Frequency of knockdown resistance alleles to pyrethroid insecticides in head louse (Pediculus humanus capitis) populations from Chile (Human lice)

ROCA ACEVEDO, GONZALO; TOLOZA A

Conferencia; International Conference on Phthiraptera 6; 2018

The human head louse, Pediculus humanus capitis has been in contact with humans since thebeginning of humankind and is an obligate ectoparasite that causes Pediculosis. Head louse infestations arewidespread throughout the world, and have been increasing since the beginningof the 1990s partially due to ineffectiveness pediculicides. The overuse ofproducts containing permethrin has led to the development of resistant lousepopulations. Pyrethroid insecticides act on the nervous system affectingvoltage-sensitive sodium channels. Three point mutations (M815I, T917I andL920F) in the voltage-gated sodium channel gene are responsible forcontributing to knockdown resistance (kdr). The management of pyrethroidresistance requires either early detection or the characterization of themechanisms involved in resistant head louse populations. In this work, thegeographic distribution of kdralleles of head lice from four geographic regions of Chile was estimated. Resistancealleles were found in frequencies ranging from 4% to 95%. The populationsdiffered considerably in their allelic composition: Vallenar, 54% homozygousresistant, 45% heterozygous; Talca, 95% heterozygous, 4% homozygous susceptible;Las Condes, 81% heterozygous, 18% homozygous susceptible; and Lo Barnechea, 91%heterozygous, 8% homozygous susceptible. Based on this, we can conclude that thestudied Chilean populations of head lice are still under selective pressure.