Pyrethroid pediculicide resistance of head lice in Canada evaluated by serial invasive signal amplification reaction.
BACKGROUND
Most people in the United States and Canada with pediculosis will be treated with neurotoxic pediculicides containing pyrethrins or pyrethroids. Their widespread use led to significant resistance reported from various countries. Although treatment failures are frequently observed in Canada, the resistance frequency to pyrethroid pediculicide of human head lice (Pediculus humanus capitis) has not been determined.


OBJECTIVE
To determine the knockdown resistance (kdr) allele frequency in human head louse populations in Canada.


METHODS
Patients infested with Pediculus humanus capitis, aged 4 to 65 years, residents of Ontario, Quebec, and British Columbia, were participants. Head lice were collected by combing and picking the enrolled subjects' hair. Lice were analyzed by serial invasive signal amplification reaction (SISAR) for genotyping the T917I mutation of lice indicating permethrin resistance. The permethrin-resistant kdr allele (R allele) frequency could then be evaluated in the head lice collected in Canada.


RESULTS
Of the head louse populations analyzed, 133 of 137 (97.1%) had a resistant (R) allele frequency, whereas only 4 of 137 (2.9%) had a susceptible (S) allele frequency.


CONCLUSIONS
The 97.1% resistant (R) allele frequency in head lice from Canada could explain the treatment failures encountered with pyrethrin and pyrethroid pediculicide treatments in Canadian populations infested with Pediculus humanus capitis as the latter will not be eliminated by those pediculicides.
Marcoux
Danielle
D
Department of Pediatrics, Dermatology Division, CHU Sainte-Justine, University of Montreal, Montreal, QC.
Palma
Kathleen G
KG
Kaul
Nalini
N
Hodgdon
Hilliary
H
Van Geest
Andrea
A
Previte
Dominic J
DJ
Abou-Elghar
Gamal Elsayed
GE
Yoon
Kyong Sup
KS
Clark
J Marshall
JM
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D002170:Canada; D002648:Child; D002675:Child, Preschool; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology*; D010373:Lice Infestations / Q000188:drug therapy; D008297:Male; D008875:Middle Aged; D009154:Mutation; D062550:NAV1.1 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins / Q000235:genetics*; D010374:Pediculus / Q000187:drug effects / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D011722:Pyrethrins / Q000494:pharmacology*; D012536:Scalp Dermatoses / Q000188:drug therapy; D015222:Sodium Channels / Q000235:genetics*; D055815:Young Adult
D007306:Insecticides; D062550:NAV1.1 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins; D011722:Pyrethrins; C568242:SCN1A protein, human; D015222:Sodium Channels