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Evaluation of alternative antigens to PPDs for the diagnosis of caprine tuberculosis

Alberto Corroto Martín defended this Degree Final Project

July 4th, 2024

Improving the sensitivity (Se) and specificity (Sp) performance of official tuberculosis (TB) tests in goats is crucial as their limited performance leads to the existence of false positives and false negatives, with the associated economic, health and confidence implications. Therefore, great efforts have been devoted to the search and evaluation of new antigens that can replace classical PPDs, such as bovine PPD (PPDb) and avian PPD (PPDa), in order to improve the performance of official TB ante-mortem diagnostic tests.
This study focuses on evaluating two new antigens, DST-F and P22, as reagents in the official TB detection tests, the intradermal tuberculin test (IDTB) simple (IDTBs) and comparative (IDTBc) and the IFN-γ release assay (IGRA), in a goat herd with confirmed infection by isolation and culture of M. bovis. Sixty-five goats were selected from a farm with a 30% prevalence of TB and tested with various assays to compare the results obtained with these antigens with those of the PPDs (PPDb and PPDa) currently used in goat and bovine TB control programmes.
After the tests were performed, the increase in the skin of the animals was measured after the IDTBs, concluding that the inoculation of these antigens produced a lower skin reaction than after inoculation with PPDs. In addition, IGRA was performed, obtaining, according to the ELISA result, a production of IFN-γ , both in DST-F and P22, similar to that produced by PPDs.
Taking as a reference the results based on PPDs, it was observed that the IDTB tests with DSTF had a Se of 69% and a Sp of 94.5%, while in the IGRA a Se of 68.5% and a Sp of 93.5% were obtained; on the other hand, in the IDTB tests with P22 a Se of 80-83% and a Sp of 88.5-89% were found, and the IGRA with P22 presented a Se of 84% and a Sp of 93.5%.
Given these results, it was determined that the DST-F antigen underperformed PPDs in animals from an infected herd, while P22 showed more comparable results, detecting animals not identified by PPDs. This study provides new data on the performance of DST-F and P22 antigens but they need to be confirmed by further analysis to confirm the actual infection status of the animals tested and validate their use as effective diagnostic tools in the detection of caprine TB.
Keywords: Caprine tuberculosis, DST-F, P22, Intradermal tuberculin test, IGRA










Alberto Corroto Martín

TITLE: Evaluation of alternative antigens to PPDs for the diagnosis of caprine tuberculosis


TYPE: Degree Final Project


AUTHOR: Alberto Corroto Martín


DIRECTORS: Alvarez J. and Bezos J.


DATE: July 4th, 2024


LANGUAGE: English-spanish



CITE THIS PUBLICATION:

Alberto Corroto Martín. Evaluation of alternative antigens to PPDs for the diagnosis of caprine tuberculosis. Universidad Complutense de Madrid. July 4th, 2024. (Degree Final Project)


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