CWD in Norway

The Norwegian Food Safety Authority (NFSA) and Norwegian Environmental Authority (NEA) asked the Norwegian Scientific Committee for Food Safety (Vitenskapskomiteen for mattrygghet, VKM) for an opinion on factors associated with the introduction of Chronic Wasting Disease (CWD) to Norway. VKM appointed a working group consisting of two members of the Panel on Biological Hazards, one member of Panel on Animal Health and Welfare, and two external experts to prepare the answer to the questions. The Panel on Biological Hazards has reviewed and revised the draft prepared by the working group and approved the opinion. CWD was diagnosed in March 2016 in a wild reindeer (Rangifer tarandus) from the Nordfjella mountain area in Norway and in May and June in two mooses (Alces alces) in Selbu in South Trøndelag County, approximately 300 km north from the first case. There is currently no information to determine the origin(s) of CWD agents in Norway. However, the sporadic or genetic (somatic mutation) occurrence of prion disease in cervids cannot be excluded, nor can introduction from North America or other countries. Furthermore, there is no evidence that it has not been circulating at low levels in the Norwegian cervid populations for years, but has not previously been identified. In this scientific opinion, information on prion diseases in general, and CWD in particular, is presented in the light of experiences with this disease in North America. Prions are among the most resilient pathogens known and dissemination of prions into ecosystems is likely to result in long-term problems. Prions bind strongly to soil and remain infectious. In CWD, prions are present in most peripheral organs and also shed into the environment via saliva, faeces, and urine, as well as with the placenta. CWD transmits easily among cervids, either through direct contact, or indirectly via the environment. Migration of animals is relevant for the spread between areas. Strain diversification might occur in CWD and may influence transmission properties of the agents. Clinical signs of CWD are non-specific and do not alone enable confirmation of the diagnosis. Analysis of tissue from the brainstem at the level of the obex by approved methods is necessary for diagnosis of CWD. Prion infectivity is assessed by bioassays, often involving transgenic mice. In vitro conversion assays, like protein misfolding cyclic amplification (PMCA), provide sensitive quantification of converting activity, which is a good approximation of infectivity. Genetic variation (polymorphisms) in the gene that encodes PrP (PRNP) can modulate sensitivity towards CWD. The level of such genetic variation in Norwegian wild and semi-domesticated cervids is currently unknown. Cattle and sheep are at very low risk of developing CWD and it is highly unlikely that prion diseases in sheep or cattle are the origin of CWD. Although transmission of CWD to humans has never been known to occur, and animals other than cervids have not been found to be infected, indicating a species barrier, this possibility cannot be excluded. Thus, measures for reduction of human exposure are recommended. Taking into account uncertainties regarding the plasticity of the CWD agents and the lack of transmission data from the Norwegian isolates, this scientific opinion considers the zoonotic risk of CWD to be very low.

CWD in Norway – A State of Emergency for the Future of Cervids (Phase II)

