Activity of increased specific and non-specific esterases and glutathione transferases associated with permethrin-resistance in Pediculus humanus capitis (Phthiraptera: Pediculidae) from Argentine

46. BARRIOS S., E. ZERBA, M. I. PICOLLO & P. GONZÁLEZ AUDINO

PARASITOLOGY RESEARCH

SPRINGER

Año: 2010 vol. 106 p. 415 - 421

0932-0113

Enhanced metabolism by oxidative enzymes is amajor cause of pyrethroid resistance in insects. In this work,we evaluated the role of specific and non-specific esterasesin head louse populations from Buenos Aires with differentlevels of resistance to permethrin. As esterase activity issubstrate-dependent, four different esters were used asunspecific substrates in order to obtain a better characterizationof the possible role of these enzymes in the resistancephenomenon. The unspecific substrates were phenylthioacetate,1- and 2-naphtyl-acetate, and p-nitrophenyl acetate. A 7-coumaryl permethrate was synthesized and used as a specificsubstrate to measure pyrethroid esterases by a very sensitivemicrofluorometric method. The results on pyrethroid esteraseactivity obtained with this substrate showed that theseenzymes contribute to the detoxifying activity in resistantpopulations, although no correlation was found betweenpyrethroid esterase activity and resistance ratios. In thisstudy, we established that the activity of esterase againstspecific and non-specific substrates is increased in pyrethroidresistantpopulations of head lice from Buenos Aires. Also,dichlorodiphenyltrichloroethane (DDT) resistance valuesdemonstrated that there is a DDT cross-resistance phenomenonin pyrethroid-resistant head louse populations andsuggested that an alteration in the receptor of the nervoussystem (kdr gen) is a key factor of the resistance phenomenain these head louse populations.