Thursday, June 19, 2025

Risk assessment on the likelihood of spread of chronic wasting disease to Great Britain from Scandinavia and North America in November 2023 (executive summary)

 Research and analysis

Risk assessment: chronic wasting disease to Great Britain from Scandinavia and North America
A qualitative risk assessment on the likelihood of chronic wasting disease incursion into Great Britain from Scandinavia and North America, and the potential for subsequent transmission among susceptible animal populations.
Details This risk assessment provides a qualitative assessment of the risk of susceptible species in Great Britain becoming infected with chronic wasting disease (CWD) prions from affected regions of Scandinavia and North America through various legal movement of animals, their commodities as well as people.
The annual likelihood of entry associated with these pathways was considered very low with low to high uncertainty.
The annual likelihood of exposure ranged from negligible to very low with low to high uncertainty, depending on the specific pathway and deer population considered (wild, farmed, or park deer).
The potential consequences of a CWD incursion, given the possible animal welfare, trade, social, and economic effects, were considered major with medium uncertainty.
Research and analysis
Risk assessment on the likelihood of spread of chronic wasting disease to Great Britain from Scandinavia and North America in November 2023 (executive summary)
Published 18 June 2025
This summary outlines a qualitative risk assessment which has been completed to assess the risk of deer species in Great Britain becoming infected with chronic wasting disease (CWD) through legal trade from Scandinavia and North America. This considers the legal movement of animals, animal products and people. The risk is assessed as of November 2023.
Please note this is the executive summary only. To request the full risk assessment, please contact ukassurance@defra.gov.uk  
The annual likelihood that a CWD prion will enter Great Britain through legal trade was considered very low (event is very rare but cannot be excluded) with medium uncertainty.
The annual likelihood of a susceptible animal being exposed to these prions ranged from negligible (event is so rare that it does not merit consideration) to very low with low to high uncertainty, depending upon the specific pathway and deer population considered (wild, farmed, or park deer).
The potential national consequences of a CWD incursion, given the possible animal welfare, trade, social, and economic effects, were considered major with medium uncertainty.   
This is the fifth update of a risk assessment dating from 2012, which originally investigated the risk of incursion of CWD in Great Britain from the USA and Canada. The assessment was updated in March 2016 to include a new import pathway, cervid urine lures. In September 2016, a new update followed the report of CWD-like disease in wild reindeer in Norway, with 2 new entry pathways added (plants, trees and shrubs with root balls, and non-cervid animals, including working dogs). The risk assessment was further updated, in June 2017 and May 2018, following the identification of additional CWD cases among wild reindeer, moose, and red deer in Norway, and the first report of CWD in a wild moose in Finland, respectively. The fifth, most recent, update was finalised in November 2023. 
Background 
Since the last update in May 2018, CWD has continued to spread throughout captive and free-ranging cervid populations in North America. At the time of the last update, it had been found among captive or free-ranging cervids in 24 US states and 2 Canadian provinces, but as of November 2023, this had risen to 32 US states and 4 Canadian provinces.  
In addition, further cases have been identified in 3 wild reindeer, 10 moose and 2 red deer in Norway and 2 wild moose in Finland. The disease has also been reported for the first time in Sweden, with 4 cases identified in the wild moose population there between 2019 and 2020. 
Chronic wasting disease can be broadly classified as classical (C-CWD) or atypical (A-CWD). The main distinction is the distribution of prions in the lymphoreticular system (LRS), particularly the lymph nodes and spleen. 
It is hypothesised that A-CWD may be associated with reduced (or absent) prion shedding, which may not be high enough to sustain natural transmission. However, there is high uncertainty around this, due to limited research. Therefore, A-CWD was considered still within this risk assessment alongside C-CWD.   
The following pathways were considered as part of the entry assessment:  
live cervids 
working dogs 
scavenging birds 
cervid meat 
trophy items 
hides, skins and leathers 
urine lures 
cervid manure 
equipment, clothing or footwear 
plants, trees and shrubs 
hay and straw 
animal feed 
cervid germplasm 
ticks 
Hazard 
Any CWD prion strain in Scandinavian and North American cervids. 
