|Robbe Austerman, Suelee|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 11, 2006
Publication Date: July 9, 2006
Citation: Stabel, J.R., Robbe Austerman, S. 2006. Early diagnosis of Johne's Disease: Evaluation of Methods [abstract]. American Dairy Science Meeting. p. 133. Technical Abstract: Measurement of secreted interferon-(IFN)-gamma has been suggested as a tool for the early detection of animals infected with mycobacterial pathogens,including Mycobacterium avium subsp. paratuberculosis, the causative agent of Johne's disease. Removal of infected animals at an early stage will help allay the spread of this disease through the herd. In the present study, the accuracy and reliability of the IFN-g and the intradermal skin tests were evaluated in calves born to naturally infected cows at different time points after birth. At 13-14 months of age calves were necropsied and tissue culture was correlated with results of the 2 assays. Ten of the 17 calves were tissue culture positive (TPos) for MAP and 7 were negative (TNeg). Within the TPos calves, the skin test identified 5 at 4-6 months of age, 4 at 6-8 months of age and 7 at 12-13 months of age. Comparatively, measurement of IFN-g identified 2 calves at 4-6 months, 4 at 6-8 months, and 10 at 12-13 months. Of the TNeg animals, the skin test identified 3 calves at 12-13 months of age, whereas the IFN-g identified 1 at 4-6 months, and 6 at the later time points. In a separate experiment, augmentation of secreted and intracellular IFN-g responses by intradermal injection of johnin purified protein derivative was achieve in adult cattle naturally infected with MAP. Intracellular IFN-gamma was higher within CD4+ and CD8+ subpopulations for infected cows compared to healthy controls throughout the study. When T cell populations were further defined by CD45RO+ expression, intracellular IFN-gamma was higher for CD8+/CD45RO+ lymphocytes compared to CD4+/CD45RO+ cells. These results indicate that intradermal sensitization of cows in the early stage of infection with antigen will enhance the sensitivity of detection by the IFN-gamma assay.