title: Molecular survey of pyrethroid resistance mechanisms in Mexican field populations of Rhipicephalus (Boophilus) microplus.
abstract: Susceptibility to synthetic pyrethroids (SP s) and the role of two major resistance mechanisms were evaluated in Mexican Rhipicephalus microplus tick populations. Larval packet test (LPT), knock-down (kdr) PCR allele-specific assay (PASA) and esterase activity assays were conducted in tick populations for cypermethrin, flumethrin and deltamethrin. Esterase activity did not have a significant correlation with SP s resistance. However a significant correlation (p < 0.01) was found between the presence of the sodium channel mutation, and resistance to SP s as measured by PASA and LPT respectively. Just over half the populations (16/28) were cross-resistant to flumethrin, deltamethrin and cypermethrine, 21.4% of the samples (6/28) were susceptible to all of the three pyrethroids 10.7 of the samples (3/28) were resistant to flumethrin, 3.4 of the samples (1/28) were resistant to deltamethrin only and 7.1% (2/28) were resistant to flumethrin and deltamethrin. The presence of the kdr mutation correlates with resistance to the SP s as a class. Target site insensitivity is the major mechanism of resistance to SP s in Mexican R. microplus field strains, involving the presence of a sodium channel mutation, however, esterase-based, other mutations or combination of mechanisms can also occur.
authors: Centro Nacional de Investigacion Disciplinaria en Parasitologia Veterinaria, Carr. Fed. Cuernavaca-Cuautla # 8534. Col. Progreso, Jiutepec C.P. 62550, Morelos, Mexico. rockdrig@yahoo.com.mx
authors: Rodrigo
authors: R
authors: Rosario-Cruz
authors: Felix D
authors: FD
authors: Guerrero
authors: Robert J
authors: RJ
authors: Miller
authors: Roger Ivan
authors: RI
authors: Rodriguez-Vivas
authors: Mary
authors: M
authors: Tijerina
authors: Delia Ines
authors: DI
authors: Dominguez-Garcia
authors: Ruben
authors: R
authors: Hernandez-Ortiz
authors: Anthony J
authors: AJ
authors: Cornel
authors: Rory D
authors: RD
authors: McAbee
authors: Miguel Angel
authors: MA
authors: Alonso-Diaz
mesh_terms: D000818:Animals; D002417:Cattle; D004351:Drug Resistance; D004950:Esterases / Q000378:metabolism; D005260:Female; D055785:Gene Knockdown Techniques; D007306:Insecticides / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects; D008800:Mexico; D020125:Mutation, Missense; D011722:Pyrethrins / Q000494:pharmacology*; D048494:Rhipicephalus / Q000187:drug effects* / Q000235:genetics*; D015222:Sodium Channels / Q000235:genetics; D016019:Survival Analysis
chemical_list: D007306:Insecticides; D011722:Pyrethrins; D015222:Sodium Channels; D004950:Esterases