Risk questions 
1) What is the annual likelihood of CWD prions from affected regions of Scandinavia and North America entering Great Britain?    
2) What is the annual likelihood of a cervid within Great Britain being exposed to and infected with CWD prions? 
3) What are the potential consequences of a CWD incursion into Great Britain?   
Main findings 
Entry pathways 
Cervid meat, plants, shrubs and trees and animal feed were all considered to have a very low likelihood of importing CWD, with medium uncertainty.  
There was high uncertainty surrounding the likelihood of entry associated with hay and straw, cervid trophy items, working dogs and equipment. As the uncertainty was so high, an accurate estimation of the risk was not possible. Therefore, these were considered non-negligible (high uncertainty). ‘Non-negligible’ does not necessarily mean a high risk of entry, but indicates that while the risk is greater than negligible (so rare it does not merit consideration), it is not possible to give a more exact risk estimate.  
Scavenging birds, cervid urine lures, manure, live cervids, germplasm and ticks were all considered negligible risk (medium uncertainty). The risk estimated in this update was based on levels of trade with North America and Scandinavia as of November 2023, including trade restrictions such as the suspension of live deer imports and urine lures.    
Exposure pathways 
The annual likelihood of a susceptible animal in Great Britain being exposed to these prions was highest for hay and straw with a very low likelihood (high uncertainty). If a susceptible cervid in Great Britain was exposed to prions, then the likelihood of this causing a clinical case of CWD was considered high (occurs very often) with medium uncertainty.  
Consequence assessment 
A CWD incursion into Great Britain could have substantial animal health and welfare impacts in deer, including significant population declines, as have been seen in the USA. In turn, there could be significant disruption of rural tourism, sporting and farming operations in affected areas, as well as significant job losses and land contamination with CWD prions. Prions are challenging to control once introduced into an area, particularly if present in the wild animal population. The disease control costs involved in eradication are likely to be significant, requiring extensive testing and culling. The degree of trade restrictions on cervids and cervid products such as fresh meat are hard to quantify. Therefore, the potential consequences of a CWD incursion, given the possible animal welfare, trade, social, and economic effects, were considered major (major impact for small population, systems significantly compromised and abnormal operation, if at all, high level of monitoring required) with medium uncertainty.   
Key uncertainties 
Entry assessment 
The key uncertainties in entry assessment are:  
the number of working dogs, such as hunting dogs, imported from North America or Scandinavia
the quantity of cervid meat imported by travellers in luggage or vehicles from Norway, Finland, and Sweden
frequency of movements between Great Britain and the CWD-affected areas of North America and Scandinavia by hunters, overseas and British tourists, and British service personnel, as well as the level of environmental contamination in these areas
the efficacy of deer-proofing measures in growing areas for plants, trees and shrubs within Scandinavia and North America
the ability of plant species other than grasses to bind, uptake, and transport CWD prions and the degree to which this may contribute towards CWD transmission under field conditions
the ability of CWD prions to contaminate, survive, and transmit from hay and straw and the proportion of hay and straw imports which originate from CWD-affected areas of North America
Exposure assessment
The key uncertainties in exposure assessment are as follows: 
differences in shedding and transmission between A-CWD and C-CWD
potential exposure of wild and park deer in Great Britain to CWD prions through various sources, including contaminated soil, vegetation, animal feed and cervid meat
the transfer of CWD prions via contaminated clothing and equipment
the frequency of soil consumption among deer
the minimum infectious dose 
the susceptibility of British cervid species to different CWD strains
Consequence assessment 
The key uncertainty is consequence assessment is: 
unknown trade restrictions due to an outbreak in Great Britain
whether eradication or containment would be attempted
CWD Risk Assessments
Monday, April 17, 2023
EFSA Monitoring of chronic wasting disease (CWD) (IV)
Saturday, April 9, 2022
EFSA EU Request for a scientific opinion on the monitoring of Chronic Wasting Disease (CWD) EFSA-Q-2022-00114 M-2022-00040 Singeltary Submission
''The association between venison eating and risk of CJD shows similar pattern, with regular venison eating associated with a 9 FOLD INCREASE IN RISK OF CJD (p = 0.04).''
