Influence of level, timing and duration of ronidazole water medication on histomoniasis in turkeys.

Levels of 20, 30, 40, 60 and 120 parts per million (p.p.m.) of ronidazole in water were evaluated for therapeutic efficacy against histomoniasis. Three experiments were conducted with Broad Breasted Bronze and/or Large White poults four to nine weeks old. All poults except the unexposed controls were each given approximately 70 or 100 embryonated Heterakis gallinae ova containing Histomonas meleagridis. Ronidazole medications were administered during the following post-exposure periods: 7-13, 7-17, 10-17, 10-20, 10-23, 10-26, 14-20 and 14-24 days. Histomoniasis mortality and lesions were recorded in each experiment during a 28 or a 35-day post-exposure period. Level of ronidazole, timing and duration of medication significantly affected efficacy. Treatments involving 30 to 40 p.p.m. (or more) of ronidazole, initiated 10 days post-exposure and continued for at least 7-10 days were most effective.