Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Abstract Only
Publication Acceptance Date: 7/5/2005
Publication Date: 11/7/2005
Citation: Palmer, M.V., Waters, W.R., Thacker, T.C., Minion, C.F., Greenwald, R., Esfandiari, J., Andersen, P., Mcnair, J., Pollock, J., Lyashchenko, K. 2005. Effects of different skin testing regimens on interferon gamma and antibody responses in cattle experimentally infected with Mycobacterium bovis [abstract]. American Association of Veterinary Laboratory Diagnosticians. p. 7.
Technical Abstract: Tuberculin skin testing, although a hallmark of tuberculosis eradication campaigns, lacks sensitivity and specificity and cannot be repeated for 60 days due to desensitization. To overcome these difficulties, an effective whole blood cellular immunoassay for bovine interferon-gamma (IFN-gamma) has been developed. The IFN-gamma test is commonly used in conjunction with skin testing as a confirmatory test following a positive response to the caudal fold skin test (CFT). The present study was conducted to determine the effect of different skin testing regimens on production of IFN-gamma using calves experimentally infected with M. bovis. Holstein calves were CFT tested 60 days post-inoculation and the comparative cervical test (CCT) 7 (immediate) or 60 (delayed) days later. In the CFT immediate CCT group, IFN-gamma responses increased temporarily at 3 days post-CFT, immediately followed by a decrease 7 days post-CFT (the day of CCT administration). IFN-gamma levels did not reach pre-CFT levels until 55 days post-CFT. In the CFT delayed CCT group, an increase in IFN-gamma production at 7 days post-CFT was followed by a decrease at 10 days post-CFT. IFN-gamma levels did not reach pre-CFT levels until 55 days post-CFT. After receiving the CCT at 60 days post-CFT there was a non-significant decrease in IFN-gamma production. Administration of the CFT to M. bovis-inoculated cattle induced antibody responses to M. bovis PPD, rMPB83 and the fusion protein Acr1:MPB83. Administration of the CCT either at 7 days or 60 days post-CFT boosted antibody responses to the same 3 antigens. Both IFN-gamma and antibody responses post-skin testing may be useful in identifying M. bovis infected cattle; however the timing of collection of such samples may influence interpretation.