Detection of Johne’s Disease on dairy farms using different qPCR target genes for Mycobacterium avium subsp. paratuberculosis in young stock
Date
2023-08
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Abstract
Young stock can shed Mycobacterium avium subspecies paratuberculosis (MAP) in feces, present antibody titers and transmit MAP to other young stock. However, most Johne’s disease (JD) control programs do not include young stock in MAP testing strategies, which might be one of the reasons why only a few JD control programs were able to eradicate MAP. This study aimed to include young stock in a JD testing strategy and improve diagnostic tests. A literature review conducted reported that young stock can shed MAP as early as 4 mo of age. However, due to the chronic characteristic of the disease, it was considered important to improve current diagnostic tests and develop new tests, such as phage-based and metabolomics tests. A tentative inclusion of young stock in the MAP testing strategy was evaluated based on direct fecal qPCR and ELISA every 2 mo from animals between 2-12 mo of age. A sudden rise in MAP prevalence was detected at the second sampling, 2 mo after the start of the study. Although the high MAP prevalence was explained in part by the presence of MAP infections in the herd, it was not possible to explain the specificity of the ISMAP02 gene, which raises doubts about different Mycobacterium species being detected by the same assay. Furthermore, an in depth evaluation of the main MAP target genes for qPCR assays was proposed across different sample types and MAP concentrations. Overall, all MAP target genes were able to detect samples with high MAP concentration. IS900 and ISMAP02 consistently identified MAP in all sample types. However, the genes mbtA, hspX and F57 presented issues to detect samples with mid to low MAP concentrations.
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Keywords
calves, cattle, diagnostic tests, Mycobacterium avium subsp. paratuberculosis, Johnes disease
Citation
Martins, L. (2023). Detection of Johne’s disease on dairy farms using different qPCR target genes for Mycobacterium avium subsp. paratuberculosis in young stock (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.