CREUTZFELDT JAKOB DISEASE SURVEILLANCE IN THE UNITED KINGDOM THIRD ANNUAL REPORT AUGUST 1994
Consumption of venison and veal was much less widespread among both cases and controls. For both of these meats there was evidence of a trend with increasing frequency of consumption being associated with increasing risk of CJD. (not nvCJD, but sporadic CJD...tss) These associations were largely unchanged when attention was restricted to pairs with data obtained from relatives. ...
Table 9 presents the results of an analysis of these data.
There is STRONG evidence of an association between ‘’regular’’ veal eating and risk of CJD (p = .0.01).
Individuals reported to eat veal on average at least once a year appear to be at 13 TIMES THE RISK of individuals who have never eaten veal.
There is, however, a very wide confidence interval around this estimate. There is no strong evidence that eating veal less than once per year is associated with increased risk of CJD (p = 0.51).
The association between venison eating and risk of CJD shows similar pattern, with regular venison eating associated with a 9 FOLD INCREASE IN RISK OF CJD (p = 0.04).
There is some evidence that risk of CJD INCREASES WITH INCREASING FREQUENCY OF LAMB EATING (p = 0.02).
The evidence for such an association between beef eating and CJD is weaker (p = 0.14). When only controls for whom a relative was interviewed are included, this evidence becomes a little STRONGER (p = 0.08).
snip...
It was found that when veal was included in the model with another exposure, the association between veal and CJD remained statistically significant (p = < 0.05 for all exposures), while the other exposures ceased to be statistically significant (p = > 0.05).
snip...
In conclusion, an analysis of dietary histories revealed statistical associations between various meats/animal products and INCREASED RISK OF CJD. When some account was taken of possible confounding, the association between VEAL EATING AND RISK OF CJD EMERGED AS THE STRONGEST OF THESE ASSOCIATIONS STATISTICALLY. ...
snip...
In the study in the USA, a range of foodstuffs were associated with an increased risk of CJD, including liver consumption which was associated with an apparent SIX-FOLD INCREASE IN THE RISK OF CJD. By comparing the data from 3 studies in relation to this particular dietary factor, the risk of liver consumption became non-significant with an odds ratio of 1.2 (PERSONAL COMMUNICATION, PROFESSOR A. HOFMAN. ERASMUS UNIVERSITY, ROTTERDAM). (???...TSS)
snip...see full report ;
Stephen Dealler is a consultant medical microbiologist deal@airtime.co.uk
BSE Inquiry Steve Dealler
Management In Confidence
BSE: Private Submission of Bovine Brain Dealler
snip...
DEER SPONGIFORM ENCEPHALOPATHY SURVEY
3. This will be a low key study with no publicity to avoid unnecessary media interest. It will be carried out in two stages ;
(I) A small scale examination of around 30 deer brains to establish the normal histology of the healthy brain; and
(II) A larger scale random examination of 300 or more adult deer brains drawn from both deer farms and parks to establish whether there is any evidence of a cervine spongiform encephalopathy. ...
Ministry of Agriculture Fisheries and Food Veterinary Investigation Centre West House. Station Road. Thirsk Y07 IPZ Telephone: 0845·522065 Fax: 0845·525224
Your reference
Our reference RJH/ASB
Date 4 November 1992
DEER SPONGIFORM ENCEPHALOPATHY SURVEY
Dear Paul
I have now found time to review the 10 deer- brains collected from Mr Walker farm··via Winchester Via Winchester VIC. In answer to your specific question was there sufficient difference in preservation of brain tissue to warrant the extra effort involved in rapid brain removal on the farm, the answer is definitely "Yes." The original five brains (Winchester ref M487/11) showed varying degrees of autolytic vacuolation affecting both white and grey matter throughout the brain. vacuolation and separation of Purkinje cells and marked perivascular spaces. These artifacts made interpretation of subtle, specific pathological vacuolation more difficult. By contrast the second submission (Winchester reference N736/2) showed excellent preservation of white and grey matter. Any vacuolar Change present could be confidently interpreted as pathological albeit of unknown pathogenesis.
