MOLECULAR INVESTIGATION OF KNOCKDOWN RESISTANCE MUTATION IN HEAD LICE (PEDICALUS HUMANS CAPITIS) FROM ELEMENTARY SCHOOL CHILDREN IN LOPBURI AND SING BURI PROVINCES, THAILAND

Abstract

The objective of this study was to investigate the kdr mutations in head louse (Pediculus humanus capitis). A total of 74 head lice samples were collected from primary school students in Lop Buri and Sing Buri provinces, Thailand, from grades 1 to 6. A total of 40 head samples (54.5%) were collected from Lop Buri, while 34 samples (45.95%) were obtained from Sing Buri. The present study has analyzed the mutation patterns of drug resistance genes in pyrethroids at the T917I codon using the PCR-RFLP technique. The results showed that head louse with a mutation at codon T917I in the voltage sensitive sodium channel (VSSC) gene had a mutation rate, which was 81.08%. Genotypic analysis showed that the most common pattern was homozygous resistant (R/R) (81.08%), followed by heterozygous resistant (R/S) at 10.81% and homozygous susceptible (S/S) at 8.11%. The mutation frequency was 0.86. In addition, the Hardy-Weinberg analysis showed that the head lice population in Lopburi province was out of equilibrium, while the population in Sing Buri province was in equilibrium. The results of this study indicate the need to improve head louse control methods in Thailand by reducing the use of pyrethroids and developing integrated control methods, such as the use of other insecticides from natural sources, as well as continuous monitoring for resistance gene mutations.