Assessment of the cost-effectiveness of alternative bovine tuberculosis surveillance protocols in French cattle farms using the mixed interferon gamma test

Spatial association of Mycobacterium bovis infection in cattle and badgers at the pasture interface in an endemic area in France

Despite control and surveillance programmes, Mycobacterium bovis, the main aetiologic agent of bovine tuberculosis (bTB), is still detected on cattle farms and in wildlife populations in France, especially in badgers in the French Côte-d'Or département. The aim of our study was to find out if infected badgers were trapped significantly closer to pastures of infected farms than non-infected badgers and, if so, to determine the most efficient distance around those pastures for badger trapping, particularly for surveillance purposes. We studied two subareas (southern and northern), chosen based on natural barriers to badger movements and according to the presence of pastures belonging to infected farms (POIFs) and infected or non-infected badgers. In each subarea, we computed the shortest distances D0 and D between badgers trapped a given year n between 2015 and 2019 (n = 59 infected and n = 1535 non-infected badgers for D0; n = 53 infected and n = 1476 non-infected badgers for D) and POIFs designated as infected between the year n - 4 and n + 1 (respectively n = 373 and n = 388 POIFs). D0 was calculated without considering spoligotypes, while D was calculated considering the possible epidemiological link between infected badgers and POIFs by using bTB spoligotype information. Then, we computed the observed mean and median of the D0 and D distances and used a bootstrap analysis to test if infected badgers were found significantly closer to POIFs than non-infected badgers. We observed that infection of badgers was not independent of distance from POIF in both subareas but distances (D0 or D) were different between the northern and southern subarea. In the northern subarea, which displays a mosaic landscape (mean and median D distances were respectively 612 m and 303 m for infected badgers), infected badgers indeed were trapped closer to POIFs, considering D0 and D. In the southern subarea, predominantly forested, infected badgers were significantly closer to POIFs than non-infected badgers when considering D0 but not for D (mean and median D distances were respectively 7148 m and 4831 m for infected badgers). These results will help to determine the most efficient distance from POIFs to trap badgers to determine their infection status in countryside landscapes. They also highlight the need to better understand the epidemiological systems at play in more forested landscapes where badgers may behave differently or other susceptible sympatric wild species might play a more important role in the circulation of M. bovis, both phenomena contributing to badger infection at greater distances from POIFs.

A framework for multicriteria decision-aid analyses in animal health surveillance applied to periodic screening for French bovine tuberculosis

In animal health surveillance, decision-makers must allocate limited financial and human resources, choosing appropriate protocols that consider technical, economic and human aspects (i.e. test sensitivity, cost benefits and policy acceptability respectively). Choosing in an objective manner and considering all these criteria can be challenging, especially where criteria have a tendency to be at odds with one another. In France, there are several mandatory protocols implemented to screen for bovine tuberculosis (TB), each with advantages and drawbacks concerning effectiveness, cost and acceptability. Previous studies have developed scenario tree models in order to evaluate mandatory periodic screening protocols and alternative protocols. Using these previously developed models, we estimated protocol sensitivity, costs at the level of State and farmer, probability of false suspects, and probability of culling an uninfected animal, which influence stakeholders' acceptability. We then assessed the level of difficulty for protocol implementation for veterinarians, farmers and State through the use of surveys. Using these criteria, we rank the protocols with the PROMETHEE method, a multicriteria decision-aid method, by considering the relative importance of each criterion from the decision-maker point of view in four administrative areas with contrasting epidemiological context. This method can be considered a tool to aid decision-makers in choosing the appropriate protocol to apply to a heard while considering the technical and socio-economic facets of the problem. Additionally, by adapting the criteria to specific issues with regards to decision-making, there is potential for applying the PROMETHEE method to other animal health surveillance problems.