Drug Responsiveness of Field Isolates of Chicken Coccidia

Coccidia were isolated from litter samples collected in poultry houses in Georgia and other southeastern states and from intestinal scrapings from chickens submitted to diagnostic laboratories. The most common species of coccidia encountered were E. tenella, E. acervulina, and E. maxima. Each of the 41 isolates was tested for sensitivity to eight commercial anticoccidial drugs. Most of the isolates were resistant to some of the drugs judged by the parameters of percent weight gain, percent lesion score reduction, and a sensitivity index score. There was a high frequency of resistance to clopidol, amprolium/ethopabate, nequinate, zoalene, and sulfaquinoxaline. A very small percentage of the isolates tested were resistant to nicarbazin, robenidine, or halofuginone.