title: First report of amitraz and cypermethrin resistance in Rhipicephalus sanguineus sensu lato infesting dogs in Mexico.
abstract: Engorged female Rhipicephalus sanguineus sensu lato (Ixodida: Ixodidae) were collected from dogs in the state of Yucatán, Mexico. Fourteen tick populations were collected from dogs at seven veterinary clinics, four residential homes and three cattle farms. The larval immersion test was used in the progeny of collected adult females to test susceptibility to amitraz and cypermethrin. Dose-mortality regressions, 50% lethal concentrations (LC50), confidence intervals and slope were estimated by probit analysis. For amitraz, 12 tick populations (85.7%) were classified as resistant and low inter-population variation in the phenotypic level of resistance was evident [resistance ratios (RRs) at LC50: 1.0-13.0]. For cypermethrin, 12 tick populations (85.7%) were classified as resistant and substantial inter-population variation in the phenotypic level of resistance was evident (RRs at LC50: 1.0-104.0). Thus, amitraz resistance in R. sanguineus s.l. is common, but generally occurs at low levels; however, alarmingly high levels of cypermethrin resistance are present in R. sanguineus s.l. populations in dogs in Yucatán, Mexico. The intensive use of both acaricides to control ectoparasites on dogs is likely to lead to more serious resistance problems that may cause high levels of control failure in the future.
authors.affiliation: Departamento de Salud Animal y Medicina Preventiva, Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Mérida, Yucatán, Mexico.
authors.forename: R I
authors.initials: RI
authors.lastname: Rodriguez-Vivas
authors.affiliation: Departamento de Salud Animal y Medicina Preventiva, Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Mérida, Yucatán, Mexico.
authors.forename: M M
authors.initials: MM
authors.lastname: Ojeda-Chi
authors.affiliation: Departamento de Salud Animal y Medicina Preventiva, Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Mérida, Yucatán, Mexico.
authors.forename: I
authors.initials: I
authors.lastname: Trinidad-Martinez
authors.affiliation: Departamento de Salud Animal y Medicina Preventiva, Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Mérida, Yucatán, Mexico.
authors.forename: M E
authors.initials: ME
authors.lastname: Bolio-González
mesh_terms: D056810:Acaricides / Q000494:pharmacology*; D000818:Animals; D004283:Dog Diseases / Q000469:parasitology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D005260:Female; D007928:Lethal Dose 50; D008800:Mexico; D011722:Pyrethrins / Q000494:pharmacology*; D048508:Rhipicephalus sanguineus / Q000187:drug effects*; D013984:Tick Infestations / Q000469:parasitology / Q000662:veterinary*; D014052:Toluidines / Q000494:pharmacology*
chemical_list: D056810:Acaricides; D011722:Pyrethrins; D014052:Toluidines; C017160:cypermethrin; C014983:amitraz
keywords: Mexico; Rhipicephalus sanguineus sensu lato; amitraz; cypermethrin; dog