First evidence of the mutations associated with pyrethroid resistance in head lice (Phthiraptera: Pediculidae) from Honduras

LARKIN, KELSEY; RODRÍGUEZ, CAROL; JAMANI, SHABANA; FRONZA, GEORGINA; ROCA ACEVEDO, GONZALO; SÁNCHEZ, ANA; TOLOZA, ARIEL

PARASITES AND VECTORS

BIOMED CENTRAL LTD

Lugar: Londres; Año: 2020

1756-3305

Background: The human head louse, Pediculus humanus capitis, is a cosmopolitan bloodsucking ectoparasite affecting mostly schoolchildren in both developed and developing countries. In Honduras, chemical pediculicides are the first line of treatment, with permethrin as their main active ingredient. Despite the extended use of these products, there is currently no research investigating insecticide resistance in Honduran head lice. In head lice, the most common mechanism is knockdown resistance (kdr), which is the result of two-point mutations and the associated amino acid substitutions, T917I and L920F, within the voltage-sensitive sodium channel (VSSC). Methods: Genomic DNA was extracted from 83 head lice collected in the Honduran localities of San Buenaventura and La Hicaca. Polymerase chain reaction (PCR) was used to amplify a 332-bp fragment of a VSSC gene that contains a site affected by C/T mutation which results in a T917I amino acid substitution on each human head louse genomic DNA fragments.Results: The C/T nonsynonymous mutation which results in the T917I kdr amino acid substitution was detected in both head lice populations at frequencies ranging between 0.45-0.5. Globally, the frequency of this substitution was 0.47. Of these, 5 (6.1%) were homozygous susceptible and 78 (93.9%) were heterozygotes. The kdr-resistant homozygote (RR) was not detected in the studied populations. Thus, 93.9% of the collected Honduran head lice harbored only one T917I allele. Exact test for the Hardy-Weinberg equilibrium for both localities showed that genotype frequencies differed significantly from expectation. In addition, San Buenaventura and La Hicaca populations had an inbreeding coefficient (Fis)