ABSTRACT
BACKGROUND: Treatment of head lice infestation relies on the application of topical insecticides. Overuse of these products has led to the emergence of resistance to pyrethroids and malathion worldwide. Permethrin resistance in head lice is mostly conferred by the knockdown resistance (kdr) trait. OBJECTIVE: To evaluate the occurrence of permethrin- and malathion-resistant head lice in Paris. METHODS: A prospective survey was conducted in 74 elementary schools. Live lice collected on schoolchildren were randomly selected and submitted to ex vivo bioassays or underwent individual DNA extraction. A fragment of kdr-like gene was amplified and compared with wild-type sequences. RESULTS: Live head lice were detected in 574 children. Ex vivo assays showed no surviving lice after a 1-hour contact with malathion while most lice died after a 1-hour exposure to permethrin and piperonyl butoxide (85.7%, 95% confidence interval [CI]: 83.9-87.5). Among the 670 lice with workable DNA sequences, 661 lice (98.7%, 95% CI 97.7-99.3) had homozygous kdr mutations. LIMITATIONS: The findings of this large-scale survey of the occurrence of insecticide-resistant head lice indicated a major insecticide pressure in the study population, but it was not sufficient to draw conclusions about other populations. The presence of T917I-L920F mutations in kdr gene may not correlate with treatment failure in prospective studies. CONCLUSION: The high occurrence of kdr mutant allele suggests that insecticide resistance was already strongly established in the studied population. This finding must be interpreted with caution as it may not be predictive of treatment failure.
Subject(s)
Insecticides/therapeutic use , Lice Infestations/drug therapy , Malathion/therapeutic use , Pediculus/drug effects , Permethrin/therapeutic use , Animals , Child , Female , Humans , Insecticide Resistance , Male , Pediculus/genetics , Prospective StudiesABSTRACT
The human body louse is the only known vector of Bartonella quintana. However, the presence of this bacterium has recently been detected in the head lice of homeless individuals and Nepalese slum children. Previous studies have reported the isolation of Acinetobacter baumannii from the body lice of homeless individuals. An epidemiological survey including 74 schools was conducted between 2008 and 2009 in Paris. After a first visual examination, the hair of children with suspected pediculosis was combed with a fine-tooth comb to collect live adult head lice. Molecular studies were performed on randomly selected DNA samples to detect B. quintana and A. baumannii by specific quantitative real-time PCR. Among a collection of 288 DNA samples, B. quintana was not detected, but A. baumannii was detected in 95 DNA samples (33%). Further study is needed to determine the significance of the finding of A. baumannii in head lice.
Subject(s)
Acinetobacter baumannii/isolation & purification , Bartonella quintana/isolation & purification , Lice Infestations/microbiology , Pediculus/microbiology , Scalp Dermatoses/microbiology , Acinetobacter baumannii/genetics , Animals , Bartonella quintana/genetics , Child , Humans , Lice Infestations/epidemiology , Paris/epidemiology , Scalp Dermatoses/epidemiologyABSTRACT
Resistance of head lice to pyrethroids induces difficult therapeutic problems. Previous studies demonstrated that this resistance was present in a French urban area, but its prevalence needed to be more precisely evaluated in terms of genotyping lice collected from more infested children over a certain period of time. We monitored the presence of the head lice kdr-like haplotype of the voltage-gated sodium channel alpha-subunit gene in schoolchildren seen three times on a 6-wk period. The prevalence of pediculosis was 2.39% (n = 1551). Genotyped lice (n = 167) were homozygous resistant in all but one pupil. The high frequency of the mutant haplotype (0.93) advocated for the abandonment of pyrethroid insecticides in this area and for the consideration of other treatment options.
