Study of resistance against some ionophores in Eimeria tenella field isolates

Three Eimeria tenella field isolates from Gurgaon district of Haryana (nort h India) were studied in a battery test for evaluating drug resistance agai nst two currently used ionophores; maduramicin (5 ppm) and salinomycin (60 ppm). Broiler birds (Ross strain) were infected with 10(5) sporulated oocys ts each at the age of 2 weeks and prophylactic medication commenced 2 days prior to infection. Drug resistance was assessed by calculating the global index for individual ionophore compounds based on weight gain, feed convers ion ratio, oocyst index, lesion score and mortality. Present studies reveal ed no resistance of the ionophores in any of the field isolates. Both the d rugs showed varying degree of efficacy, e.g. maduramicin exhibited limited efficacy against all the three field isolates, whereas salinomycin showed l imited efficacy against Gurgaon isolate (GrI)-I, good efficacy against GrI- II and partial resistance against GrI-III. (C) 2001 Elsevier Science B.V. A ll rights reserved.