Haemonchus placei, Cooperia punctata and Oesophagostomum radiatum resistant to ivermectin pour-on 500mcg[kg.sup.-1] in cattle from Brazil/Resistencia de Haemonchus placei, Cooperia punctata e Oesophagostomum radiatum a ivermectina pour-on a 500mcg[kg.sup.-1] em rebanhos bovinos no Brasil

• Published in: Ciência rural Vol. 44; no. 5; p. 847
• Main Authors: Lopes, Welber Daniel Zanetti, Felippelli, Gustavo, Teixeira, Weslen Fabricio Pires, Cruz, Breno Cayeiro, Maciel, Willian Giquelin, Buzzulini, Carolina, de Matos, Lucas Vinicius Shigaki, Gomes, Lucas Vinicius Costa, Pereira, Joao Carlos Melo, Favero, Flavia Carolina, de Oliveira, Gilson Pereira, da Costa, Alvimar Jose
• Format: Journal Article
• Language: Spanish
• Published: Universidade Federal de Santa Maria 01-05-2014
• Subjects: Cattle; Ivermectin; Lactones; Roundworms
• ISSN: 0103-8478

The broad spectrum of endectocides and the easy use mode of their pour-on formulations are factors that have stimulated a higher frequency of use these drugs in cattle. In this study was evaluated the efficacy of ivermectin pour-on using the dose of 500mcg[kg.sup.-1], against nematodes in naturally infected cattle from different herds. Twelve calves were brought from each of the four farms selected. All the 48 calves used showed mean of eggs per gram of feces (EPG) greater than 500 considering three consecutive counts. Subsequently, animals from each herd were divided into two groups of six animals each, one treated pour-on with ivermectin 500mcg[kg.sup.-1] and other kept as untreated control. Calves were euthanized 14 days after treatment for counting the endoparasites. Ivermectin showed null effect against H. placei in all the herds evaluated. The drug was also ineffective against C. punctata in the herds from Jaboticabal, SP and Formiga, MG, and reached efficacy of 75.8% and 58.4% in herds from Sao Jose do Rio Pardo, SP and Sao Sebastiao do Paraiso, MG, respectively. Efficacies of 94.2% (Jaboticabal), 0.0% (Sao Jose do Rio Pardo), 94.2% (Formiga) and 39.2% (Sao Sebastiao do Paraiso) were detectedagainstO. radiatum. Based on these results obtained on the present study, the four populations of Haemonchus placei and Cooperia punctata evaluated were resistant to ivermectin pour-on using a dose of 500mcg[kg.sup.-1]. Ivermectin-resistant strains of Oesophagostomum radiatum were found in two of the four herds evaluated. Key words: gastrointestinal nematodes, macrocyclic lactones, multiple resistance, ruminants, topically. O amplo espectro de acao dos endectocidas e a praticidade de aplicacao das suas formulacoes pour-on sao fatores que tem estimulado uma maior frequencia de utilizacao destes produtos na criacao de bovinos. Neste estudo, avaliouse a eficacia anti-helmintica da ivermectina, administrada via pour-on, 500mcg[kg.sup.-1], contra nematodeos de bovinos provenientes de diferentes rebanhos. Foram adquiridos 12 bezerros de cada um dos quatro rebanhos selecionados. Todos os 48 bezerros utilizados apresentavam medias de ovos por grama de fezes (OPG) maiores que 500, considerando-se tres contagens consecutivas. Na sequencia, os animais de cada rebanho foram divididos em dois grupos de seis bovinos cada, sendo um tratado com ivermectina 500mcg[kg.sup.-1] via pour-on e outro mantido como controle. Quatorze dias depois do tratamento, os bovinos foram submetidos a eutanasia para contagem de endoparasitas. A ivermectina demonstrou resultados nulos de eficacia contra H. placei nos quatro rebanhos. Contra C. punctata, tal formulacao teve eficacia nula nos rebanhos provenientes de Jaboticabal, SP, e de Formiga, MG, e eficacias de 75,8% e 58,4% nos rebanhos provenientes de Sao Jose do Rio Pardo, SP, e de Sao Sebastiao do Paraiso,MG, respectivamente. Valores de eficacia de 94,2% (Jaboticabal), 0,0% (Sao Jose do Rio Pardo), 94,2% (Formiga) e 39,2% (Sao Sebastiao do Paraiso) foram detectados contra O. radiatum. Com base nos resultados encontrados, pode-se concluir que as quatro populacoes de Haemonchus placei e de Cooperia punctata avaliadas foram resistentes a ivermectina, administrada via pour-on, 500mcg[kg.sup.-1]. Foram observadas cepas de Oesophagostomum radiatum resistentes a ivermectina em dois dos quatro rebanhos testados. Palavras-chave: nematodeosgastrintestinais, lactonas macrociclicas, resistencia multipla, ruminantes, via topica.