Tuesday, March 19, 2013

March 19, 2013 at 11:48PM Effect of transportation, time of sampling, and lymphocyte numbers on gamma interferon response to Mycobacterium bovis in cattle at time of slaughter

Adapting the gamma interferon (IFN) assay for tuberculosis screening at points-of-concentration of cattle would improve global efforts to eradicate bovine tuberculosis. Two separate studies were conducted to evaluate if transportation of cattle, the time of blood collection, and total lymphocyte count affects the retention of a positive IFN assay result during slaughter of cattle experimentally sensitized with inactivated Mycobacterium bovis. Study 1 evaluated IFN assay responses to M. bovis and Mycobacterium avium stimulations in 5 cows (4 sensitized and 1 control) at the housing facility, after a 30-min transport to the slaughter facility, immediately before stunning, at commencement of exsanguination, and at 5 min after exsanguination commenced. Study 2 evaluated IFN assay responses to Mycobacterium antigen stimulations and total lymphocyte count in blood collected from 5 steers (4 sensitized and 1 control) at the housing facility, at commencement of exsanguination and at 2 successive 1-min intervals. The results indicated that blood obtained from sensitized cattle at commencement of exsanguination was more likely to remain positive than blood collected at successive time points; hence the time of blood collection is crucial to obtaining a useful IFN assay result for bovine tuberculosis at slaughter. The lymphocyte count progressively declined following exsanguination, and this decline might contribute to the reduction in the measured IFN. To compensate for the reduction in IFN production, a different set of positive cutoff values might be needed for blood collected at exsanguination. The current findings provide useful preliminary information necessary for making changes to the interpretation of the IFN assay on blood collected during exsanguination.






via Journal of Veterinary Diagnostic Investigation recent issues http://vdi.sagepub.com/cgi/content/abstract/25/2/248?rss=1

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