The efficacy of monensin at concentrations of 60 and 100 ppm was evaluated against 22 isolates not exposed to monensin and 16 monensin-exposed field isolates of coccidia obtained from US and Canadian turkey flocks, respectively. Isolates not previously exposed to monensin were effectively controlled by monensin. However, 7 monensin-resistant isolates (predominantly Eimeria meleagrimitis) were independently isolated from turkey flocks in Ontario, Canada where monensin was being used as an anticoccidial. Subsequent sensitivity evaluations of two of these isolates revealed cross-resistance to lasolocid, narasin, and salinomycin. Evaluation of the stability of monensin resistance in one isolate suggested that monensin sensitivity was not restored after 10 generations of relaxed selection. Although the extent of monensin resistance among field isolates of turkey coccidia is unknown, these results provide the first unequivocal characterization of monensin resistance in field isolates of coccidia. Contrarily, after more than eight years of intensive use of monensin as an anticoccidial in US broiler production facilities, this type of resistance to the polyether antibiotic anticoccidials has not been encountered in chicken coccidia.
The discovery of monensin-resistant field isolates of Eimeria meleagrimitis prompted an investigation of the ability of this parasite to develop monensin resistance in a laboratory selection experiment. A strain derived from a monensin-sensitive parent strain was intentionally selected for monensin resistance by propagation in monensin medicated turkeys in isolation, while the monensin-sensitive parent strain from which it was derived was cryogenically maintained as a genetic control. Comparison of the monensin sensitivity of the selected and parent strains demonstrated monensin resistance development in the selected strain by the fourth generation of selection. This is the first reported experimental development of monensin-resistant coccidia and suggests that unlike chicken coccidia, the turkey coccidium E. meleagrimitis possesses the ability to readily develop resistance to the polyether antibiotic anticoccidials under the appropriate conditions of drug exposure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.