I can only reiterate the comments made by Gerald Wells and myself at the preliminary discussion at Weybridge in Autumn 1991. If the survey's purpose is an accurate histopathological interpretation of brain tissue. the material must be collected in a pristine state. This is particularly valid when looking for ar unrecognised and undefined spongiform encephalopathy in a new species. Deer brains are very large structures which take a lot of fixation and therefore must be handled sympathetically from the start. We have already seen the problems encountered in comparatively smaller hound brains where delayed fixation was a major limitation on interpretation of true pathological change.
The bottom line must be that if a pathologist's expertise is to be used, it is critical to collect artefact free brain material. If the politics or economics do not allow this, then I would suggest that an electron microscopy survey in­volving detection of scrapie associated fibrils would be much more appropriate.
Best wishes Yours sincerely
R J HIGGINS VIO 92/11.4/2.1
TSE in wild UK deer? The first case of BSE (as we now realise) was in a nyala in London zoo and the further zoo cases in ungulates were simply thought of as being interesting transmissions of scrapie initially. The big problem started to appear with animals in 1993-5 when it became clear that there was an increase in the CJD cases in people that had eaten deer although the statistics involved must have been questionable. The reason for this was that the CJD Surveillance was well funded to look into the diet of people dying of CJD. This effect is not clear with vCJD...if only because the numbers involved are much smaller and hence it is difficult to gain enough statistics. They found that many other foods did not appear to have much association at all but that deer certainly did and as years went by the association actually became clearer. The appearance of vCJD in 1996 made all this much more difficult in that it was suddenly clearer that the cases of sporadic CJD that they had been checking up until then probably had nothing to do with beef...and the study decreased. During the period there was an increasing worry that deer were involved with CJD.. see references: DEER BRAIN SURVEY
Subject: Re: DEER SPONGIFORM ENCEPHALOPATHY SURVEY & HOUND STUDY
Date: Fri, 18 Oct 2002 23:12:22 +0100
From: Steve Dealler
Reply-To: Bovine Spongiform Encephalopathy Organization: Netscape Online member
To: BSE-L@ References: <3daf5023 .4080804="" wt.net="">
Dear Terry,
An excellent piece of review as this literature is desparately difficult to get back from Government sites.
What happened with the deer was that an association between deer meat eating and sporadic CJD was found in about 1993. The evidence was not great but did not disappear after several years of asking CJD cases what they had eaten. I think that the work into deer disease largely stopped because it was not helpful to the UK industry...and no specific cases were reported. Well, if you dont look adequately like they are in USA currenly then you wont find any!
Steve Dealler 
===============
GAME FARM INDUSTRY WANTS TO COVER UP FINDINGS OF INCREASE RISK TO CJD FROM CERVID
BSE INQUIRY
CJD9/10022
October 1994
Mr R.N. Elmhirst Chairman British Deer Farmers Association Holly Lodge Spencers Lane
BerksWell Coventry CV7 7BZ
Dear Mr Elmhirst,
CREUTZFELDT-JAKOB DISEASE (CJD) SURVEILLANCE UNIT REPORT
Thank you for your recent letter concerning the publication of the third annual report from the CJD Surveillance Unit. I am sorry that you are dissatisfied with the way in which this report was published.
The Surveillance Unit is a completely independant outside body and the Department of Health is committed to publishing their reports as soon as they become available. In the circumstances it is not the practice to circulate the report for comment since the findings of the report would not be amended.. In future we can ensure that the British Deer Farmers Association receives a copy of the report in advance of publication.
The Chief Medical Officer has undertaken to keep the public fully informed of the results of any research in respect of CJD. This report was entirely the work of the unit and was produced completely independantly of the the Department.
The statistical results regarding the consumption of venison was put into perspective in the body of the report and was not mentioned at all in the press release. Media attention regarding this report was low key but gave a realistic presentation of the statistical findings of the Unit. This approach to publication was successful in that consumption of venison was highlighted only once by the media ie. in the News at one television proqramme.
I believe that a further statement about the report, or indeed statistical links between CJD and consumption of venison, would increase, and quite possibly give damaging credence, to the whole issue. From the low key media reports of which I am aware it seems unlikely that venison consumption will suffer adversely, if at all.
