Bovine tuberculosis: ANSES reviews wildlife control measures
For almost 20 years, France has been officially free of bovine tuberculosis, a disease primarily affecting cattle herds. To maintain this status, surveillance and control actions aiming to bring the disease under control have been taken in certain at-risk areas. They include measures targeting infected herds, wild animals and the surrounding environment. After receiving a request from four associations, ANSES assessed the control measures applied to wildlife, especially badgers. ANSES confirms the importance of coordinated actions to effectively combat bovine tuberculosis and reiterates that the preventive culling of badgers and other wild species is in no way justified in disease-free areas.
A complex disease that requires an integrated approach
Bovine tuberculosis is an infectious disease transmissible to humans that is caused by the bacterium Mycobacterium bovis. France has maintained its disease-free[1] status since 2001 thanks to the control measures applied to affected cattle herds. However, a few outbreaks persist in certain départements and are currently covered by specific surveillance and management measures, making it possible for this “disease-free” status to be maintained. In addition to cattle herds, numerous wild animal species are likely to be infected, such as deer, wild boars and badgers. The possibility of the bacterium being spread between domestic fauna and wildlife partly explains the persistence of certain residual outbreaks and has led to the implementation of measures targeting both farms and wild animals. Moreover, recent research has demonstrated that the bacterium is resistant within the environment itself (burrows, pastures), so cattle can also be contaminated indirectly. The epidemiological situation concerning bovine tuberculosis is the result of complex interactions between several host species – cattle and various wild animals – and the environment, requiring that a comprehensive “One Health” approach be adopted to monitor and control this disease.
Badgers and bovine tuberculosis
Badgers are one of the wild species susceptible to bovine tuberculosis. They are difficult to study since they are nocturnal and live in burrows known as setts. The transmission of the bacterium between badgers, and between badgers and other animal species, depends in particular on the number of direct and indirect contacts between animals and their population densities. Due to the highly variable behaviour of badger populations, comparisons between regions and countries should be analysed with caution. Local case-by-case investigations should always be undertaken. Studies conducted in France have shown that badgers play a role in the epidemiological cycle of tuberculosis in the Côte-d’Or département. Elsewhere in the country, this role still needs to be clarified, even though historical data tend to support this hypothesis.
Locally appropriate measures
Following ANSES's recommendations in 2011, a surveillance scheme for bovine tuberculosis in wildlife was deployed in France. “Sylvatub”, as it is known, is currently part of the French National Epidemiological Surveillance Platform for Animal Health (ESA). The scheme consists in monitoring the progression of the disease and precisely locating at-risk areas around disease outbreaks in cattle where contact with wildlife is possible. By collecting these data, it is possible to continuously tailor wildlife control measures so as to eradicate the disease in cattle herds.
Current laws closely regulate surveillance and control measures leading to the culling of wild animals, according to the area and level of infection. Measures relating to badgers can therefore only be implemented in a specifically demarcated area that is regularly reassessed based on surveillance data. Moreover, operations must be preceded by an inventory of badger setts in the area. These control measures only apply to at-risk areas in a few French départements, which accounted for less than 4% of mainland France in 2018. Regarding other types of measures, vaccination is currently in the experimental stage, and ANSES is collaborating in research work to develop an oral vaccine.
After analysing the control measures currently in place, ANSES confirms that only coordinated actions can effectively bring bovine tuberculosis under control, by targeting cattle in infected herds, wild animals and the surrounding environment. While these measures do not currently threaten the badger species in France, ANSES's experts reiterate their recommendations from 2011, which stress that the preventive culling of badgers and other wild species in disease-free areas is in no way justified in the fight against tuberculosis.
[1] Criteria determining disease-free status for bovine tuberculosis:
- the annual prevalence of infected herds has remained below 0.1% for six years;
- the rate of officially tuberculosis-free herds has remained above 99.9% for six years as of 31 December of each year;
- compliance with the European regulations (Directive 64/432/EEC) on tuberculosis.