Development of resistance to quinoline coccidiostats under field and laboratory conditions

Methyl 7-diethylamino-4-hydroxy-6-n-propylquinoline-3-carboxylate, amquinolate, initially showed great promise as a broad-spectrum anticoccidial agent in extensive evaluation studies against 120 laboratory and field strains of coccidia. Subsequently, further tests were conducted with 12 field strains obtained from commercial poultry farms where a related quinoline coccidiostat reportedly had failed to control coccidiosis. The 12 strains were resistant to four new quinoline coccidiostats: amquinolate, buquinolate, M&B 15497, and methyl benzoquate. Results of laboratory tests designed to induce resistance indicated that strains of Eimeria tenella, Eimeria maxima, Eimeria brunetti, and Eimeria acervulina acquired definite tolerance after only four to eight serial exposures to amquinolate.