Recently the question has again been brought up as to whether scrapie is transmissible to man. This has followed reports that the disease has been transmitted to primates. One particularly lurid speculation (Gajdusek 1977) conjectures that the agents of scrapie, kuru, Creutzfeldt-Jakob disease and transmissible encephalopathy of mink are varieties of a single "virus". The U.S. Department of Agriculture concluded that it could "no longer justify or permit scrapie-blood line and scrapie-exposed sheep and goats to be processed for human or animal food at slaughter or rendering plants" (ARC 84/77)" The problem is emphasized by the finding that some strains of scrapie produce lesions identical to the once which characterize the human dementias"
Whether true or not. the hypothesis that these agents might be transmissible to man raises two considerations. First, the safety of laboratory personnel requires prompt attention. Second, action such as the "scorched meat" policy of USDA makes the solution of the scrapie problem urgent if the sheep industry is not to suffer grievously.
snip...
76/10.12/4.6
IN CONFIDENCE
SCRAPIE TRANSMISSION TO CHIMPANZEES
IN CONFIDENCE
reference...
RB3.20
TRANSMISSION TO CHIMPANZEES
1. Kuru and CJD have been successfully transmitted to chimpanzees but scrapie and TME have not.
2. We cannot say that scrapie will not transmit to chimpanzees. There are several scrapie strains and I am not aware that all have been tried (that would have to be from mouse passaged material). Nor has a wide enough range of field isolates subsequently strain typed in mice been inoculated by the appropriate routes (i/c, ilp and i/v) :
3. I believe the proposed experiment to determine transmissibility, if conducted, would only show the susceptibility or resistance of the chimpanzee to infection/disease by the routes used and the result could not be interpreted for the predictability of the susceptibility for man. Proposals for prolonged oral exposure of chimpanzees to milk from cattle were suggested a long while ago and rejected.
4. In view of Dr Gibbs' probable use of chimpazees Mr Wells' comments (enclosed) are pertinent. I have yet to receive a direct communication from Dr Schellekers but before any collaboration or provision of material we should identify the Gibbs' proposals and objectives.
5. A positive result from a chimpanzee challenged severely would likely create alarm in some circles even if the result could not be interpreted for man. I have a view that all these agents could be transmitted provided a large enough dose by appropriate routes was given and the animals kept long enough. Until the mechanisms of the species barrier are more clearly understood it might be best to retain that hypothesis.
6. A negative result would take a lifetime to determine but that would be a shorter period than might be available for human exposure and it would still not answer the question regarding mans' susceptibility. In the meantime no doubt the negativity would be used defensively. It would however be counterproductive if the experiment finally became positive. We may learn more about public reactions following next Monday' s meeting.
R. Bradley
23 September 1990
CVO (+Mr Wells' comments)
Dr T W A Little
Dr B J Shreeve
90/9.23/1.1.
IN CONFIDENCE CHIMPANZEES
CODE 18-77 Reference RB3.46
Some further information that may assist in decision making has been gained by discussion with Dr Rosalind Ridley.
She says that careful study of Gajdusek's work shows no increased susceptibility of chimpanzees over New World Monkeys such as Squirrel Monkeys. She does not think it would tell you anything about the susceptibility to man. Also Gajdusek did not, she believes, challenge chimpanzees with scrapie as severely as we did pigs and we know little of that source of scrapie. Comparisons would be difficult. She also would not expect the Home Office to sanction such experiments here unless there was a very clear and important objective that would be important for human health protection. She doubted such a case could be made. If this is the case she thought it would be unethical to do an experiment abroad because we could not do it in our own country.
Retrospectively she feels they should have put up more marmosets than they did. They all remain healthy. They would normally regard the transmission as negative if no disease resulted in five years.
We are not being asked for a decision but I think that before we made one we should gain as much knowledge as we can. If we decided to proceed we would have to bear any criticisms for many years if there was an adverse view by scientists or ­media. This should not be undertaken lightly. There is already some adverse comment here, I gather, on the pig experiment though that will subside.
