Abstract: One Eimeria tenella isolated from Changzhou district of Jiangsu province was studied in a battery test for evaluating drug resistance against five commonly used anticoccidial drugs including sulfamethoxydiazine and diaveridine permix, sulfachloropyrazine sodium, toltrazuril, maduramycin and decoquinate. Suqin yellow chickens were randomly divided into seven groups of 10 each, which contained five medicated groups, one uninfected and unmedicated control, and one unmedicated and infected control. Chickens of medicated groups and infected control were prophylactic medicated and infected with sporulated oocysts at the age of 14 days. Drug resistance was assessed for each drug by calculating the relative oocyst production (ROP), reduction of lesion scores (RLS), percentage optimum anticoccidial activity (POAA) and anticoccidial index (ACI) . Results revealed that the E. tenella isolated from Changzhou district were sensitive to decoquinate, complete resistant to other four drugs. It suggested that in Changzhou district E. tenella was seriously resistant to drugs, decoquinate can be uesd, and the other drugs should be used reasonably or not be used at present.

Key words: Eimeria tenella; anticoccidial drug; drug resistance