Laboratory Studies on the Anticoccidial Activity of Septamycin

was tested in vitro and in controlled battery experiments against various Eimeria species of the chicken. Complete inhibition of the development of E. tenella in chick kidney cell cultures occurred with a septamycin concentration of 0.01 jug./ml. Development beyond the trophozoite stage was completely blocked by this concentration added 3 h. after sporozoite inoculation; some host cell cytotoxicity was observed. Slight anticoccidial activity, based on reduced mortality and reduction of numbers of foci on the chorioallantoic membrane, was demonstrated at 0.01 mg. per egg in chick embryo infections; higher doses were embryotoxic. Septamycin showed good anticoccidial activity against severe infections with E. tenella in battery experiments: Dietary levels of 30—50 p.p.m. drug reduced mortality, while death and severe clinical symptoms were prevented by 60—120 p.p.m. septamycin. Improved weight gain and no mortality occurred with dosages of 25 and 50 p.p.m. septamycin when mixed infections were induced with 50 doses of Coccivac D ® per bird. Statistical analysis of data from a large scale experiment demonstrated that there was no significant difference of weight gain and feed conversions between E. brunetti-infected chicks treated with 50 p.p.m. septamycin and uninfected untreated controls. Poultry Science 56:1281-1288,197