Development of vertical transmission model for Bordetella bronchiseptica in pigs

Bordetella bronchiseptica can cause respiratory disease in a wide range of animal species. In pigs, it can cause severe respiratory infections in piglets and contribute to porcine respiratory disease complex (PRDC) in older animals. In the field, B. bronchiseptica is transmitted vertically from sow to piglet in the farrowing house or between piglets at weaning. Although B. bronchiseptica is most commonly spread from pig to pig, researchers routinely use direct inoculation with high doses of bacteria when testing intervention strategies. Although this method produces consistent disease, it does not replicate the dynamics of natural field infection. To generate a model that replicates field settings and assesses the complex interaction between host immunity, maternally derived immunity, and infection, we developed a vertical transmission model for B. bronchiseptica. Sows were inoculated with B. bronchiseptica two weeks pre-farrow and piglet colonization status was assessed 1-3 days post-farrow, 2.5 weeks post-farrow, and 3 weeks post-weaning. We found maternal antibody and the timing of B. bronchiseptica transmission varied between sows, with transmission in some animals occurring within 3 days of farrowing. Additionally, all exposed piglets were colonized by the post-weaning sampling. This work presents a novel B. bronchiseptica model using vertical transmission, which provides a natural exposure route and dose. This model will be useful for future work investigating B. bronchiseptica intervention strategies of neonatal pigs.