Abstract
A field survey on the drug resistance of chicken coccidia found in Japanesebroilers was performed by the chicken inoculation test with 30 fecal samples collectedfrom 29 prefectures in June, 1973. A strain was judged as a resistant one when it showedoocyst production with or without symptoms of coccidiosis in an experimental birdmedicated with twice as much as tlae recommended dose of a coccidiostat.As a result, 93% and 97% of the strains of Eimeria acervulina studied were foundresistant to clopidol and decoquinate, respectively. A considerable percentage of thestrains of E. tenella and E. necatrix studied were found resistant to amprolium, clopidol anddecoquinate. Only a small percentage of these strains was resistant to sulfadimethoxine.Moreover, multiple drug-resistant strains were found very commonly in E. tetzella, E.necatrix. E. maxintct and E. acervulina.Distribution of the resistant coccidia was variable over seven geographical districts inJapan.A large number of E. acervulina strains were found resistant to eight times the recom-mended dose of amprolium and/or decoquinate. Many strains of E. tenella and E. necatrixwere highly resistant to amprolium and decoquinate. Development of resistance to clopi-dol was variable among these species.
