Efficacy of nequinate against thirteen strains of Eimeria tenella and the development of a nequinate-resistant strain

Chickens fed mash medicated with nequinate were protected against cecal coccidiosis (Eimeria tenella) infections initiated by a strain of the parasite that had no previous exposure to drugs and by 10 of 12 strains that were resistant to other coccidiostats. A strain of Eimeria tenella that was serially propagated in chickens fed nequinate became resistant to the drug. This strain concomitantly developed a cross resistance to buquinolate, decoquinate, nitrofurazone, and Trithiadol but not to 10 other coccidiostats. With 2 of these drugs, also substituted quinoline compounds, the cross resistance was reciprocal, i.e., strains resistant to them were tolerant to nequinate, and the nequinate-resistant strain was tolerant to them.