Sustainable coccidiosis control implications based on susceptibility of European Eimeria field isolates to narasin + nicarbazin from farms using anticoccidial medication or coccidial vaccines

Twenty-seven Eimeria spp. field isolates from 10 European countries were examined for sensitivity to the anticoccidial combination narasin + nicarbazin. Twenty-three of the samples were collected from farms using anticoccidial medication programs, and 4 of the samples were collected from farms using coccidiosis vaccination as the exclusive coccidiosis control method. Ninety-five percent of the isolates collected from farms using in-feed anticoccidial medication demonstrated poor sensitivity to narasin + nicarbazin. By contrast, 100% of the isolates collected from the coccidiosis vaccinated farms demonstrated good sensitivity, with a highly significant reduction in oocyst output when the isolates from the vaccinated farms were fed narasin + nicarbazin. As sensitivity of in-feed anticoccidials declines, a combination of the use of vaccine and anticoccidial strategies may be required for sustainable coccidiosis control.