In-vivo assessment of drug resistance in field isolates of Eimeria tenella

Abstract

Four field isolates of Eimeria tenella designated HI-1, HI-2, JI-1 and 11-2 isolated from severe outbreaks of caecal coccidiosis at broiler farms in some semi-arid regions of Haryana state lying in the sub-tropical belt of India, were assessed for the development of resistance to anticoccidials, viz. amprolium, clopidol, nitrofurazone + furazolidone and sodium sulphadimethylpyrimidine, The drugs were administered to the chicks 24 hr prior to oral challenge with 1 x 105 sporulated oocysts at 3 weeks of age. Infected unmedicated control (IUC) and un infected unmedicated control (UUC) were also maintained simultaneously. A relative anticoccidial index of each isolate of E. tenella against an anticoccidial was determined to ascertain the relative drug-resistance of coccidia. It was compared with another criterion of drugresistance, i.e. there was an at least 50% difference in the average dropping pan score (ADPS) of the chicks in IMCs and IUC. These criteria correlated in establishing resistance of all the 4 isolates to nitrofurazone+ furazolidone, some of the isolates to clopidol and sodium sulphadimethylpyrimidine and none of the isolates to amprolium.