title: Nematode resistance to ivermectin (630 and 700μg/kg) in cattle from the Southeast and South of Brazil.
abstract: Two high doses of ivermectin (630μg/kg and 700μg/kg) that are sold commercially in Brazil were evaluated in dose-and-slaughter trials with 144 naturally nematode-infected cattle from eight regions within the states of Minas Gerias, São Paulo and Rio Grande do Sul in Brazil. Treatment groups were based on fecal egg counts 1, 2, and 3days before treatment; all animals studied had a minimum egg count of at least 500 eggs per gram of feces (EPG). Post-mortem analyses were conducted on day 14. The highest levels of resistance to ivermectin were found for Haemonchus placei, Cooperia punctata and Oesophagostomum radiatum; all populations of H. placei were resistant to the 630μg/kg dose, and 67% were resistant to 700μg/kg; 86% of C. punctata were resistant to the 630μg/kg dose, and 33% were resistant to 700μg/kg. A combined analysis revealed that 57% of O. radiatum were resistant to the lower dose of ivermectin. H. placei, C. punctata and O. radiatum, in order, were the nematode populations with the highest indices of resistance, whereas Trichostrongylus axei was the most susceptible to 630 and 700μg/kg dosages of ivermectin. The results of helminthic resistance to ivermectin for different populations of H. placei and C. punctata described in the present study support previous literature data, in which a small decrease in the average parasitic burden of C. punctata and a consequent increase of H. placei were observed in cattle from the Southeast, South and Center-West regions of Brazil.
authors.affiliation: CPPAR, Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de Acesso Prof. Paulo Donatto Castellani, s/n CEP:14884-900, Jaboticabal, São Paulo-Brasil, Brazil.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Felippelli
authors.affiliation: CPPAR, Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de Acesso Prof. Paulo Donatto Castellani, s/n CEP:14884-900, Jaboticabal, São Paulo-Brasil, Brazil. Electronic address: wdzlopes@hotmail.com.
authors.forename: Welber Daniel Zanetti
authors.initials: WD
authors.lastname: Lopes
authors.affiliation: CPPAR, Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de Acesso Prof. Paulo Donatto Castellani, s/n CEP:14884-900, Jaboticabal, São Paulo-Brasil, Brazil.
authors.forename: Breno Cayeiro
authors.initials: BC
authors.lastname: Cruz
authors.affiliation: CPPAR, Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de Acesso Prof. Paulo Donatto Castellani, s/n CEP:14884-900, Jaboticabal, São Paulo-Brasil, Brazil.
authors.forename: Weslen Fabricio Pires
authors.initials: WF
authors.lastname: Teixeira
authors.affiliation: CPPAR, Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de Acesso Prof. Paulo Donatto Castellani, s/n CEP:14884-900, Jaboticabal, São Paulo-Brasil, Brazil.
authors.forename: Willian Giquelin
authors.initials: WG
authors.lastname: Maciel
authors.affiliation: CPPAR, Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de Acesso Prof. Paulo Donatto Castellani, s/n CEP:14884-900, Jaboticabal, São Paulo-Brasil, Brazil.
authors.forename: Flávia Carolina
authors.initials: FC
authors.lastname: Fávero
authors.affiliation: CPPAR, Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de Acesso Prof. Paulo Donatto Castellani, s/n CEP:14884-900, Jaboticabal, São Paulo-Brasil, Brazil.
authors.forename: Carolina
authors.initials: C
authors.lastname: Buzzulini
authors.affiliation: CPPAR, Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de Acesso Prof. Paulo Donatto Castellani, s/n CEP:14884-900, Jaboticabal, São Paulo-Brasil, Brazil.
authors.forename: Claudio
authors.initials: C
authors.lastname: Sakamoto
authors.affiliation: CPPAR, Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de Acesso Prof. Paulo Donatto Castellani, s/n CEP:14884-900, Jaboticabal, São Paulo-Brasil, Brazil; UNICASTELO - Universidade Camilo Castelo Branco, Brazil.
authors.forename: Vando Edésio
authors.initials: VE
authors.lastname: Soares
authors.affiliation: CPPAR, Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de Acesso Prof. Paulo Donatto Castellani, s/n CEP:14884-900, Jaboticabal, São Paulo-Brasil, Brazil.
authors.forename: Lucas Vinicius Costa
authors.initials: LV
authors.lastname: Gomes
authors.affiliation: CPPAR, Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de Acesso Prof. Paulo Donatto Castellani, s/n CEP:14884-900, Jaboticabal, São Paulo-Brasil, Brazil.
authors.forename: Gilson Pereira
authors.initials: GP
authors.lastname: de Oliveira
authors.affiliation: CPPAR, Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Via de Acesso Prof. Paulo Donatto Castellani, s/n CEP:14884-900, Jaboticabal, São Paulo-Brasil, Brazil.
authors.forename: Alvimar José
authors.initials: AJ
authors.lastname: da Costa
mesh_terms: D000818:Animals; D000977:Antiparasitic Agents / Q000494:pharmacology*; D001938:Brazil; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy / Q000469:parasitology*; D004351:Drug Resistance; D005243:Feces / Q000469:parasitology; D007559:Ivermectin / Q000494:pharmacology*; D008297:Male; D010270:Parasite Egg Count / Q000662:veterinary; D017183:Strongylida / Q000187:drug effects* / Q000302:isolation & purification; D017206:Strongylida Infections / Q000188:drug therapy / Q000469:parasitology*; D016896:Treatment Outcome
chemical_list: D000977:Antiparasitic Agents; D007559:Ivermectin
keywords: Bovines; Helminths; High concentration; Ivermectin; Resistance