The Gibbs' (as' distinct from Schellekers') study is somewhat different. We are merely supplying material for comparative studies in a laboratory with the greatest experience of human SEs in the world and it has been sanctioned by USDA (though we do not know for certain yet if chimpanzees specifically will be used). This would keep it at a lower profile than if we conducted such an experiment in the UK or Europe.
I consider we must have very powerful and defendable objectives to go beyond Gibbs' proposed experiments and should not initiate others just because an offer has been made.
Scientists have a responsibility to seek other methods of investigative research other than animal experimentation. At present no objective has convinced me we need to do research using Chimpanzees - a species in need of protection. Resisting such proposals would enable us to communicate that information to the scientist and the public should the need arise. A line would have been drawn.
CVO cc Dr T Dr B W A Little Dr B J Shreeve
R Bradley
26 September 1990
90/9.26/3.2
this is tse prion political theater here, i.e. what i call TSE PRION POKER...tss
3. Prof. A. Robertson gave a brief account of BSE. The US approach was to accord it a very low profile indeed. Dr. A Thiermann showed the picture in the ''Independent'' with cattle being incinerated and thought this was a fanatical incident to be avoided in the US at all costs.
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PAGE 26
Transmission Studies
Mule deer transmissions of CWD were by intracerebral inoculation and compared with natural cases {the following was written but with a single line marked through it ''first passage (by this route)}....TSS
resulted in a more rapidly progressive clinical disease with repeated episodes of synocopy ending in coma. One control animal became affected, it is believed through contamination of inoculum (?saline). Further CWD transmissions were carried out by Dick Marsh into ferret, mink and squirrel monkey. Transmission occurred in ALL of these species with the shortest incubation period in the ferret.
The occurrence of CWD must be viewed against the contest of the locations in which it occurred. It was an incidental and unwelcome complication of the respective wildlife research programmes. Despite its subsequent recognition as a new disease of cervids, therefore justifying direct investigation, no specific research funding was forthcoming. The USDA viewed it as a wildlife problem and consequently not their province! ...page 26.
snip...see;
IN CONFIDENCE
PERCEPTIONS OF UNCONVENTIONAL SLOW VIRUS DISEASE OF ANIMALS IN THE USA
GAH WELLS
REPORT OF A VISIT TO THE USA
APRIL-MAY 1989

why do we not want to do TSE transmission studies on chimpanzees $

5. A positive result from a chimpanzee challenged severly would likely create alarm in some circles even if the result could not be interpreted for man.
***> I have a view that all these agents could be transmitted provided a large enough dose by appropriate routes was given and the animals kept long enough.
***> Until the mechanisms of the species barrier are more clearly understood it might be best to retain that hypothesis.
snip...
DEER BRAIN SURVEY RED DEER ATAXIA OR CWD???
THURSDAY, APRIL 07, 2016 
What is the risk of chronic wasting disease being introduced into Great Britain? An updated Qualitative Risk Assessment March 2016 
Monday, May 05, 2014
Member Country details for listing OIE CWD 2013 against the criteria of Article 1.2.2., the Code Commission recommends consideration for listing
Friday, November 22, 2013
*** Wasting disease is threat to the entire UK deer population CWD TSE PRION DISEASE Singeltary submission to Scottish Parliament
Sunday, July 21, 2013
Welsh Government and Food Standards Agency Wales Joint Public Consultation on the Proposed Transmissible Spongiform Encephalopathies (Wales) Regulations 2013
*** Singeltary Submission WG18417
Friday, December 14, 2012
DEFRA U.K. What is the risk of Chronic Wasting Disease CWD being introduced into Great Britain? A Qualitative Risk Assessment October 2012
This assessment has been provided as an update to a previous version carried out in 2012, due to new evidence about the import of lures for deer hunting which contain deer urine. The previous assessment is available at:
Tuesday, July 17, 2012
O.I.E. BSE, CWD, SCRAPIE, TSE PRION DISEASE Final Report of the 80th General Session, 20 - 25 May 2012
THURSDAY, JUNE 12, 2025
Redefining the zoonotic potential of chronic wasting disease Singeltary Review

terry

posted by Terry S. Singeltary Sr. at 12:37 PM

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