This study investigated the efficacy of toltrazuril, including the resulting histopathological changes, in naturally occurring coccidiosis in Japanese quails. Eighty 12-week-old layers obtained from a commercial quail flock were divided into three experimental groups of 20 birds each (treated for 2 days) and one control (untreated) group. A parasitological analysis of the feces performed prior to the experiment revealed the presence of Eimeria tsunodai and Eimeria bateri oocysts (mixed infection in all birds). Group I received Baycox 2.5% at the dose recommended for broiler chickens – 7 mg/kg body weight per day (available 24 h). Group II received 14 mg/kg (available 24 h), and group III received 24.5 mg/kg (available for 8 h/24 h). Samples from the liver, kidney, duodenum, jejunum, ileum and cecum were collected for pathomorphological evaluation. The concentration of the toltrazuril used did not show total therapeutic effect. Only a dose of 24.5 mg/kg body weight led to total destruction of the coccidian in two Japanese quails. Toltrazuril supplementation generates toxic pathological changes in the liver and kidneys. The dose of toltrazuril established for chickens, as well as doses of 14 mg/kg and 24.5 mg/kg, were not completely effective in quails with E. tsunodai and E. bateri infection.

Key words: Coccidiosis, Eimeria tsunodai, Japanese quails, Toltrazuril