Location: Infectious Bacterial Diseases ResearchTitle: Comparison of sheep, goats, and calves as infection models for Mycobacterium avium subsp. paratuberculosis Author
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/5/2018
Publication Date: N/A
Technical Abstract: Introduction: Animal infection models to study Mycobacterium avium subsp. paratuberculosis (MAP) infection are useful for evaluating the efficacy of vaccines and other therapeutics for the prevention or treatment of infection. Because Johne’s disease is highly prevalent in US dairy cattle populations much of our research utilizes neonatal calves as infection models. Disadvantages to a calf model are the expense and that they do not generally progress to clinical disease within a 12-month period. Objective: The goal of the present study was to compare sheep, goats, and calves as infection models, perhaps demonstrating clinical signs within a shorter time span. Materials and methods: In the present study neonatal sheep, goats, and calves (n=4) received 109 cfu of a cattle isolate of MAP in milk replacer on days 0, 3 and 6 of a 12-month study and sampled monthly during the study period. Results: Results demonstrated a robust antigen-specific IFN-g response at 90 days post-inoculation for sheep and goats with lower responses noted for calves. By 360 days, IFN-g responses were 50 and 82% higher for calves than for goats and sheep, respectively. Although MAP-specific antibody responses were first observed in sheep at 90 days, calves had higher antibody responses throughout the remainder of the study. Following pass-through shedding on day 7, fecal shedding was fairly negligible across treatments but remained higher for calves throughout the study. Colonization of tissues was variable within treatment group but trended higher for calves and sheep for the majority of tissues. Interestingly, upon stimulation of PBMCs with a whole-cell sonicate of MAP, flow cytometric analyses demonstrated greater populations of CD4+ T cells and lower populations of NK and CD14+ cells for goats and calves compared to sheep. Conclusions: Although sheep and goats have many similar properties as infection models to calves, overall calves proved to be a more standardized model with appropriate fecal shedding, tissue colonization and host immune responses upon long-term infection.