SAC/2017/03/02 SCOTTISH NATURAL HERITAGE SCIENTIFIC ADVISORY COMMITTEE PAPER. Chronic Wasting Disease in Deer

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1 SCOTTISH NATURAL HERITAGE SCIENTIFIC ADVISORY COMMITTEE PAPER Chronic Wasting Disease in Deer Summary 1. Chronic Wasting Disease in deer has been reported for the first time in Europe. The European Food Standards Agency has recently published its opinion and DEFRA has updated the qualitative risk assessments. This paper summarises the current understanding of CWD and the risk it possess to deer in the UK, considers some wider implications. Action 2. The Committee is asked to advise on: whether all entry routes have been acknowledged, if mitigation is a feasible option, and the possibility of further restrictions on animal movements being advocated; and wider consequences for the natural heritage. Preparation of Paper 3. This paper was prepared by Alastair MacGugan with input from Claudia Rowse and Colin Shedden. It is sponsored by Andrew Bachell. Background 4. Chronic wasting disease (CWD) is a highly contagious and deadly animal brain disease. It belongs to a group of diseases known as Transmissible Spongiform Encephalopathies (TSE). CWD only affects deer. Up to 2016, it was reported only in North America and South Korea where it has had devastating effects on many populations of wild and farmed deer. In March 2016, Norway became the first European country to report cases of CWD in wild deer as well as the first ever case in wild reindeer. 5. CWD was first identified as a clinical disease of captive mule deer in Colorado in 1967 and later classified as a TSE in The origin of the disease is unknown and may have been a spontaneous TSE that arose in deer. Currently, natural infections of CWD have been reported in the USA and Canada in mule deer (Odocoileus hemionus hemionus), black-tailed deer (Odocoileus hemionus columbianus), white-tailed deer (Odocoileus virginianus), Rocky Mountain elk (Cervus elphus nelsoni), Shira s moose (Alces alces shirasi) and mule deer and white-tailed deer hybrids. It has also been reported in elk in South Korea, but this has been traced directly to elk imported from Canada. 6. The widespread distribution in the USA and two Canadian provinces may have been detected due to enhanced surveillance or may have been due to an increase in natural movements of cervids and translocation of infected animals by humans. In Wyoming the prevalence of CWD in mule deer has increased from approximately 11% in 1997 to 36% 1

2 in In such areas, population declines of deer of up to 30 to 50% have been observed. In areas of Colorado, the prevalence can be as high as 30% In summary what is known about CWD 2 is: It is fatal for infected cervids; The prions (infectious agent composed entirely of protein material) causing CWD transmit easily amongst cervids, either directly or indirectly in the environment; The prions associated with CWD are present throughout the brain tissue, lymphatic system and peripheral organs and are an abnormal form of the prion protein (PrP). They are also shed via saliva, faeces and urine, and bind strongly to soil and remain infectious in the soil for many years; Plants can absorb prions from the soil and may subsequently infect through digestion (this has so far only been shown in laboratory conditions with mice fed infected plant material); Cattle and sheep are at a very low risk of developing CWD and current evidence implies that prion diseases in sheep and cattle are unlikely to be the origin of CWD; Sporadic or genetically originated occurrences of prion disease in cervids cannot be ruled out. Genetic variation in the gene that encodes for PrP can modulate sensitivity to CWD resulting in incubation periods of 1.5 to 3 years; The extent of genetic variation of the gene encoding for PrP is currently unknown for deer in Scotland; Through laboratory inoculation experiments red and roe deer are susceptible to CWD with fallow deer being less so; Differing strains of CWD have been found and may have an influence on transmission rates. Diagnosis based on clinical signs is not reliable, because they are unspecific and mild at the beginning of the disease. Currently, it depends on detecting the abnormal prion in the central nervous system. The current most common method for analysis is therefore post mortem and via tissue samples from the obex (small triangular membrane at the caudal end of the roof of the fourth ventricle of the brain); The zoonotic (transmission to humans) potential for CWD is considered to be negligible.. Reported European cases 8. There has been only limited TSE testing of wild cervids in Europe. A survey carried out across Europe during found no positive results. An EFSA opinion in 2010 concluded that there was not a cervid TSE epidemic in the EU In mid-march 2016 a sick reindeer in the Nordfjella area of Norway was observed and subsequently died. It was confirmed by the CWD Reference Laboratory in Canada to be consistent with CWD in Canadian wild cervids and with reindeer experimentally 1 From DEFRA 2016 What is the risk of a cervid TSE being introduced from Norway into Great Britain? Qualitative Risk Assessment 2 See VKM (2016) CWD in Norway. Opinion of the Panel on Biological hazards, ISBN , Oslo, Norway; EFSA (2017) Chronic wasting Disease: addressing risks for the EU, EFSA Journal 2017;15(1): EFSA BIOHAZ Panel 2010, Scientific Opinion on the results of the EU survey for Chronic Wasting Disease (CWD) in Cervids EFSA Journal 2010;8(10):1861 2