The Norwegian Food Safety Authority (Mattilsynet, NFSA) and the Norwegian Environment Agency (Miljødirektoratet, NEA) requested the Norwegian Scientific Committee for Food Safety (Vitenskapskomiteen for mattrygghet, VKM) for a scientific opinion on Chronic wasting disease (CWD) in cervids. The project was divided into two phases, and VKM published the scientific opinion from phase I “CWD in Norway” in June 2016. The current report is the result of phase II. VKM was asked to provide updated information on food safety, aspects important for transmission of CWD within and between populations and species, and the potential origin of the disease in Norway. Moreover, VKM was asked to highlight important risk factors with regard to disease transmission, and how these risk factors might affect choice of management strategy. Finally, VKM was asked to highlight relevant management strategies from North America or elsewhere. VKM appointed a working group consisting of one member of the Panel on Microbial Ecology, one member of the Panel on Biological Hazards, and five external experts, as well as VKM`s secretariat to answer the questions from NEA and NFSA. One member of the Panel on Alien Organisms and Trade in Endangered Species (CITES), one member of the Panel on Animal Health and Welfare, as well as one member of the Panel on Biological Hazards commented on the draft report. The Panel on Biological Hazards assessed and approved the final report. Background: Chronic wasting disease (CWD) is a prion disease that affects deer, moose, reindeer, and related species (cervids). Prion diseases are chronic neurodegenerative diseases that occur naturally in humans and ruminants, and are invariably fatal. Some prion diseases, such as classical scrapie in sheep and goats and chronic wasting disease (CWD) in cervids, are contagious, spreading directly between animals or via environmental contamination. In contrast, prion diseases known to affect humans are not known to be contagious. Prions are extraordinary agents consisting of misfolded protein aggregates that are remarkably stable and can remain infectious for years in the environment. Prion proteins are present in most animals, but the misfolding makes them very hard to break down. Consequently, misfolded prion proteins accumulate in the brain and eventually in other tissues, causing damage to those tissues. Until recently, CWD was only known from North America and South Korea. During a routine marking event in April 2016, a female reindeer (Rangifer tarandus) of the Nordfjella wild reindeer herd in Norway exhibited unusual behaviour, and died shortly afterwards. This unusual death was routinely investigated, and the animal was diagnosed with CWD. This was the first time CWD had been diagnosed outside North America and South Korea and the first case of natural CWD in reindeer. In addition, two moose (Alces alces) in Selbu, Norway were diagnosed with CWD in May 2016. Selbu is located approximately 300 km northeast of the Nordfjella mountain range. Currently there is considerable uncertainty regarding the nature of the CWD diagnosed in the two moose. Some of the characteristics of these cases indicate consistency with atypical prion disease, as described in domestic animals, but a final conclusion depends on the results from ongoing investigations. Following the diagnosis in reindeer, Norwegian authorities initiated a screening programme in which hunters were requested to collect tissue and the heads of dead cervids during the 2016 hunting season. Animals that had died from causes other than hunting were also tested for CWD. Since March 2016, 4629 samples of moose, 2550 samples of red deer, 627 samples of roe deer, 860 samples of reindeer, 2494 semi-domesticated reindeer, 163 farmed deer and 104 samples of unidentified species were tested for CWD. Two additional cases of CWD were diagnosed in wild reindeer in the Nordfjella population. Together with a clinical, pathological and epidemiological picture consistent with contagious CWD, as described from North America, this indicated that there is an ongoing outbreak of CWD in the wild reindeer population of the northern part of Nordfjella wild reindeer range. Results: An increase in the distribution and prevalence of CWD will increase exposure of other species, including domestic animals and humans, to this infectious agent. There is currently no evidence indicating transmission of CWD to domestic animals or humans, either by direct contact with cervids, cervid meat, or other products from cervids, or through the environment. VKM continues to support the conclusion from phase I concerning food safety of meat from cervids, that the zoonotic risk of CWD (transmission to humans) is very low. Preliminary results from characterisation of the moose cases and the agent involved indicate that important features deviate significantly from those found in the reindeer and in North American cervids, raising uncertainty with regards to the zoonotic potential. Therefore, based on the data currently available, VKM is not able to reach an evidence-based conclusion regarding the food safety of meat from moose and other cervids infected with this potentially new variant of CWD. Whereas direct transmission (animal-to-animal) seems most important in the early phases of a CWD epizootic, the role of indirect transmission (from the environment) increases as the prevalence increases. Once contagious CWD is established, it is very likely that the disease will increase in prevalence within the affected population and spread to contact populations. The rate of increase in prevalence, the resulting impact in a given population, and the efficacy of spread will depend on a range of environmental factors, and the characteristics of the species and population in question. For example, in affected populations of a gregarious species like reindeer, CWD is likely to lead to population decline in the long-term. Experiences from North America indicate that prions aggregate in the environment, making eradication of the disease extremely difficult once it has been allowed to develop and become endemic. It is therefore important that efficient measures are implemented at the VKM Report 2017:9 9 earliest opportunity in order to have a realistic chance of eradicating local occurrence of CWD and preventing further spread. Contagious CWD found in a confinable population, such as many wild reindeer herds, should be managed by eradication of the host population, fallowing of the area (> 5 years), and restocking from a healthy population. The report explains that culling of the Nordfjella reindeer herd is a necessary, immediate response to the current situation. However, as part of an adaptive management strategy, this measure should be under active review and may be revised in the event that new cases of CWD are discovered. In contrast, in continuous populations, such as most red deer, moose, and roe deer populations, spatially targeted culling within a defined containment zone should be used to control a CWD outbreak. Confinement of CWD-infected populations should be increased where possible and contact with other populations of cervids restricted, for example by fencing, herding, enhancing natural or man-made obstacles, or decreasing the densities of the relevant cervid populations. Potential “hotspots” for disease transmission (supplementary salt-licks, supplementary feeding sites etc.) should be eliminated in areas with CWD as well as the surrounding areas, and should further be considered for other parts of the country. Precautionary measures should be implemented to prevent anthropogenic spread of the disease. Finally, increasing the national surveillance of CWD in cervids is essential to ensure that there is a comprehensive basis for future evidence-based management. This is required to ensure that cases and spread of disease are identified as soon as possible, as late discovery will limit the chances for successful eradication of CWD in Norway.

Human Pathogens in Marine Mammal Meat

Background: Norway conducts commercial hunts for seals and whales, and since marine mammal meat and products are distributed to the public, these products are covered by the general hygiene control regulations. The control of meat from marine mammals is based primarily on organoleptic and microbiological spot tests. There is a general lack of knowledge available on the presence of potential zoonotic pathogens in marine mammal meat and products and on the potential risk for humans. The Norwegian Scientific Committee for Food Safety (Vitenskapskomiteen; VKM), Panel of Biological Hazards (Faggruppe hygiene og smittestoffer) took the initiative to develop this risk assessment in order to identify possible risks associated with human consumption of meat and products from seals and whales. The risk assessment is based on scientific publications and reports, and documents that have been used for training of veterinary personnel in meat control. Animal welfare is not within the scope of this assessment. Main Conclusions: It is documented in this assessment that marine mammals may harbour several pathogens with the potential of giving disease in humans, and there are some reports on the transfer of such agents via meat from seals and whales. The Panel of Biological Hazards has not been able to document that human consumption of meat from seals and whales is associated to a risk of exposure to human pathogens in Norway, but the data on which this conclusion is build, is scarce and are too limited to draw firm conclusions. There are almost no data documenting the microbiological status of seal and whale meat that is distributed for human consumption and the control is ad hoc, based on spot tests and few animals. The general trend of increased consumption of raw or lightly cooked food may increase the risk for transmission of pathogens to humans. Considered suboptimal conditions for hygienic treatment of meat on board, as compared to abattoir conditions, as well as a long storage time in a non-frozen state (whale meat), it is crucial to secure the hygienic quality of the meat. The training of personnel in slaughter hygiene should be strengthened, and if meat is not frozen, an unbroken cold-chain should be documented through the production line from the slaughter to the retail level. A more systematic meat control practice (routine control) should be established. Broad-scale research projects, focusing on human pathogens in seals and whales, as well as monitoring and collating of data on contamination, are needed to further explore the risks of transmission of human pathogens from marine mammal meat.