Comparison between a gamma-IFN assay and intradermal tuberculin test for the diagnosis of bovine tuberculosis in field trials in Brazil

• Published in: Journal of veterinary medicine. Series B 1999-06, Vol.46 (5), p.353-358
• Main Authors: Lilenbaum, W, Schettini, J.C, Souza, G.N, Ribeiro, E.R, Moreira, E.C, Fonseca, L.S
• Format: Article
• Language: English
• Subjects: Animals; bioassays; Brazil; Cattle; dairy cattle; diagnostic techniques; disease diagnosis; evaluation; Female; field experimentation; Immunoenzyme Techniques - veterinary; Interferon-gamma - blood; interferons; Mycobacterium; Mycobacterium bovis; Mycobacterium tuberculosis - immunology; risk assessment; Sensitivity and Specificity; serodiagnosis; tuberculin; Tuberculin Test - veterinary; Tuberculosis, Bovine - diagnosis; Tuberculosis, Bovine - prevention & control
• ISSN: 0931-1793; 0514-7166; 1439-0450
• DOI: 10.1111/j.1439-0450.1999.tb01240.x

Summary Bovine tuberculosis is a major problem in Brazil. The intradermal tuberculin test is the standard test for detection of bovine tuberculosis in Brazil but can lack both sensitivity and specificity. The purpose of this study was to compare a bovine γ‐IFN assay with the tuberculin test under field conditions in Brazil. A total of 1632 animals from 13 dairy farms were tested using the single cervical tuberculin test (SCTT). Among those animals, about 15% of each herd, 220 in total, represented a high‐risk group and were selected to be tested using the γ‐IFN test. Of the 1632 animals tested, 207 presented significant reactions representing 12.7% of the cattle studied. In the selected group the number of animals positive by the γ‐IFN assay was 126/220 (57.3%) and the total number of reactive cows on SCTT was 106/220 (48.2%). The real number of infected cattle, following standards, was 120/220 (54.5%). From these results the relative sensitivity rate of γ‐IFN test was 100% including the false‐positive results and 88.3% for the SCTT — a significant (P < 0.01) difference in favour of the γ‐IFN test of 11.7%. The γ‐IFN assay also identified some positive animals 60–120 days earlier than the SCTT. In conclusion, we believe that the γ‐IFN assay can be used alone or in combination with the SCTT, as a valuable tool for the control of bovine tuberculosis in the Brazilian national herd.