3 inoculated with CWD. This was the first worldwide reported case of CWD in free ranging reindeer. 10. In May 2016, again in Norway, a young adult, pregnant, female moose was confirmed as having CWD. The moose had shown abnormal behaviour and was in poor body condition. The moose came from a different area (Selbu municipality in Sør-Trøndelag, close to the Swedish border) than the CWD case in reindeer. A third case was confirmed from a young pregnant female moose from the same Selbu area. 11. A freak lightning strike killed ca 300 reindeer in the Nordfjella area and all 300 were tested and came up negative for CWD. Norway then implemented an intensive sampling regime which screened for CWD in wild deer from this year s hunting season, with 6000 animals tested from all over the country, including 2000 red deer. This brought the total of confirmed cases to 5. The two additional cases were both from the Nordfjella reindeer herd; a 7 year old male and 4 year old female. Both were reported as in apparently good health. 12. As of the end of December 2016 a further 824 additional animals which died in accidents or were found dead were screened, with no positives found. Further screening of the semi-domesticated reindeer was also undertaken and as of mid- January 2017 no positives for CWD were found. This would imply that prevalence in the wild population is extremely low at around %, is restricted to a small geographical area and that neither red deer nor roe deer have been confirmed infected. Response to reported case a) EU and Norway 13. Quickly after the reporting of CWD, Norway imposed a ban on the movement of live cervids which was further backed up by the Commission Implementing Decision (EU) 2016/1918. There are a number of exemptions to this ban which are related to the seasonal movement of herded reindeer across the Norwegian/Finnish/Swedish borders. There are also some exemptions to the live movement for slaughter between the three countries. These exemptions are aimed at providing a proportionate and practical response in terms of the herded reindeer populations of the Sami people. 14. Norway will continue with its surveillance programme through the 2017 hunting season and from carcasses found, particularly from vehicle collisions. Infected deer in N. America have been found to be more susceptible to vehicle collisions than uninfected deer. The EFSA Opinion described below (paragraph 18) proposes a three-year monitoring system across eight countries (Norway, Sweden, Finland, Iceland, Estonia, Latvia, Poland and Lithuania) to detect if the disease is present. b) UK 15. In the UK the SG Deputy Chief Vet set up a CWD Technical Group. This group includes SG vets, DEFRA vets, APHA and other representatives from the UK TSE Group. It also includes SNH, BASC Scotland, BDS and The Deer Initiative. It was primarily formed to advise on the review of the DEFRA Quantitative Risk Assessments following the first two Norwegian CWD cases. As the Norwegian reports developed the group has prepared and issued advice on CWD particularly aimed at hunters and walkers who may be visiting high risk areas. The group has also taken an overview of some of the 3

