A comparison of Brachyspira hampsonii isolates and the evaluation of proteinase k vaccine preparations in swine

Brachyspira hampsonii has been an emerging cause of swine dysentery (SD) since the mid to late 2000’s. Before the isolation of B. hampsonii, Brachyspira hyodysenteriae was the thought to be the sole etiologic agent of swine dysentery and the primary cause of mucohemmorhagic diarrhea in pigs (MHD). Research has been performed examining both whole cell and engineered B. hyodysenteriae vaccines, but little to no research has been reported for B. hampsonii. Quantification of Brachyspira cultures has been determined by CFUs, PCR, and whole cell counts; however, these methods have not previously been compared within the same study. Limitations with CFU quantification due to the growth characteristics of Brachyspira spp. has also highlighted the need for alternate methods of viability assessment such as the 50% endpoint of hemolysis positive plates (HPP50) that is described herein. Further research is also needed to compare growth media and methods of Brachyspira cultivation in broth media, specifically. The first study in this thesis compared the virulence of four B. hampsonii isolates in eight-week-old pigs using a novel frozen broth inoculation method compared with a previously described fresh broth method. It was concluded that the fresh broth method produced earlier onset and a greater duration of MHD, although the frozen broth method did produce significant disease compared to the negative control pigs. The second study assessed the efficacy of two proteinase-K (PKT) digested prototype vaccines (one derived from B. hampsonii and one from B. hyodysenteriae) against a B. hampsonii challenge in 11-week-old pigs. This efficacy study showed a reduction in clinical days of SD and fecal shedding for the B. hampsonii vaccine (homologous challenge), but not the B. hyodysenteriae vaccine (heterologous challenge). These studies show the possibility of using a frozen broth method for B. hampsonii challenge models as well as further confirming the need for species-specific vaccines for Brachyspira