AUTHOR=Encinas Micaela , Ferrara Muñiz Ximena , Sammarruco Romina Ayelén , Ruiz Menna Victoria , Garro Carlos Javier , Delgado Fernando , Macías Analía , Magnano Gabriel , Zumárraga Martín José , Garbaccio Sergio Gabriel , Eirin María Emilia TITLE=Limited usefulness of the IS6110 touchdown-PCR in blood for tuberculin skin test false-negative cattle with serological response to Mycobacterium bovis JOURNAL=Frontiers in Veterinary Science VOLUME=11 YEAR=2024 URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2024.1359205 DOI=10.3389/fvets.2024.1359205 ISSN=2297-1769 ABSTRACT=

Ante-mortem diagnosis of bovine tuberculosis (bTB) is based mainly on the tuberculin skin test (TST) and the ɣ-IFN release assay (IGRA). Some infected animals escape screening tests, thus, limit herd sanitation. Previous reports have suggested a predominant pattern of multi-organ lesions attributable to Mycobacterium bovis (the causative agent of bTB) bacteraemia. A case–control study was conducted to investigate blood PCR as an alternative tool for improving ante-mortem detection of TST false-negative bovines. Cases comprised 70 TST false-negative bovines (cases), which were serology positive, and controls included 81 TST positive bovines; all of them confirmed as infected with M. bovis. Detection of the IS6110 target through touchdown blood-PCR (IS6110 TD-PCR) was performed. The positivity of the blood-PCR was 27.2% in the control group. This performance was similar to the 15% obtained among cases (p = 0.134). Most cases identified by the IS6110 TD-PCR exhibited focalized lesions (p = 0.002). Results demonstrated that blood-PCR could detect TST false-negative cattle, even if they are negative for IGRA. Considering that cases exhibited humoral response to M. bovis, further studies conducted in a pre-serological stage could provide evidence about the real contribution of the technique in herds.