Molecular evidence of knockdown resistance (kdr) mutations in the head lice (Pediculus humanus capitis) collected from disadvantaged children in Klang Valley, Malaysia

Pediculosis capitis, caused by infestation of the human head louse Pediculus humanus capitis is endemic all over the world, and Malaysia is no exception. Permethrin is recommended as one of the first-line treatments for pediculosis capitis. However, after decades of intensive and continuous use, numerous treatment failures and recurrent cases have been reported globally due to established evidence of permethrin resistance. The fact that permethrin-based products are still widely used and available over the counter prompted this study to investigate the genotypic basis of permethrin resistance and to identify kdr alleles in head lice collected from seven children shelters located across Klang Valley, Malaysia. The PCR-RFLP employed in this study successfully demonstrated the kdr T917I mutation in head lice resulting in two genotypes: 31 (49.21%) homozygous susceptible (SS) and 32 (50.79%) heterozygous resistant (RS). These findings provide baseline data on permethrin resistance in Malaysia, which has not been previously investigated.