title: Wide spread cross resistance to pyrethroids in Aedes aegypti (Diptera: Culicidae) from Veracruz state Mexico.
abstract: Seven F1 strains of Aedes aegypti (L.) were evaluated by bottle bioassay for resistance to the pyrethroids d-phenothrin, permethrin, deltamethrin, lambda-cyalothrin, bifenthrin, cypermethrin, alpha-cypermethrin, and z-cypermethrin. The New Orleans strain was used as a susceptible control. Mortality rates after a 1 h exposure and after a 24 h recovery period were determined. The resistance ratio between the 50% knockdown values (RR(KC50)) of the F1 and New Orleans strains indicated high levels of knockdown resistance. The RR(KC50) with alpha-cypermethrin varied from 10 to 100 among strains indicating high levels of knockdown resistance. Most of the strains had moderate resistance to d-phenothrin. Significant but much lower levels of resistance were detected for lambda-cyalothrin, permethrin, and cypermethrin. For zeta-cypermethrin and bifenthrin, only one strain exhibited resistance with RR(KC50) values of 10- and 21-fold, respectively. None of the strains showed RR(KC50) >10 with deltamethrin, and moderate resistance was seen in three strains, while the rest were susceptible. Mosquitoes from all strains exhibited some recovery from all pyrethroids except d-phenothrin. Regression analysis was used to analyze the relationship between RR(LC50) and RR(KC50). Both were highly correlated (R2 = 0.84-0.97) so that the slope could be used to determine how much additional pyrethroid was needed to ensure lethality. Slopes ranged from 0.875 for d-phenothrin (RR(LC50) approximately equal to RR(KC50)) to 8.67 for lambda-cyalothrin (-8.5-fold more insecticide needed to kill). Both RR(LC50) and RR(KC50) values were highly correlated for all pyrethroids except bifenthrin indicating strong cross-resistance. Bifenthrin appears to be an alternative pyrethroid without strong cross-resistance that could be used as an alternative to the current widespread use of permethrin in Mexico.
authors.affiliation: Universidad Autonoma de Nuevo Leon, Facultad de Ciencias Biologicas, Laboratorio de Entomologia Medica, Av. Universidad s/n. San Nicolas de los Garza, Nuevo Leon 66451, Mexico. adriana.floressr@uanl.edu.mx
authors.forename: Adriana E
authors.initials: AE
authors.lastname: Flores
authors.forename: Gustavo
authors.initials: G
authors.lastname: Ponce
authors.forename: Brenda G
authors.initials: BG
authors.lastname: Silva
authors.forename: Selene M
authors.initials: SM
authors.lastname: Gutierrez
authors.forename: Cristina
authors.initials: C
authors.lastname: Bobadilla
authors.forename: Beatriz
authors.initials: B
authors.lastname: Lopez
authors.forename: Roberto
authors.initials: R
authors.lastname: Mercado
authors.forename: William C
authors.initials: WC
authors.lastname: Black
mesh_terms: D000330:Aedes / Q000235:genetics; D000818:Animals; D005260:Female; D007305:Insecticide Resistance; D007306:Insecticides; D008800:Mexico; D011722:Pyrethrins; D013997:Time Factors
chemical_list: D007306:Insecticides; D011722:Pyrethrins