Influence of general anaesthesia on the vitality of peripheral leucocytes and first steps into the development of an interferon-gamma (IFN-gamma) release assay for the testing of red deer blood samples

Interferon-gamma release assays are used for the diagnosis of tuberculosis (TB) in cattle as well as several other species. They rely on the measurement of IFN-gamma, which is produced by sensitised T-cells after an infection with intracellular microbes. In Germany and the adjacent Austrian regions, red deer, as a reservoir of Mycobacterium caprae, plays an important role in the transmission and maintenance of TB. Therefore, ante mortem diagnostic approaches for TB, such as the development of an IFN-gamma release assay for this species are of crucial need. As wild animals have to be immobilised for blood withdrawal for this test, we investigated whether general anaesthesia has an influence on the vitality of leucocytes as the main source of IFN-gamma. In blood samples of cattle (collected before and during anaesthesia), IFN-gamma-concentrations were measured with a bovine IFN-gamma release assay and resulted in either equal values or were slightly higher during anaesthesia. Thus, we were able to confirm that there is no loss of leucocyte activity and consequently no decreased IFN-gamma production under narcotics. Furthermore, we explored if the bovine assay can be used for examining red deer blood samples. Whole blood samples of two anaesthetised red deer were tested and resulted in a very good cross-reaction between the bovine antibodies and cervid IFN-gamma. The applied bovine assay can be used for future examination of red deer blood samples to measure released IFN-gamma. To use it as a diagnostic tool for TB in red deer, further development of the assay would be required.