Risk assessment of bovine tuberculosis introduction and establishment in Norway

Sammendrag

VKM has assessed the risk of introduction and spread of bovine tuberculosis in Norway and cannot rule out that the disease still exists in Norway. There is a low risk of the disease being reintroduced with imported cattle, but the import of llamas and alpacas poses a greater risk. If the disease were to establish in Norway, there is a high risk of spread both among domestic animals and to wildlife. These are the main conclusions The Norwegian Scientific Committee for Food and Environment (VKM) has made in a risk assessment commissioned by the Norwegian Food Safety Authority. Background Following the outbreak of bovine tuberculosis in 2022, VKM was asked to investigate the risk of introduction as well as the risk of spread and establishment of the disease in Norway. The disease primarily affects cattle, but other animals and humans can also be affected. Bovine tuberculosis is a chronic disease that is difficult to diagnose. Therefore, it may take months or years before infected animals are detected. This makes it challenging to eradicate the disease. Conclusions With today's very limited import, VKM concludes it is unlikely that bovine tuberculosis will be introduced to Norway with cattle. Since neighboring countries Sweden and Finland are free from the disease, migration of wildlife will not pose a risk of introduction. However, as the source of the 2022 outbreak has not been identified, it cannot be determined if the disease is still present in Norway. “Alpacas and llamas pose a greater risk. These species are particularly susceptible to the disease, and animals have been imported to Norway, also from countries where the bacterium is common in the cattle population. It is therefore likely that the bacterium could be introduced to Norway with these species if imports continue”, says Eystein Skjerve, Scientific leader of the project team. There is significant trade and transportation of live animals (cattle, alpacas, and llamas) within Norway. If bovine tuberculosis were to establish here, such movements would pose a significant risk of spreading the bacterium. Furthermore, manure from infected herds could pose a risk of spreading to livestock and wild animals. Additionally, contact between livestock and wild animals, such as badgers, wild boars, and various deer species, could lead to the spread of the disease to the wild population. If bovine tuberculosis is established in Norway, a control and eradication strategy would require considerable time and resources. If the disease is introduced to-, and established in wild animal populations, experience from other countries indicates that it will be very challenging to eradicate the disease. “The risk of transmission of bovine tuberculosis to humans is generally low. Veterinarians, farmers, and slaughterhouse workers have an increased risk of infection. If the disease is established in Norway, the greatest risk of transmission to humans is through the consumption of both unpasteurised milk and dairy products”, Skjerve says. Risk-Reducing Measures VKM was also asked to identify several measures that could reduce the risk of introduction and establishment of bovine tuberculosis in Norway: Avoid importing animals from countries and regions where bovine tuberculosis is present in livestock. Avoid importing roughage to Norway from countries and regions with bovine tuberculosis. Increase testing requirements for the trade and movement of alpacas and llamas inside Norway. In the event of an outbreak of bovine tuberculosis, reduce contact between livestock and wild animals and routinely test wild animals (badgers, wild boars, and deer species). (...)