title: Rhipicephalus (Boophilus) microplus in the western-central region of Rio Grande do Sul, Brazil: multiresistant tick.
abstract: The aim of the present study was to assess the acaricide resistance of tick populations in the western-central region of Rio Grande do Sul (Brazil), which has not previously been reported. Fifty-four cattle farms were visited and specimens of Rhipicephalus (Boophilus) microplus were collected and subjected to the adult immersion test, using nine commercial acaricides in the amidine, pyrethroid and organophosphate groups. Climatic data, including monthly precipitation, were recorded. The results from the present study demonstrated that seven of the acaricides analyzed presented mean efficacy values of less than 95%, with large differences among the products tested. Nine of them exhibited satisfactory and unsatisfactory acaricide results on at least one farm. In conclusion, the farms located in the western-central region of Rio Grande do Sul, Brazil, exhibited populations of R. (Boophilus) microplus with variable degrees of susceptibility to different acaricides, thus suggesting that resistance to the active compounds exists. It is suggested that treatment protocols should be implemented at the beginning of winter and summer, using the acaricides that showed efficacy in the adult immersion test.
authors.affiliation: Laboratório de Doenças Parasitárias, Departamento de Medicina Veterinária Preventiva, Universidade Federal de Santa Maria ? UFSM, Santa Maria, RS, Brasil.
authors.forename: Fabrício Amadori
authors.initials: FA
authors.lastname: Machado
authors.affiliation: Clínica de Medicina de Ruminantes, Departamento de Clínica de Grandes Animais, Universidade Federal de Santa Maria ? UFSM, Santa Maria, RS, Brasil.
authors.forename: Felipe Lamberti
authors.initials: FL
authors.lastname: Pivoto
authors.affiliation: Laboratório de Doenças Parasitárias, Departamento de Medicina Veterinária Preventiva, Universidade Federal de Santa Maria ? UFSM, Santa Maria, RS, Brasil.
authors.forename: Maiara Sanitá Tafner
authors.initials: MS
authors.lastname: Ferreira
authors.affiliation: Santa Maria, Santa Maria, RS, Brasil.
authors.forename: Fabiano de Vargas
authors.initials: Fde V
authors.lastname: Gregorio
authors.affiliation: Laboratório de Doenças Parasitárias, Departamento de Medicina Veterinária Preventiva, Universidade Federal de Santa Maria ? UFSM, Santa Maria, RS, Brasil.
authors.forename: Fernanda Silveira Flores
authors.initials: FS
authors.lastname: Vogel
authors.affiliation: Laboratório de Doenças Parasitárias, Departamento de Medicina Veterinária Preventiva, Universidade Federal de Santa Maria ? UFSM, Santa Maria, RS, Brasil.
authors.forename: Luís Antônio
authors.initials: LA
authors.lastname: Sangioni
mesh_terms: D000818:Animals; D001938:Brazil; D002417:Cattle / Q000469:parasitology*; D018432:Drug Resistance, Multiple; D005260:Female; D048494:Rhipicephalus / Q000187:drug effects* / Q000502:physiology; D012621:Seasons