Study of the comparative efficacy of toltrazuril and diclazuril against ovine coccidiosis in housed lambs.

A blinded, controlled and randomised field study was conducted on a sheep farm with a known history of coccidiosis and a high prevalence mainly of the pathogenic coccidium Eimeria ovinoidalis. The efficacy of treatment with toltrazuril (Baycox 5% suspension) against natural infections with Eimeria crandallis and/or Eimeria ovinoidalis in housed lambs was investigated in comparison with diclazuril and untreated controls. Both drugs were administered either metaphylactically (i.e., in the prepatency of Eimeria spp.) or therapeutically (after onset of oocyst excretion). A total of 145 animals aged 1 to 5 days at the start of the study were included. Examination of faecal samples was performed every second day between days 13 and 49 of the study. The assessment of treatment efficacy was based mainly on total oocyst excretion and the number of E. crandallis and E. ovinoidalis oocysts (OPG) shed throughout the study. Oocyst excretion was reduced significantly in both groups treated with toltrazuril compared with the untreated control group and with both diclazuril-treated groups. The most prevalent and most severe diarrhoea was observed in the untreated control group. In this study, toltrazuril proved to be highly effective in controlling ovine coccidiosis both metaphylactically and therapeutically. The efficacy of toltrazuril was significantly higher than the efficacy of the control substance with regard to the duration and amount of oocyst excretion, both for the comparison of metaphylactic as well as therapeutic treatment.