Detection of pyrethroid resistance gene in head lice in schoolchildren from Bobigny, France.

The head louse, Pediculus humanus capitis (De Geer), is an hematophagous ectoparasite that affects mainly children. Resistance to insecticides belonging to pyrethroids and other pediculicides, such as malathion, is responsible for frequently reported treatment failures. Recent studies showed that a M815I-T929I-L932F kdr-like mutation in the voltage-gated sodium channel alpha-subunit gene was associated with permethrin resistance in head lice from several countries worldwide. We searched for the presence ofpyrethroid resistance gene in head lice populations obtained in schoolchildren in an urban area of France. All the 15 primary schools of Bobigny, a city located 3 km north of Paris, were selected to participate. Of 3,493 children enrolled, 3,345 (95.8%) children were screened for head lice by using fine-toothed antilouse combs. Live head lice were detected in 112 (3.3%) of children screened. A subsample of 90 lice was processed for DNA study. The amplification of a 332-bp portion of the kdr-like gene spanning the codon 929 was performed, and polymerase chain reaction products were submitted to the restriction enzyme SspI. Twenty of these lice (22.2%) were homozygous susceptible, 33 (36.7%) were homozygous resistant, and 37 (41.1%) were heterozygotes. Globally, the frequency of the T929I mutation was 0.57. The prevalence of pediculosis in schoolchildren of Bobigny seemed relatively low in comparison with findings of other European studies. The presence of the T929I mutation associated with permethrin resistance probably reflected the frequent local use of this insecticide. Further studies are now required to evaluate the prevalence of the kdr-like mutant allele in head lice in French schools.