Serial invasive signal amplification reaction for genotyping permethrin-resistant (kdr-like) human head lice, Pediculus capitis

Permethrin resistance in the human head louse, Pediculus capitis De Geer (Anopulura: Pediculidae), has been reported worldwide, is associated with the knockdown phenotype, and elicits cross-resistance to DDT and the pyrethrins. Two point mutations, T929I and L932F, in the voltage-sensitive sodium channel α-subunit gene are responsible for permethrin resistance as a resistant haplotype (kdr-like). We have optimized a serial invasive signal amplification reaction (SISAR) protocol for the detection of these mutations using PCR amplified DNA fragments. SISAR distinguished all genotypes with high accuracy in a head louse population from Texas that was heterogeneous in terms of permethrin sensitivity. Using SISAR, resistance-conferring mutations are detected in a high throughput format, facilitating the efficient monitoring of permethrin resistance allele frequency in field populations.     

Determination of knockdown resistance allele frequencies in global human head louse populations using the serial invasive signal amplification reaction

BACKGROUND: Pediculosis is the most prevalent parasitic infestation of humans. Resistance to pyrethrin‐ and pyrethroid‐based pediculicides is due to knockdown (kdr)‐type point mutations in the voltage‐sensitive sodium channel α‐subunit gene. Early detection of resistance is crucial for the selection of effective management strategies. RESULTS: Kdr allele frequencies of lice from 14 countries were determined using the serial invasive signal amplification reaction. Lice collected from Uruguay, the United Kingdom and Australia had kdr allele frequencies of 100%, while lice from Ecuador, Papua New Guinea, South Korea and Thailand had kdr allele frequencies of 0%. The remaining seven countries investigated, including seven US populations, two Argentinian populations and populations from Brazil, Denmark, Czech Republic, Egypt and Israel, displayed variable kdr allele frequencies, ranging from 11 to 97%. CONCLUSION: The newly developed and validated SISAR method is suitable for accurate monitoring of kdr allele frequencies in head lice. Proactive management is needed where kdr‐type resistance is not yet saturated. Based on sodium channel insensitivity and its occurrence in louse populations resistant to pyrethrin‐ and pyrethroid‐based pediculicides, the T917I mutation appears to be a key marker for resistance. Results from the Egyptian population, however, indicate that phenotypic resistance of lice with single or double mutations (M815I and/or L920F) should also be determined. Copyright © 2010 Society of Chemical Industry