title: Acaricide and ivermectin resistance in a field population of Rhipicephalus microplus (Acari: Ixodidae) collected from red deer (Cervus elaphus) in the Mexican tropics.
abstract: In the Neotropics the control of tick infestations in red deer (Cervus elaphus) is achieved primarily through the use of acaricides and macrocyclic lactones. In Mexico, resistance to one or multiple classes of acaricides has been reported in Rhipicephalus microplus infesting cattle, but information on acaricide susceptibility in R. microplus infesting red deer is lacking. In this study we report the level of resistance to different classes of acaricides and ivermectin in R. microplus collected from red deer in the Mexican tropics. Engorged R. microplus females were collected from a red deer farm in Yucatan, Mexico. The larval packet test was used to detect resistance to the organophosphates (OPs) chlorpyrifos and coumaphos, synthetic pyrethroids (SPs) cypermethrin and permethrin, and the phenylpyrazol, fipronil. Resistance to the formamidine amitraz (Am), and ivermectin was ascertained using the larval immersion test. Data were subjected to probit analysis to determine lethal concentrations and resistance ratios to kill 50% (RR50) and 99% (RR99) of the tick population under evaluation in relation to susceptible reference strains. Additionally, allele specific polymerase chain reaction was used to detect the sodium channel F1550I mutation associated with SP resistance in R. microplus. The R. microplus population from red deer in Yucatan showed very high resistance to the two SPs evaluated (RRs>72.2 for cypermethrin; RR for permethrin resistance was so high a dose-response curve was not possible). All individual larvae tested to detect the sodium channel F1550I mutation associated with SP resistance in R. microplus were homozygous. The same tick population showed different levels of resistance to OPs (chlorpyrifos: RR50=1.55, RR99=0.63; coumaphos: RR50=6.8, RR99=5.9), fipronil (RR50=1.8, RR99=0.9), and amitraz (RR50=2.3, RR99=4.4). Resistance to ivermectin was regarded as moderate (RR50=7.1, RR99=5.0). This is the first report of R. microplus ticks collected from red deer in Mexico with different levels of resistance to four acaricide groups and ivermectin.
authors.affiliation: Cuerpo Académico de Salud Animal, Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Km. 15.5 Carretera Mérida-Xmatkuil, CP. 97100 Mérida, Yucatán, Mexico. Electronic address: rvivas@uady.mx.
authors.forename: R I
authors.initials: RI
authors.lastname: Rodríguez-Vivas
authors.affiliation: USDA, ARS, Cattle Fever Tick Research Laboratory, 22675 North Moorefield Road, Building 6419, Edinburg, TX 78541, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Miller
authors.affiliation: Cuerpo Académico de Salud Animal, Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Km. 15.5 Carretera Mérida-Xmatkuil, CP. 97100 Mérida, Yucatán, Mexico.
authors.forename: M M
authors.initials: MM
authors.lastname: Ojeda-Chi
authors.affiliation: Cuerpo Académico de Salud Animal, Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Km. 15.5 Carretera Mérida-Xmatkuil, CP. 97100 Mérida, Yucatán, Mexico.
authors.forename: J A
authors.initials: JA
authors.lastname: Rosado-Aguilar
authors.affiliation: Cuerpo Académico de Salud Animal, Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Km. 15.5 Carretera Mérida-Xmatkuil, CP. 97100 Mérida, Yucatán, Mexico.
authors.forename: I C
authors.initials: IC
authors.lastname: Trinidad-Martínez
authors.affiliation: USDA, ARS, Knipling-Bushland U.S. Livestock Insects Research Laboratory, 2700 Fredericksburg Road, Kerrville, TX 78028, USA.
authors.forename: A A
authors.initials: AA
authors.lastname: Pérez de León
mesh_terms: D056810:Acaricides / Q000494:pharmacology*; D000483:Alleles; D000818:Animals; D000977:Antiparasitic Agents / Q000494:pharmacology*; D003670:Deer / Q000469:parasitology*; D007305:Insecticide Resistance / Q000235:genetics; D007559:Ivermectin / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects; D008800:Mexico; D048494:Rhipicephalus / Q000187:drug effects* / Q000235:genetics; D013984:Tick Infestations / Q000469:parasitology; D014329:Tropical Climate
chemical_list: D056810:Acaricides; D000977:Antiparasitic Agents; D007559:Ivermectin
keywords: Acaricide susceptibility; Diversified livestock production; Ivermectin resistance; Mexico; Red deer (Cervus elaphus); Rhipicephalus microplus