Ronidazole in high concentrations in drinking water for treatment and prevention of diarrhea in swine dysentery.

Ronidazole administered in the drinking water at concentrations of 0.012, 0.006, and 0.003% was effective for the treatment of swine dysentery. All groups of medicated swine had more survivors, fewer days of hemorrhagic and nonhemorrhagic diarrhea, greater feed consumption, greater weight gain, and more favorable feed efficiency than did nonmedicated swine. The only adverse clinical sign and lesion observed in the medicated swine comprised the drug-delayed-augmented swine dysentery which affected 3 swine in a group given 0.003% ronidazole. Several of the swine given the 0.012% concentration developed nonhemorrhagic diarrhea while on medication, probably because of the high concentration of the drug. Diarrhea did not recur in swine after the withdrawal of medication in both of 2 groups given the 0.012% concentration, in 3 of 4 groups given the 0.006% concentration, or in 1 of 4 groups given the 0.003% concentration. One or more swine were susceptible to reexposure to swine dysentery in both groups given the 0.012% concentration, in 1 group given the 0.006% concentration and in 1 group given the 0.003% concentration. Large spirochetes were observed in fecal smears from all exposed swine which developed either hemorrhagic or nonhemorrhagic diarrhea.