title: Susceptibility of Rhipicephalus (Boophilus) microplus to fluazuron (2.5mg/kg) and a combination of novaluron (2.0mg/kg)+eprinomectin (0.36mg/kg) in field studies in Brazil.
abstract: The present study aimed to determine the susceptibility of 32 R. (B.) microplus populations from Southeast, Midwest and South regions of Brazil, to fluazuron (2.5mg/kg), administered topically (pour-on). Additionally, five populations (Southeast and Midwest regions) of the southern cattle tick were evaluated using in vivo field studies, regarding their susceptibility to a new combination of novaluron (2.0mg/kg)+eprinomectin (0.36mg/kg), administered subcutaneously, compared with two positive controls (fluazuron 2.5mg/kg and eprinomectin 0.5mg/kg), both administered topically (pour-on). Selected bovines were allocated to treatment groups on day 0, and block formation was based on arithmetic means of female ticks (4.5-8.0mm long) counted on three consecutive days (-3, -2 and -1). To evaluate therapeutic and residual efficacies of these formulations, tick counts (females ranging from 4.5 to 8.0mm long) were performed on days 3, 7 and 14 post-treatment, continuing on a weekly basis until the end of each experiment. Results obtained throughout this study, utilizing field efficacy trials, allowed us to conclude that four R. (B.) microplus populations (including two in the Southeast and two in the Midwest regions) could be diagnosed as resistant, or with low susceptibility, to fluazuron (2.5mg/kg). Such fact was detected in farms where owners applied products containing this active component on cattle for at least five years, with treatment intervals of 30-55days during the rainy season. Nonetheless, in vitro studies should be performed in order to reinforce in vivo results obtained on the present study. Regarding efficacy indexes obtained by the association of eprinomectin and the novel molecule novaluron against R. (B.) microplus, none of the trials managed to obtain efficacies superior to 48%. Such results, allied to data obtained by different researchers and previously published in literature, reinforce the perception that maybe these formulations containing novaluron, in the administered dosages and treatment routes, may not be effective tools for controlling R. (B.) microplus. However, future studies must be conducted in order to support such hypothesis. Additionally, all five R. (B.) microplus populations were diagnosed as resistant, or with low susceptibility, to eprinomectin (0.5mg/kg) as well. Even though fluazuron, administered topically (pour on), is still an excellent active principle to be used against R. (B.) microplus, resistance management strategies should be quickly implemented in order to keep selection pressure in Brazil at a minimum level for this compound.
authors.affiliation: CPPAR - Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Jaboticabal Campus, Access Route Prof. Paulo Donato Castellane, 14884-900, Jaboticabal, São Paulo, 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, Jaboticabal Campus, Access Route Prof. Paulo Donato Castellane, 14884-900, Jaboticabal, São Paulo, Brazil; Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás (IPTSP/EVZ/UFG), 74605-050, Goiânia, Goiás, Brazil. Electronic address: wdzlopes@hotmail.com.
authors.forename: Welber Daniel Zanetti
authors.initials: WDZ
authors.lastname: Lopes
authors.affiliation: CPPAR - Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Jaboticabal Campus, Access Route Prof. Paulo Donato Castellane, 14884-900, Jaboticabal, São Paulo, Brazil.
authors.forename: Lucas Vinicius Costa
authors.initials: LVC
authors.lastname: Gomes
authors.affiliation: CPPAR - Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Jaboticabal Campus, Access Route Prof. Paulo Donato Castellane, 14884-900, Jaboticabal, São Paulo, 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, Jaboticabal Campus, Access Route Prof. Paulo Donato Castellane, 14884-900, Jaboticabal, São Paulo, Brazil.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Felippelli
authors.affiliation: CPPAR - Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Jaboticabal Campus, Access Route Prof. Paulo Donato Castellane, 14884-900, Jaboticabal, São Paulo, Brazil.
authors.forename: Isabella Barbosa Dos
authors.initials: IBD
authors.lastname: Santos
authors.affiliation: Universidade Federal do Mato Grosso do Sul (UFMS), Campo Grande, Mato Grosso do Sul, Brazil.
authors.forename: Fernando de Almeida
authors.initials: FA
authors.lastname: Borges
authors.affiliation: Universidade Estadual de Maringá, Umuarama Regional Campus, Paraná, Brazil.
authors.forename: Walter Antonio
authors.initials: WA
authors.lastname: Gonçalves
authors.affiliation: Universidade Federal de Goiás, Regional de Jataí, Brazil.
authors.forename: Alexandre Braga
authors.initials: AB
authors.lastname: Scarpa
authors.affiliation: Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás (IPTSP/EVZ/UFG), 74605-050, Goiânia, Goiás, Brazil.
authors.forename: João Eduardo
authors.initials: JE
authors.lastname: Nicaretta
authors.affiliation: Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás (IPTSP/EVZ/UFG), 74605-050, Goiânia, Goiás, Brazil.
authors.forename: Thiago Souza Azeredo
authors.initials: TSA
authors.lastname: Bastos
authors.affiliation: CPPAR - Animal Health Research Center, Faculdade de Ciências Agrárias e Veterinárias, UNESP, Jaboticabal Campus, Access Route Prof. Paulo Donato Castellane, 14884-900, Jaboticabal, São Paulo, Brazil.
authors.forename: Alvimar José
authors.initials: AJ
authors.lastname: da Costa
mesh_terms: D056810:Acaricides; D000818:Animals; D001938:Brazil; D002417:Cattle; D002418:Cattle Diseases / Q000469:parasitology / Q000517:prevention & control*; D004351:Drug Resistance; D005260:Female; D007559:Ivermectin / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D048494:Rhipicephalus; D013984:Tick Infestations / Q000469:parasitology / Q000517:prevention & control / Q000662:veterinary*
chemical_list: D056810:Acaricides; D010671:Phenylurea Compounds; D007559:Ivermectin; C101434:eprinomectin; C104929:fluazuron; C471805:novaluron
keywords: Benzoylphenyl urea; Cattle; Macrocyclic lactone; Resistance; Ticks