding and spread of CWD.…”

Section: Chronic Wasting Disease Biology Epidemiology and Tranmentioning

confidence: 99%

The ecology of chronic wasting disease in wildlife

et al. 2019

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“…Despite long‐standing interest about how scavengers might reduce infectious disease transmission (e.g. vultures; Beasley et al, , Bellan, Turnbull, Beyer, & Getz, , Fischer et al, ), and many studies on individual disease systems (Houston & Cooper, ; Hugh‐Jones & DeVos, ; Ogada, Torchin, Kinnaird, & Ezenwa, ), there is no consensus on whether scavengers generally reduce infections from carcasses or spread pathogens throughout the environment and thus increase transmission (Van Allen et al, ; Beasley et al, ). This is in large measure because of the observational nature of the previous studies and focus on the potential for transmission (but see Bellan et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Despite long-standing interest about how scavengers might reduce infectious disease transmission (e.g. vultures; Beasley et al, 2015, Bellan, Turnbull, Beyer, & Getz, 2013, Fischer et al, 2013, and many studies on individual disease systems (Houston & Cooper, 1975;Hugh-Jones & DeVos, 2002;Ogada, Torchin, Kinnaird, & Ezenwa, F I G U R E 2 The proportion (± 95% C.I.) of nine naïve salamander larvae that became infected with a ranavirus after 24 hr of exposure to an infectious salamander carcass.…”

Section: Discussionmentioning

confidence: 99%

“…while grazing), and thus transmission (Houston & Cooper, 1975;Hugh-Jones & DeVos, 2002;VerCauteren, Pilon, Nash, Phillips, & Fischer, 2012). For example, scavenging birds and mammals appear to spread infectious prions from a carcass, which is essentially a point-source, to much larger areas (Fischer, Phillips, Nichols, & VerCauteren, 2013;VerCauteren et al, 2012). Thus, there are good reasons to think that scavengers as a functional group play an important role in population-level disease dynamics.…”

Section: Scavengersmentioning

confidence: 99%

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Do scavengers prevent or promote disease transmission? The effect of invertebrate scavenging on Ranavirus transmission

2019

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Host–parasite interactions are shaped by the broader web of community interactions, from interspecific competition to predator–prey dynamics. Heterospecific scavengers might also affect parasite transmission from infectious carcasses, which can be an important source of infections for some wildlife diseases. A robust scavenger community can quickly remove carcasses and tissue and thus prevent secondary transmission by necrophagy or contact with infectious carcasses. Alternatively, by spreading infectious particles and tissues throughout the environment, scavengers may increase rates of casual contact with pathogens and thus overall transmission. However, there has been little empirical consideration of the contrasting roles that scavengers might play in infectious disease dynamics. We carried out a series of studies to determine the efficiency with which scavenging invertebrates remove carcasses of Long‐toed Salamander (Ambystoma macrodactylum) larvae and their role in the transmission of frog virus 3 (Genus: Ranavirus, Family: Iridoviridae) from carcasses. We then estimated the functional response of one efficient invertebrate scavenger (Family: Dytiscidae) to increasing carcass densities in field conditions in order to determine the capacity of scavenging invertebrates to consume large amounts of carcass tissue, as may be present at high prevalence sites. We found that removal of infectious carcasses by scavengers strongly reduced transmission to naïve larvae. Scavengers were as effective at reducing transmission from a carcass as a physical barrier preventing contact with the carcass. There was little evidence that scavenging released sufficient infectious tissues into the water column to rival direct contact as a route of infection. Moreover, while scavenging rates saturated at increasing carcass densities, consistent with a type II functional response, there were sufficient densities of dytiscid larvae, not to mention other scavenging invertebrates, in a surveyed pond to theoretically prevent transmission from carcasses. Our results suggest that at least in systems in which conspecific necrophagy is common, the scavenger community can play an important role in reducing transmission. A plain language summary is available for this article.

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Scavengers reduce potential brucellosis transmission risk in the Greater Yellowstone Ecosystem

Szcodronski

Cross

2021

Ecosphere

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Scavengers likely play an important role in ecosystem energy flow as well as disease transmission, but whether they facilitate or reduce disease transmission is often unknown. In the Greater Yellowstone Ecosystem, scavengers are likely to reduce the transmission and subsequent spread of brucellosis within and between livestock and elk by consuming infectious abortion materials, thereby removing the infectious agent from the landscape. We used remote cameras to monitor the time to removal of simulated abortion materials by scavengers at 264 sites from February to June in 2017 and 2018 and assessed the effects of habitat and land management on time to removal in southwest Montana. Time to removal of fetal materials decreased in grassland habitats (x = 2.9 d, credible interval = [1.8-5.0]) in comparison to sagebrush habitats (x = 5.4 d [3.4-9.3]) and forest habitats (x = 5.2 d [3.3-9.0]). In addition, there was an 88% probability that time to removal of fetal materials was slower at sites where mammalian scavengers were actively reduced (x = 6.5 d [3.4-12.8]) compared to sites with no scavenger reduction (x = 4.1 d [2.3-7.8]). Our research indicates that if elk and livestock are commingling during the brucellosis risk period, there is a 90% probability that abortion materials will be removed by scavengers within 16 d across all sites. Coyotes, red foxes, golden and bald eagles, Corvus spp., and turkey vultures were the dominant scavengers, removing 90% of the fetal materials. Actions to maintain the breadth and diversity of scavengers on the landscape are potential management options that could reduce disease transmission risk to livestock in a system where the wildlife reservoir is difficult to address.

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Could avian scavengers translocate infectious prions to disease-free areas initiating new foci of chronic wasting disease?

Cited by 8 publications

References 31 publications

The ecology of chronic wasting disease in wildlife

The ecology of chronic wasting disease in wildlife

Do scavengers prevent or promote disease transmission? The effect of invertebrate scavenging on Ranavirus transmission

Scavengers reduce potential brucellosis transmission risk in the Greater Yellowstone Ecosystem

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