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Updated: Apr 3, 2026
A Multi-detection Assay for Malaria Transmitting Mosquitoes
Published on: February 28, 2015
Molecular detection of the kdr T917I mutation in head lice (psocodea: pediculidae) from Malaysia and its increasing
Aida Syafinaz Mokhtar1, Adriana Zahanuddin1, Yee Ling Lau1
1Department of Parasitology, Faculty of Medicine, Universiti Malaya, Kuala Lumpur, Malaysia.
Abstract:
Pediculosis capitis remains a common ectoparasitic infestation in Malaysia, particularly among children in overcrowded and resource-limited settings. Permethrin-based pediculicides continue to be widely used; however, global reports of knockdown resistance (kdr) mutations in the voltage-sensitive sodium channel gene raise concerns regarding reduced treatment efficacy. Despite extensive epidemiological data on infestation by head lice (Pediculus humanus capitis De Geer) in Malaysia, the molecular kdr status of local populations has not previously been examined. This study provides a temporal molecular evaluation of the kdr T917I mutation by comparing head lice collected from underprivileged children in the Klang Valley in 2015 and 2025. Genotyping was performed using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) targeting the T917I locus, with bidirectional sequencing for confirmation. In 2015, head lice were predominantly homozygous susceptible (SS, 96.8%), with a low proportion of heterozygous (RS, 3.2%) and no homozygous resistant (RR) genotypes detected. In contrast, the 2025 collection showed a marked shift in genotypic distribution, with SS decreasing to 60.6% and RS increasing to 39.4%, while RR genotypes remained absent. Correspondingly, the resistance-associated allele frequency increased from 1.6% in 2015 to 19.7% in 2025. Several establishments sampled in 2025 exhibited heterozygote excess and deviations from Hardy-Weinberg equilibrium; however, given differences in sampling structure between collection periods, these patterns should be interpreted cautiously and may reflect heterozygous treatment exposure or population substructure rather than directional selection alone. This study provides the first molecular detection and temporal comparison of the T917I mutation in Malaysian head lice populations and establishes baseline data for future resistance monitoring.
Insights
Head lice resistance to permethrin is increasing in Malaysia. Molecular analysis shows a significant rise in the T917I mutation frequency in head lice populations between 2015 and 2025, indicating reduced treatment efficacy.
Area of Science:
- Medical Entomology
- Molecular Biology
- Parasitology
Background:
- Pediculosis capitis (head lice infestation) is prevalent in Malaysian children, often treated with permethrin-based pediculicides.
- Global reports of knockdown resistance (kdr) mutations in head lice raise concerns about the effectiveness of current treatments.
- The molecular status of kdr mutations in Malaysian head lice populations remains unexamined.
Purpose of the Study:
- To conduct a temporal molecular evaluation of the kdr T917I mutation in head lice from Malaysia.
- To compare the prevalence of the T917I mutation in head lice collected in 2015 and 2025.
- To establish baseline data for future monitoring of head lice resistance.
Main Methods:
- Head lice samples were collected from underprivileged children in the Klang Valley in 2015 and 2025.
- Genotyping of the T917I mutation was performed using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP).
- Bidirectional sequencing was used for confirmation of the mutation.
Main Results:
- In 2015, head lice were predominantly homozygous susceptible (96.8% SS), with a low frequency of heterozygotes (3.2% RS) and no resistant genotypes (RR).
- By 2025, the genotypic distribution shifted significantly, with a decrease in SS (60.6%) and an increase in RS (39.4%), while RR remained absent.
- The resistance-associated allele frequency rose from 1.6% in 2015 to 19.7% in 2025.
Conclusions:
- This study presents the first molecular detection and temporal comparison of the T917I mutation in Malaysian head lice.
- A significant increase in the kdr T917I allele frequency indicates a growing resistance to permethrin in local head lice populations.
- The findings highlight the need for ongoing monitoring and potential adaptation of treatment strategies for pediculosis capitis in Malaysia.
