Ronidazole in low concentrations in drinking water for treatment and development of immunity to swine dysentery.

The addition of ronidazole to the drinking water at the concentration of 0.003% was effective for the treatment of experimentally induced swine dysentery in swine. Ronidazole at concentrations of 0.0015% and 0.00075% aided in the treatment of swine dysentery and the development of immunity to the disease. In experiment I, in which swine were given concentrations of 0.003, 0.0015, and 0.00075%, there were more survivors, fewer days of hemorrhagic diarrhea, greater feed and water consumption and body weight gain, and more favorable feed efficiency in the medicated swine than in the nonmedicated swine. With the 0.003% concentration, there were no deaths, and the diarrhea receded during or after treatment with the 0.0015% and 0.00075% concentrations, the incidence of nonhemorrhagic diarrhea was greater in medicated than in nonmedicated swine, and the diarrhea did not subside during treatment. In experimetn II, there were more survivors in the groups of swine medicated with the 0.0015% concentration than in the nonmedicated groups of swine. All surviving nonmedicated swine in experiment I were immune to reexposure 3 months after initial exposure. More swine given to the 0.0015% and 0.00075% concentrations in the same experiment were immune to reexposure 3 months after initial exposure than were the swine given the 0.003% concentration. In experiment II, neither the swine previously medicated with the 0.0015% concentration nor the nonmedicated swine were immune to reexposure 5 weeks after initial expsoure. Large spirochetes were observed in fecal smears from all exposed swine which developed either hemorrhagic or nonhemorrhagic diarrhea.