Exacerbated onset of dysentery in swine vaccinated with inactivated adjuvanted Serpulina hyodysenteriae.

After oral challenge exposure with Serpulina hyodysenteriae-infected diced colon, fewer swine vaccinated with an experimental vaccine adjuvanted with mineral oil died (8 of 25 [32%]) than did nonvaccinated controls (6 of 15 [40%]), although the difference was not significant. However, onset and exacerbation of dysentery were accelerated in vaccinated swine because: 5 of the 8 dead vaccinated swine died before any of the nonvaccinates, which was significant (P < 0.01); vaccinated swine that died were observed to have more hemorrhage in the feces, colonic mucosa, and colonic lumen than did nonvaccinated swine; and the earlier diarrhea onset in vaccinates, the more days of hemorrhagic diarrhea (P < 0.05). Antibody titer in vaccinated swine immediately before challenge exposure that subsequently died was significantly (P < 0.05) higher than that in vaccinated swine that recovered. Of of the 30 swine vaccinated with the experimental vaccine, 20 had dispersed droplets of mineral oil at the site of vaccination in the neck muscles and 3 swine had purulent abscesses at the injection site. It was concluded that vaccination with the experimental vaccine for controlling swine dysentery was ineffective.