Browsing by Author "Martins, Larissa"

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    An experimental model to induce digital dermatitis in beef calves
    (2022-06-23) Thomas, Anice D.; Pajor, Edmond A.; Caddey, Benjamin; Goldhawk, Christy; Martins, Larissa; Orsel, Karin
    Abstract Background Digital dermatitis (DD) is a multifactorial infectious disease affecting the skin on feet of cattle causing erosion and inflammation above the heel bulbs. Some cases of DD cause lameness and significantly impact animal welfare and productivity. While DD has emerged as a concern for the beef industry, key information regarding early detection and its impact on cattle behaviour is lacking. The primary objective of this study was to determine if an established DD experimental model for dairy calves could be used to induce DD lesions in beef calves. A secondary objective was to describe changes in behaviour and pain associated with induction of DD lesions. Eight beef calves acquired from a single cow-calf operator were enrolled in the study. Upon enrolment, calves were evaluated and determined to be free of foot lesions. Within the experimental environment, calves were housed in individual pens and assigned to two groups (mock-inoculated and inoculated). Both hind feet of each calf were enrolled. Within calf, inoculation protocol was consistent, and a 28-day experimental protocol was employed. Two days prior to inoculation, both hind feet of each calf were abraded (area above the heel bulbs and below the dewclaws), moistened, and wrapped to facilitate an anaerobic condition. Feet were inoculated with macerated DD lesion material or mock inoculum and remained wrapped until clinical signs of DD or protocol endpoint. Results After a period of 14 to 18 days post inoculation, three of five inoculated calves developed clinical signs (lameness), and upon close inspection, DD lesions were present on at least one hind foot. Two of five inoculated calves did not develop lesions within 28 days. Zero of three mock-inoculated calves developed DD. Treponema spp. were detected by quantitative polymerase chain reaction from biopsies of induced lesions. Measurements of behaviour prior to disease induction were numerically different between DD affected and mock-inoculated calves. Conclusions An experimental infection model established for dairy cattle was used to successfully induce acute DD lesions in three of five inoculated beef calves. This model can provide a framework to study intervention protocols and to evaluate the impact of DD on behaviour and pain.
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    Detection of Johne’s Disease on dairy farms using different qPCR target genes for Mycobacterium avium subsp. paratuberculosis in young stock
    (2023-08) Martins, Larissa; Barkema, Herman W.; Orsel, Karin; De Buck, Jeroen; Pearson, Jennifer
    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.