Presentation of the role of ANSES
Updated on 26/10/2017
Bovine tuberculosis, Zoonosis, Animal diseases
Bovine tuberculosis is an animal disease caused by a bacterium which is transmissible to humans. Both domestic and wild ruminants (mainly cattle and deer), as well as wild boar, badgers and foxes can be infected. Since 2001, France has been considered "officially free of bovine tuberculosis"; however each year about one hundred new outbreaks are reported in farms despite the control measures that have been implemented. Here we provide a presentation of the disease, its current status in France, and the role played by ANSES.
Bovine tuberculosis is an animal disease which can infect humans (zoonosis) and which is caused by Mycobacterium bovis (M. bovis). This bacterium can infect numerous domestic and wild ruminant species (mainly cattle and deer), in addition to wild boar, badgers and foxes. It is often transmitted through the respiratory route.
In cattle, the infection is often latent, with clinical symptoms only appearing late in the disease's generally long progression. However, although they may present few or no symptoms, infected animals may show reduced productivity and in some cases may also excrete the bacterium and contaminate humans as well as wild animal species (deer, pigs and boars, certain carnivores, etc.).
Since 2001, France has been considered "officially free of bovine tuberculosis" by the European Union, despite about one hundred outbreaks on farms each year. In certain départements like Côte-d’Or and Dordogne, the number of outbreaks has been rising regularly since 2004.
Domestic cattle are a primary reservoir for infection with M. bovis (save in exceptional cases), which means that the disease is transmitted first and foremost from infected cattle to healthy cattle. The eradication of bovine tuberculosis therefore implies above all controlling the disease in farms.
However, wild animals, in particular wild boar, badgers and deer, can also contract the disease. They therefore represent a secondary reservoir for the disease, and in turn are also able to contaminate farms.
Because of this, wildlife monitoring is conducted in order to prevent the infection from settling in these populations and leading to the creation of a primary reservoir as has been observed in other countries (with the badger in Great Britain and the wild boar in Spain, for example).
Highlighting the importance of wildlife in the disease's transmission cycle had led to strengthened screening for the disease in wildlife in proximity to domestic outbreaks.
ANSES's Maisons-Alfort Laboratory for Animal Health has been the National Reference Laboratory for bovine tuberculosis since 1999. In this capacity, it is in charge of devising analytic methods for the surveillance of the disease, and of transferring these methods to the network of approved laboratories that it coordinates throughout France.
For several years now, the Agency has also been conducting risk assessment work and providing regulatory support to the public authorities with regard to the disease. Since 2006, approximately twenty opinions on bovine tuberculosis have been issued by AFSSA and then ANSES.
In 2011, the Agency issued an expert report on the role of wildlife in the transmission and perpetuation of the disease. Following a formal request by the Ministry of Agriculture, ANSES created an expert group dedicated to handling these issues.
Based on this work, the Agency recommends, in addition to the existing measures for controlling tuberculosis in cattle herds:
regulating the density of deer and wild boar populations (on the rise over the last few years) by suppressing station-based supplemental feeding (providing additional food for wild animals), while complying with the national wild boar control plan and adjusting hunting plans;
setting up targeted badger culling measures and monitoring methods for evaluating the effectiveness of these measures, and boosting biosafety measures in farms in infected areas;
accounting for the risk of badgers spreading the disease outside currently infected areas (testing a representative sample of badgers around the culling areas);
preparing now for the possibility of embarking on a badger vaccination campaign with the help of the BCG in the event that the disease should spread through badgers outside the culling areas.
Finally, the Agency considers that research work should be undertaken to:
improve knowledge of M. bovis infection in wildlife (the density of the different species in the various environments, the size and stability of groups, modes of transmission of the disease between and within groups, M. bovis persistence in these living environments, frequencies of contact between wildlife and domestic cattle, and the specific virulence of different strains in this context).
prepare now for possible wildlife vaccination campaigns (in particular through collaborations with foreign teams that have undertaken vaccination trials).
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