Head lice

Pediculosis, caused by head lice (Pediculidae: Pediculus humanus var. capitis), is experiencing a global resurgence, with the prevalence in primary schools averaging as high as 40% in some areas regardless of socioeconomic factors. Control efforts using chemical treatments are becoming increasingly ineffective, with insecticide resistance recorded in several countries. Prevention using repellents and oils would be useful if they limited transmission. Many commercially available substances reputedly have effective repellent qualities, but remain untested. This study tested the preventative efficacy of N,N-diethyl-3-methylbenzamide (DEET) against several commercially available botanicals to clarify their value as transmission inhibitors, irritants, repellents, and antifeedants. The transfer of head lice to treated hairs was limited by the slippery nature of the oils rather than their repellent qualities. Irritancy was not important because lice proceeded despite being highly irritated...

Despite the meticulous care bestowed by Ancient Egyptian embalmers, numerous mummies have suffered from attacks by depredatory insects. The Egyptian mummy from the Museum Anne de Beaujeu, entrusted for restoration to the C2RMF (Versailles), did not escape the invasions of thanatophagous arthropoda, which have been preserved up till now. Beyond this post-mortem colonization, paleoparasitological investigations conducted on this mummy revealed that the latter suffered from severe pediculosis, as evidenced by the myriads of lice and nits discovered on the remaining hair.

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. 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%.
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.

Genetic analyses of human lice have shown that the current taxonomic classification of head lice (Pediculus humanus capitis) and body lice (Pediculus humanus humanus) does not reflect their phylogenetic organization. Three phylotypes of head lice A, B and C exist but body lice have been observed only in phylotype A. Head and body lice have different behaviours and only the latter have been involved in outbreaks of infectious diseases including epidemic typhus, trench fever and louse borne recurrent fever. Recent studies suggest that body lice arose several times from head louse populations. By introducing a new genotyping technique, sequencing variable intergenic spacers which were selected from louse genomic sequence, we were able to evaluate the genotypic distribution of 207 human lice. Sequence variation of two intergenic spacers, S2 and S5, discriminated the 207 lice into 148 genotypes and sequence variation of another two intergenic spacers, PM1 and PM2, discriminated 174 lice ...

Human head and body lice are obligatory
hematophagous ectoparasites that belong to a single
species, Pediculus humanus. Only body lice, however,
are vectors of the infectious Gram-negative
bacterium Bartonella quintana. Because of their near
identical genomes, yet differential vector competence,
head and body lice provide a unique model
system to study the gain or loss of vector competence.
Using our in vitro louse-rearing system, we
infected head and body lice with blood containing B.
quintana in order to detect both differences in the
proliferation of B. quintana and transcriptional differences
of immune-related genes in the lice. B. quintana
proliferated rapidly in body lice at 6 days postinfection,
but plateaued in head lice at 4 days postinfection.
RNAseq and quantitative real-time PCR
validation analyses determined gene expression
differences. Eight immunoresponse genes were
observed to be significantly different with many associated with the Toll pathway: Fibrinogen-like
protein, Spaetzle, Defensin 1, Serpin, Scavenger
receptor A and Apolipoporhrin 2. Our findings
support the hypothesis that body lice, unlike head
lice, fight infection from B.

Genetic analyses of human lice have shown that the current taxonomic classification of head lice (Pediculus humanus capitis) and body lice (Pediculus humanus humanus) does not reflect their phylogenetic organization. Three phylotypes of head lice A, B and C exist but body lice have been observed only in phylotype A. Head and body lice have different behaviours and only the latter have been involved in outbreaks of infectious diseases including epidemic typhus, trench fever and louse borne recurrent fever. Recent studies suggest that body lice arose several times from head louse populations. By introducing a new genotyping technique, sequencing variable intergenic spacers which were selected from louse genomic sequence, we were able to evaluate the genotypic distribution of 207 human lice. Sequence variation of two intergenic spacers, S2 and S5, discriminated the 207 lice into 148 genotypes and sequence variation of another two intergenic spacers, PM1 and PM2, discriminated 174 lice ...