Performance of TB immunodiagnostic tests in Eurasian badgers (Meles meles) of different ages and the influence of duration of infection on serological sensitivity

Sensitivity of the two serological tests was approximately 54% for both cubs and adults. Sensitivity of the IFNγ EIA was lower in cubs (57%) compared with adults (85%) when a common cut-off value was used to define test positivity. Taking data from the cubs alone, the IFNγ EIA cut-off value could be adjusted to increase the sensitivity to 71% with no loss in specificity. As a general observation, specificity of all tests was higher in cubs, although only significantly so in the case of the Brock Test. Using logistic regression analysis to adjust for age, sensitivity of the Brock Test was significantly lower at first culture positive event (58%), but increased to >80% as infection progressed.These data suggest that serodiagnosis could be a valuable tool for detecting a higher proportion of badgers with the greatest probability of transmitting infection. The age category of the badger appeared to exert little influence on the performance of the serological tests. Although data were only available for the IFNγ EIA in a small number of cubs, reduced sensitivity of the test in these individuals suggests a lower cut-off may be needed when testing younger animals.Despite attempts to control bovine tuberculosis (TB), by the end of 2007 the average incidence of disease in cattle in Great Britain (GB) had increased nearly 400% over the previous thirteen years [1], causing considerable economic loss to the farming community and high costs to Government. In parts of GB and Ireland, Eurasian badger (Meles meles) populations constitute a reservoir of Mycobacterium bovis infection and a potential source of infection to cattle [2-4]. Accurate diagnosis of M. bovis infection in badgers is an important component of the development of strategies to control TB in this species. Culture of M. bovis is still considered the 'gold-standard' diagnostic test. However, confirmation of TB in the badger by culture is particularly insensitive using clinical samples obtained from the live animal;