Eradication of Chronic Wasting Disease is not completed
This is the key message from an update of previous risk assessments of CWD conducted by the Scientific Committee on Food and Environment (VKM). The update was requested by the Norwegian Food Safety Authority.
VKM has assesseda number of different factors that can affect the spread of CWD within and out of the Nordfjella area. The area includes the entire Aurland, Lærdal and Hemsedalmunicipalities and parts of Ål, Hol, Eidfjord and Ulvik municipalities. Centrally located in the area is the Nordfjella wildlife area, divided into a zone 1in the north and a zone 2in the south. The wild reindeer population in zone 1was culledin the attempt to eradicate CWD.
The infectious agent in CWD, misfolded prions, is highly resistant. Prions can remain infectious in the environment for many years, and may bind to soil orbeing taken up by plants. Infected animals can shed prions, for example through saliva, urine and faeces, and thus infect other animals directly. The contamination can also persist in the environment and may be picked up by animals susceptible to infection.
The number of mineral lick sites used by the culled wild reindeer population and which are still accessible to animals will have a very important impact on the likelihood ofspread of infection from the environment, "says BjørnarYtrehus. He was the chair of project group that conducted the update.
Making the mineral lick sites inaccessible would reduce the probability of cervids entering zone 1 from becoming infected. The absence of mineral lick sites would also reduce the likelihood that sheep spread the infection, he continues.
If there still are infected animals in the area or new animals are infected from the environment, newly established mineral lick sites inside and outside of Zone 1will also increase the likelihood of spread of infection, Ytrehus emphasizes.
Significant uncertainty is attached to the identified factors. The likelihood of spread of infection can be reduced by maintaining intensive monitoring, alertness and preparedness.
In addition, fewer mineral lick sites and other places where animals gather would reduce the likelihood of spread of infection. Measures such as fencing and herding, reduction of cervid population and information to people using the area would also reduce the likelihood of spreading, says Ytrehus.
VKMs Panel on Biological Hazards has prepared the assessment.