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Evaluation de nouveaux outils de diagnostic de la tuberculose bovine : Conditions d'utilisation d'un test de dosage d'IFNγ et d'un test PCR IS6110 en temps réel

Abstract : Due to a worrying increase of bovine tuberculosis (bTB) outbreaks in Dordogne since 2004 and because of the diagnostic deficiencies of conventional detection methods, like the single intradermal tuberculin test (SITT), bacteriology or systematic carcasses inspection at slaughterhouse, two new rapid diagnostic tools, (i) the modified interferon gamma (IFNγ) assay Bovigam® based on protein purified derivatives (PPD) and ESAT6 and CFP10 specific recombinant antigens (R) and, (ii) a real-time PCR method based on the detection of the insertion sequence IS6110 (PCR), were included in the current bTB control campaign in order to estimate their diagnostic value. The various studies carried out showed that PCR is at least as sensitive as bacteriology. Its operational specificity is very satisfying and its positive predictive value is excellent compared to bacteriology and histology. Therefore, it constitutes a rapid and reliable bTB diagnostic tool that, in case of positive skin tests or histology, avoids waiting for bacteriological results to confirm infection and thus reduces considerably the time needed for infection notification (about 2,5 months), which represents a crucial operational advantage. The application of the modified IFNγ assay as a tool for confirming non-negative SITT is not perfect but is an undeniable asset because of its SITT complementarity. From a technical point of view, a normalized calculation method of individual results must be used to obtain a better reproducibility and to allow establishing comparisons within a laboratory and between laboratories. Furthermore, it is necessary to adapt the analysis criteria (the decisional cut-off of the normalized formulae and the interpretation methods of the final result) to the regional infectious status on one hand (low or high prevalence area of bTB, rare or frequent non-specific reactions) and, on the other hand, to the test application conditions (in the general population or in the non-negative SITT population), for an appropriate use of the modified IFNγ assay. These satisfying findings led to the approval of the PCR IS6110 and the modified IFNγ assay as official confirmation tools of Tb infection and non-negative SITT respectively in August 2009.
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https://pastel.archives-ouvertes.fr/pastel-00541997
Contributor : Sandy Faye <>
Submitted on : Wednesday, December 1, 2010 - 4:00:47 PM
Last modification on : Tuesday, October 20, 2020 - 10:20:28 AM
Long-term archiving on: : Friday, December 2, 2016 - 11:31:05 PM

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Sandy Faye. Evaluation de nouveaux outils de diagnostic de la tuberculose bovine : Conditions d'utilisation d'un test de dosage d'IFNγ et d'un test PCR IS6110 en temps réel. Médecine vétérinaire et santé animale. AgroParisTech, 2010. Français. ⟨NNT : 2010AGPT0056⟩. ⟨pastel-00541997⟩

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