Characteristics of the anticoccidial activity of 6-azauracil.

The characteristics of anticoccidial activities of 6-azauracil (AzU) were investigated in the battery trials utilizing the White Leghorn cockerels, which were infected with Eimeria tenella, E. necatrix, E. acervulina, E. maxima and/or E. brunetti. AzU was mixed into the basal starter feed and fed ad libitum to the birds from 1 day before the inoculation of oocysts to the time of necropsy. AzU showed remarkable anticoccidial activity against E. tenella and E. necatrix infections at doses of 1,000 ppm in feed or more, and fairly good effect against E. acervulina infection at the dose of 4,000 ppm in feed. Inadequate effect against E. maxima infection and null in effect against E. brunetti at the dose of 4,000 ppm were resulted for this drug. The effect of 6-azauridine, ribonucleoside of AzU against E. tenella and E. necatrix infections at 1,000 ppm was tested and revealed negative results. In the test with AzU-resistant line of E. tenella, cross resistance was confirmed between AzU and emimycin riboside, a uridine analogue. Activity of AzU was studied in vitro against E. tenella in chick kidney cells. AzU inhibited the development of the first- and second-generation schizonts at 100-200 ppm in the medium. Degenerated parasites were observed.