title: Efficacy of major anthelmintics for reduction of fecal shedding of strongyle-type eggs in horses in the Mid-Atlantic region of the United States.
abstract: In the last decade there have been numerous reports of anthelmintic resistant cyathostomins in many parts of the world. The objective of the present study was to evaluate the efficacy of the commercially available anthelmintics against cyathostomin egg shedding in the Mid-Atlantic region of the United States. A total of 989 horses from 67 different farms located in southeastern Pennsylvania, northern Delaware, and northeastern Maryland were treated with fenbendazole, oxibendazole, pyrantel pamoate, ivermectin, or moxidectin at their recommended dosages. Fecal egg count reduction testing was used to determine the efficacy of each anthelmintic on those horses with fecal egg counts of ≥ 200 eggs per gram on the day of treatment (272 horses). Decreased efficacy (reduction of strongyle-type fecal egg counts by less than 90%) was found for fenbendazole, oxibendazole, and pyrantel pamoate, with only 6%, 21% and 43% of horses showing reductions of greater than 90%, respectively. The macrocyclic lactones showed high efficacy in all horses sampled in this study. The decreased anthelmintic efficacy detected in this study adds further evidence for the existence of resistant cyathostomins throughout much of the eastern United States. Findings from this study can be used to create a more sustainable approach for parasite control programs.
authors.affiliation: Department of Clinical Studies, New Bolton Center, University of Pennsylvania, Kennett Square, PA, USA. Electronic address: meagans@vet.upenn.edu.
authors.forename: M A
authors.initials: MA
authors.lastname: Smith
authors.affiliation: Department of Pathobiology, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Nolan
authors.affiliation: Department of Statistics, West Chester University, West Chester, PA, USA.
authors.forename: R
authors.initials: R
authors.lastname: Rieger
authors.affiliation: Department of Clinical Studies, New Bolton Center, University of Pennsylvania, Kennett Square, PA, USA.
authors.forename: H
authors.initials: H
authors.lastname: Aceto
authors.affiliation: Department of Clinical Studies, New Bolton Center, University of Pennsylvania, Kennett Square, PA, USA.
authors.forename: D G
authors.initials: DG
authors.lastname: Levine
authors.affiliation: Department of Clinical Studies, New Bolton Center, University of Pennsylvania, Kennett Square, PA, USA.
authors.forename: R
authors.initials: R
authors.lastname: Nolen-Walston
authors.affiliation: Department of Clinical Studies, New Bolton Center, University of Pennsylvania, Kennett Square, PA, USA.
authors.forename: B I
authors.initials: BI
authors.lastname: Smith
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use*; D004351:Drug Resistance; D005243:Feces / Q000469:parasitology; D006376:Helminths / Q000187:drug effects; D006734:Horse Diseases / Q000188:drug therapy / Q000469:parasitology*; D006736:Horses; D010063:Ovum / Q000187:drug effects; D010270:Parasite Egg Count / Q000662:veterinary*; D014481:United States / Q000453:epidemiology
chemical_list: D000871:Anthelmintics
keywords: Equine; Fecal egg count reduction test; Fenbendazole; Ivermectin; Moxidectin; Oxibendazole; Pyrantel pamoate; Small strongyle