The demographic pattern of infection with chronic wasting disease in reindeer at an early epidemic stage

Mysterud, Atle; Madslien, Knut; Viljugrein, Hildegunn; Vikøren, Turid; Andersen, Roy; Güere, Mariella Evelyn; Benestad, Sylvie L.; Hopp, Petter; Strand, Olav; Ytrehus, Bjørnar; Røed, Knut; Rolandsen, Christer Moe; Våge, Jørn

doi:10.1002/ecs2.2931

Cited by 28 publications

(44 citation statements)

References 57 publications

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“…Epidemiological parameters: Demographic infection pattern and relative risk . The relative infection likelihood is defined based on the demographic infection pattern of CWD in reindeer 65 . We used a relative infection likelihood of 1:2:6 for yearlings:adult females:adult males unless otherwise stated.…”

Section: Methodsmentioning

confidence: 99%

Hunting strategies to increase detection of chronic wasting disease in cervids

et al. 2020

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The successful mitigation of emerging wildlife diseases may involve controversial host culling. For livestock, 'preemptive host culling' is an accepted practice involving the removal of herds with known contact to infected populations. When applied to wildlife, this proactive approach comes in conflict with biodiversity conservation goals. Here, we present an alternative approach of 'proactive hunting surveillance' with the aim of early disease detection that simultaneously avoids undesirable population decline by targeting demographic groups with (1) a higher likelihood of being infected and (2) a lower reproductive value. We applied this harvesting principle to populations of reindeer to substantiate freedom of chronic wasting disease (CWD) infection. Proactive hunting surveillance reached 99% probability of freedom from infection (<4 reindeer infected) within 3-5 years, in comparison to~10 years using ordinary harvest surveillance. However, implementation uncertainties linked to social issues appear challenging also with this kind of host culling.

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Section: Methodsmentioning

confidence: 99%

Hunting strategies to increase detection of chronic wasting disease in cervids

et al. 2020

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“…Based on anecdotal evidence, males seem more prone to use wider areas than females; CWD infection was more prevalent among male reindeer in Nordfjella (Mysterud, Madslien, et al, 2019). with dogs in France (Maillard & Fournier, 1995); repeated hunts in the same area within a short period were thought to cause an increased risk of extensive movement by wild boar (Scillitani, Monaco, & Toso, 2010).…”

Section: Organization Of Hunting Containment Efforts and Risk Of Dmentioning

confidence: 99%

The last moves: The effect of hunting and culling on the risk of disease spread from a population of reindeer

Mysterud

Rauset

Moorter

et al. 2020

Journal of Applied Ecology

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1. Hunting and culling are frequently used to combat infectious wildlife diseases. The aim is to markedly lower population density in order to limit disease transmission or to eradicate the host. Massive host culling can yield a trade-off when combating wildlife disease; it follows that intrusive actions may have unintended behavioural side effects, leading to the geographic spread of disease. The manner in which such excessive hunting and culling of hosts can affect the movement and dispersion of cervids has not been studied. 2. In this study, we quantified the behaviour (daily movements and habitat use) and dispersion of GPS-marked reindeer (n = 24) before and during the eradication of an entire population (>2,000 reindeer) infected with chronic wasting disease (CWD) in Norway. We compared behaviour and dispersion during 10 ordinary hunting seasons (2007-2016), an extended hunting season (2017) and marksmen culling (2017/2018). 3. Seasonality had a major impact on movements. Reindeer movements during the early hunting season (20 August-20 September) did not increase the overall movements compared to that in the pre-hunt season (20 July-19 August), while extended hunting into October (as in 2017) and marksmen culling from November to February markedly increased daytime movements relative to that normally observed in this time of the year. Towards the end of the eradication, the remaining reindeer sought refuge at restricted high-elevation areas with limited forage production. Reindeer used novel areas towards the perimeter of the range, but active herding during culling stopped one herd from leaving the CWD zone. 4. Synthesis and applications. With emerging wildlife diseases, host culling is becoming a more frequently used tool for managers in Europe. Our study highlights the potential trade-off between combating disease transmission within a population and the risk of geographic spread. Such insight is important to design mitigation measures, such as perimeter fencing or herding, to avoid the risk of the geographic spread of disease in cases of severe and economically important wildlife diseases. This is an open access article under the terms of the Creat ive Commo ns Attri butio n-NonCo mmerc ial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

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“…In sporadic prion diseases, prions are largely confined to the CNS, while in contagious forms, such as classical scrapie and CWD, prions can be prominently present in peripheral lymphoid organs, including lymph nodes, spleen, and along the gastrointestinal tract 26 . Of the 19 reindeer that tested positive for CWD in Norway, all were positive in their lymphoid tissues 27 , therefore, contagious under natural conditions. Hence, in contrast to the Kuru epidemic among humans that was driven by ritual cannibalism, the transmission of CWD among reindeer in Norway likely involved common transmission mechanisms as experienced in North America.…”

Section: Antler Gnawing: Any Link To Cwd?mentioning

confidence: 99%

“…Contagious CWD with prions in CNS and lymphatic tissue All CWD infected reindeer positive in lymphatic tissue27 …”

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confidence: 99%

Antler cannibalism in reindeer

Mysterud

Ytrehus

Tranulis

et al. 2020

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Prion diseases constitute a class of invariably fatal and degenerative encephalopathies. Chronic Wasting Disease (CWD) is a contagious prion disease among cervids, which is spreading and causing marked population declines in USA and Canada. The first outbreak of CWD in Europe was discovered in a reindeer population in Norway in 2016. In the worst-case scenario with continental-wide spreading of CWD in Eurasia, an annual harvest of around 4 million cervids is at stake only in Europe, with huge economic and cultural significance. An in situ origin of CWD was suspected, and it appear urgent to identify the likely cause to prevent future emergences. Here, we document the novel phenomenon of extensive antler cannibalism prior to shedding among reindeer in the CWD-infected population. The extent of antler cannibalism increased over the last decades when CWD emerged, and included ingestion of vascularized antlers. Ingestion of tissues from conspecifics is a risk factor for the emergence of prion diseases, where the presence of extensive antler cannibalism opens the intriguing possibility of a ‘Kuru-analogue’ origin of CWD among the reindeer in Europe. Based on general insight on pathology of prion diseases and strain selection processes, we propose an hypothesis for how contagious CWD may emerge from sporadic CWD under the unique epidemiological conditions we document here. More research is required to document the presence of prions in reindeer antlers, and whether antler cannibalism actually led to a strain selection process and the emergence of a contagious form of CWD from a sporadic form of CWD.

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The demographic pattern of infection with chronic wasting disease in reindeer at an early epidemic stage

Cited by 28 publications

References 57 publications

Hunting strategies to increase detection of chronic wasting disease in cervids

Hunting strategies to increase detection of chronic wasting disease in cervids

The last moves: The effect of hunting and culling on the risk of disease spread from a population of reindeer

Antler cannibalism in reindeer

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