First Report of the Gene Mutations Associated with Permethrin Resistance in Head Lice (Pediculus humanus capitis De Geer, 1767) from Primary School Children in Istanbul (Türkiye) and Nagarkot (Nepal).

Head lice infestation (HLI), caused by Pediculus humanus capitis De Geer, 1767, has long been a common global problem of school children. Permethrin is an old pyrethroid derivative that has been used commonly for its treatment, and it exerts its activity over the voltage-sensitive calcium channels (VSCC) of the lice. There has been a growing list of persistent HLI cases lately in the world among patients using permethrin, and knockdown resistance (kdr)-related point mutations on VSCC have been identified and reported from those resistant lice samples. The aim of this study was to investigate the gene mutations associated with permethrin resistance in head lice collected from primary school children in Istanbul (Türkiye) and Nagarkot (Nepal) for the first time. A total of 192 P. h. capitis adults were collected from school children aged 6-12 years in two cities (96 lice each). Following DNA isolation, the fragment of the VSCC a-subunit gene, which contained the possible mutation sites ((kdr-like M815I (ATG > ATT), kdr T917I (ACA > ATA), and kdr-like L920F (CTT > TTT)), was amplified in each louse by PCR, and the PCR products were sequenced and aligned, followed by frequency calculations for alleles, genotypes, and haplotypes. Using nucleic acid sequence analysis, it was revealed that M815I, T917I, or L920F mutations were present on the VSCC genes in the lice samples from both Türkiye and Nepal. In addition, genotypic analyses indicated the presence of all three mutations in the lice samples from Türkiye, while the T917I mutation was detected in none of the lice collected in Nepal. This is the first report of gene mutations associated with permethrin resistance in head lice collected from a group of primary school children in the largest city of Türkiye (Istanbul) and Nagarkot. High mutation rates were identified in the lice, especially those from Istanbul, which is concordant with our previous unpublished study, in which almost 60% of the examined lice of the school children (in the same school selected in this study) remained alive despite long-term exposure to permethrin in the laboratory. These initial results show that gene mutations associated with permethrin resistance are common in lice samples in Istanbul and Nagarkot, which may suggest the current need for the selection of new pediculicidal agents in HLI treatment.