TitleApproaches towards optimising the gamma interferon assay for diagnosing Mycobacterium bovis infection in African buffalo (Syncerus caffer).
Publication TypeJournal Article
Year of Publication2011
AuthorsMichel, AL, Cooper, D, Jooste, J, de Klerk, L-M, Jolles, AE
JournalPrev Vet Med
Date Published2011 Feb 01
KeywordsAnimals, Animals, Wild, Antigens, Buffaloes, Interferon-gamma, Mycobacterium bovis, Mycobacterium fortuitum, Mycobacterium Infections, Nontuberculous, Predictive Value of Tests, Sensitivity and Specificity, Tuberculin Test, Tuberculosis

The application of diagnostic tests for bovine tuberculosis in wildlife poses formidable technical difficulties and the use of the gamma interferon assay offers a simplified approach to testing wild animal species. We compared the performance of the gamma interferon assay in African buffalo (Syncerus caffer) under the recommended guidelines for interpretation of test results and found a high sensitivity (92.1%) at the cost of a greatly reduced specificity (68.3%). The optimised cut-off value for positive test results under local conditions was identified at an optical density of 0.385 at wavelength 450nm as the preferred compromise between sensitivity and specificity. Additional optimisation approaches to improve test performance were examined and showed that the application of 'a priori exclusions' of test results on the basis of reactivity to fortuitum PPD (sensitin produced from Mycobacterium fortuitum) and to a lesser degree, avian PPD, increased specificity without losing sensitivity. The implications of these findings on a modified testing protocol adjusted to include measurement of immune responsiveness to fortuitum PPD and other interpretation schemes are discussed.

Alternate JournalPrev Vet Med
PubMed ID21122932