Assessment of the specificity of a gamma-interferon test performed with specific antigens to detect bovine tuberculosis, after non-negative results to intradermal tuberculin testing

In cattle herds in France, cervical skin tests (STs) using simple intradermal tuberculin (SIT) are performed to detect bovine tuberculosis (bTB). When positive results are found on ST screening, the herd is considered to be ‘under suspicion’ and confined, raising economic issues. The suspicion can be lifted by carrying out a single intradermal cervical comparative test (SICCT) at least six weeks later.The authors conducted an experimental study in France between 2013 and 2015 to assess the accuracy of the gamma-interferon test (IFN-γ), used in series after a non-negative result to ST screening, and to study the possibility of replacing the SICCT performed six weeks later by an IFN performed within a few days. Data were collected concerning 40 infected and 1825 bTB-free animals from herds with non-negative results to ST screening. This study showed that the IFN-γ test based on specific antigens and performed within a few days of a non-negative result to the ST has higher sensitivity than the SICCT performed six weeks later and equal specificity. The IFN test is more convenient to perform; however, it is more expensive. The IFN-γ test based on MIX antigens may be a useful alternative to the SICCT, to shorten the confinement period of suspect herds without underdetecting bTB.

Ante-mortem and post-mortem tuberculosis diagnostics in three European Bison from the enclosure in Bukowiec in the Bieszczady National Park in Poland

The ante-mortem diagnostics of tuberculosis in wildlife constitutes a major problem due to the difficulties in collecting samples for examination. Therefore, tuberculosis in free-living animals is usually diagnosed post mortem. Ante-mortem examinations for bovine tuberculosis (BTB) were conducted in three European bison living in an acclimatisation enclosure in Bukowiec in the Bieszczady National Park in Poland. The reason for performing these examinations was the documented contact between the aforementioned animals and tuberculous European bison from a free-living herd present in the area. The three European bison were pharmacologically immobilised. Next, their blood samples were collected for immunological studies (interferon-gamma release assays), complete blood count and blood biochemistry tests. Moreover, bronchoalveolar lavage (BAL) fluid from the lower respiratory tract, two nasal cavity swabs and one throat swab were taken from each animal. Tuberculin testing was also performed. The findings of all these examinations indicated the possible infection of the European bison with the tubercle bacillus. Ultimately, the decision was taken to euthanize the animals.