Ionophorous Anticoccidial Drugs in Coccidiosis Control

SummaryThe ionophorous anticoccidial drugs are fermentation products of various Streptomyces species, and although they are structurally related, they can have different effects on parasite and host. As coccidiosis control in fowls has again become a problem to the producer, it seems appropriate to evaluate the characteristics of the ionophorous drugs and the experiences obtained with them.After more than 10 years of use, these drugs are still market leaders in many countries and despite widespread use there have been few reports of resistance. Against turkey Eimeria, definite resistance to monensin has been found; it was possible to generate monensin resistance in the fourth generation by selection. This resistance was also found with lasalocid, narasin and salinomycin. In fowls, insensitivity of E. maxima isolates to monensin has been reported and decreasing efficacy of ionophorous drugs has also been noted in the field after several years of usage.