Comparison between two gamma-IFN assays and intradermal tuberculin test for the diagnosis of tuberculosis in water buffalo (Bubalus bubalis).

Control of tubercolosis (TB) in buffaloes is currently based on slaughter of animals deemed positive on the basis of tubercolin testing. This test presents some disadvantages such as the need of holding animals for 72 h and some difficulties depending on the interpretation and the site of the PPD inoculation. Therefore, the purpose of this preliminary study was to evaluate the use of the gamma-Interferon (gamma-IFN) assay as a confirmatory test under field condition in South of Italy. Animals from herds of known tubercolosis-positive status and from herds of known tubercolosis-negative status were tested in the last three years using the Intradermal Cervical Tuberculin Test (ICTT) and both the Prionics and IDVET gamma-IFN test. Different antigens (PPDS, ESAT-6, CFP10) were used in the vitro stimulation of blood lymphocytes of TB positive and negative animals to evaluate which reagent give the best results. The samples related to animals from herd TB free were negative for ICTT and for stimulation with recombinant proteins, while two samples reacted positively after stimulation with bovine PPD, demonstrating the specificity of improvement through the use of recombinant antigens. The results obtained in positive herds over the years demonstrate the ability of the gamma -IFN test to make early TB diagnosis compared to ICTT. The comparison between results of Prionics and IDVET tests performed on samples from infected herds, show a good correlation between the two kits.