4 responses in North America to limit the spread and intensity of CWD. On the back of this overview discussions have started on outline contingency planning. 16. DEFRA reviewed its Qualitative Risk Assessment on the risk of cervid TSE coming into the UK in March In September 2016 DEFRA developed a further more specific Qualitative Risk Assessment on the risk of cervid TSE coming into the UK from Norway. In summary the current risk is assessed as :.. the probability of importing a TSE into the GB deer herds from Norway and causing infection in British deer is uncertain but likely to be no greater than very low via movement of deer hunters, other tourists and British service personnel; at most, low via live animal imports or imported (non-ruminant) animal feed; very low for the use of lures specifically sourced in Norway and negligible for plant imports. However, if it was imported and (a) deer did become infected with CWD, the consequences would be severe as eradication of the disease is unfeasible, it is clinically indistinguishable from BSE infection in deer and populations of wild and farmed deer would be under threat The review of the risk assessments highlighted the additional specific risk from the importation of reindeer from Norway into the UK primarily to service a demand for Santa Grottos and other Christmas public exhibitions. This trade had been raised as an issue previously but in response to a growing concern over the subsequent treatment of the animals post their use in Christmas displays. The previous imports into the UK have mainly been through the semi-domesticated reindeer in the north of Norway and are thus separated from the infected population of reindeer in Nordfjella. 18. The EU Commission asked EFSA for an opinion on the CWD cases reported in Norway and what a proportionate response would be. This EFSA Opinion was published in January Overall, the opinion highlighted the lack of knowledge around CWD. The opinion recommended the surveillance program for the seven countries described above, questioned the movement of live cervids and provided a list of measures that could be put in place if assuming CWD was already present. A decision by DEFRA as to whether a UK surveillance program should be implemented is awaited. Transmission rates 19. It has proven difficult to model the advancement of CWD in part due to poor understanding of the transmission routes and rates. Infected prions are found in placenta, skin (including antler), milk, faeces, urine, saliva, soil (probably in descending order of infectivity). In addition material from carcases most notably the central nervous system and the gastro-intestinal tract should be considered highly infectious. Although saliva and urine would appear to be of a relatively lower infectivity they are important routes because of the repeated exposure to them. This is especially important where dealing with higher deer densities and when supplementary feeding or a mineral lick is provided. 20. One major determining factor in susceptibility appears to be genetic variation within the prion protein gene (PRNP). In North American cervids, four PRNP sequence variants have been associated with prolonged survival of CWD-infected animals, but genotyping of the major UK deer species is limited. Work has just started, led by the Roslin Institute, 4 DEFRA 2016 What is the risk of a cervid TSE being introduced from Norway into Great Britain? Qualitative Risk Assessment 4

5 to perform a survey of PRNP genetics in red, roe and sika deer, using existing sample collections. In addition the work will also look at the correlation between the identified sequence variants and the efficiency by which PrP can be induced to misfold. 21. This assessment of susceptibility when combined with knowledge of deer populations will be useful to model the spread and potential impact of CWD in the UK. There are still challenges in ensuring that the population information is adequate. Especially in relation to deer movements and deer in the lowlands. Entry routes 22. The origins of CWD remain a mystery. Possible explanations include the spontaneous conversion of normal prion protein (PrP) into an abnormal form (PrP Sc ) which is then transmissible and/or infection from an as yet unrecognised prion. This lack of understanding makes it difficult to ascertain whether there is any link between the Norwegian and North American CWD cases. It may be that CWD has existed undetected in European for some considerable time. 23. The DEFRA risk assessments identify likely routes of infection. Prevention and Mitigation 24. The only way to rapidly inactivate the infectious agent of CWD is to soak articles in a solution of bleach that has 20,000 parts per million of active chlorine, or 2 molar sodium hydroxide solution for one hour. This treatment would obviously be highly detrimental to most clothing, footwear and hunting equipment and so is mostly impractical. Through the CWD Technical Group, and funded in part by SNH, a promotional leaflet was 5

