In July 1971, the polyether ionophorous
antibiotic monensin was introduced in the United States for the control of
coccidiosis in poultry. At that time, prospects for new
anticoccidial agents were not good.
Amprolium had enjoyed several years of use, but many other compounds had been abandoned as resistance to them developed. After the introduction of
monensin, most commercial broilers were medicated with the
drug and it is still widely used for this purpose today. Apart from in poultry,
monensin is also used to control
coccidiosis in game birds, sheep, and cattle. Indeed, more animals have been medicated with
ionophores, such as
monensin, for control of disease than any other medicinal agents in the history of veterinary medicine. In this review, we discuss the discovery, mode of action, and efficacy of
monensin, together with matters of importance to the poultry industry such as commercial use, drug resistance, toxicity, pharmacology and residues, host immunity to
coccidiosis, and effects in other avian species.