6 produced for circulation at Scone Game Fair and subsequently to the major sporting agents. The advice being advocated was: a) As a countryside user visiting the UK/USA/Canada Consider whether you need to take clothing/equipment with you. Clothing and equipment bought or borrowed, used and then left in North America poses no risk to UK deer populations. If you need to bring such clothing or equipment to the UK, make sure it is scrupulously clean of all potential contamination - soil, blood, faeces etc. Meticulous cleaning of all adherent debris from equipment and clothing, especially footwear, will significantly reduce the risk of introducing CWD into this country, although it will not eliminate the risk. Do not bring any trophies or body parts back to the UK. b) As a host/sporting agent Send this leaflet to North American stalking guests and also those who may have visited North America so they are aware of their responsibilities. Check all of their kit for cleanliness (it is unlikely that their kit will have been inspected for appropriate cleanliness at border control). Don t assume that because they are visiting from North America they will be aware of the risk of CWD transmission. 25. The use of deer urine lures has been implicated in the spread of CWD in North America. A ban on the use of natural urine lures has been implemented across the EU. This ban does require further promotion within hunting and nature photography circles. a) Action in North America 26. In North America, attempts to control the spread of CWD have included the banning of supplementary feeding or nutrient licks, ban on the movement of cervids between certain states, and a wide publicity campaign. In a number of states targeted culling has been implemented to either eradicate CWD from commercial game farms or to reduce the wild cervid density. It is to be noted that in a number of states, game farms with relatively high densities of cervids are prolific and caution is therefore needed when comparing with the UK situation. Notwithstanding the above it is estimated that the costs to the individual state natural resource management departments associated with the management for CWD ranged from $5m to $30m annually. b) UK contingency planning 27. Within the UK, contingency planning is being considered. As a first step SNH has been asked by the CWD Technical Group to undertake a desk exercise to consider the scale and effort required to put in place a control cull in an open hill red deer and then low ground roe deer scenarios. Any contingency planning would require a controlled cull to be backed up with other measures such as a ban on the movement of any cervid into 6

7 the area, control over the disposal of deer by-products (including DVC casualties), the control over the sale and processing of venison and statutory testing of all carcasses. 28. Currently there is no outright ban on the movement of live cervids within the EU. Nor is there a ban on the movement of ovum. This may be reviewed in light of the EFSA Opinion and any decision on further surveillance proposals. The Deer Farming and Deer Parks sectors would advocate that with the lack of evidence of CWD outwith Norway any such restrictions would be costly and not proportionate. Public health 29. Although CWD has been present in hunted populations of cervids for at least 30 years, no case of human CWD has been identified. Importantly there has been no association made between occurrences of CJD in humans and exposure to CWD. There is, however, no evidence of an absolute species barrier between CWD affected cervids. Wider implications for the natural heritage 30. We need to give consideration to the potential impacts of CWD on national and regional deer populations, and implications on the sporting sectors, tourism and natural heritage interests. 31. From a nature conservation perspective we would need to consider the consequences of major losses of grazing, browsing and trampling especially in woodland and upland landscapes. We also need to consider the risks of major regional losses of deer, and any bearing of this on genetic integrity (though noting that population susceptibility would be highly varied). We have already put in place measures to have the Outer Hebrides designated as red deer refugia in order to conserve red deer populations as free from Sika genes (effectively prohibiting introductions of red deer from the mainland through statutory orders). 32. The potential recovery of deer in CWD impacted areas is not well understood, and would at least need to be modelled. 33. One aspect that would require careful investigation is the possibility of infected deer being more prone to colliding with vehicles, for this would have serious implications for road safety. This would apply especially to red and roe deer. 34. Finally, if CWD became established, this would have major implications for how we currently mange red der across DMGs, and red and roe deer in woodlands in and south of the Central Belt. Biosecurity measures would constrain some stalking activities, yet we would swiftly need to put in place containment measures to control CWD outbreaks. 35. The Committee is asked to consider the issues concerning CWD, especially this final section, and to advise on scientific issues we should be actively considering regarding the natural heritage, which we would take to the CWD Technical Group. Alastair MacGugan, alastair.macgugan@snh.gov.uk 7