Le pou de tête et le pou de corps sont deux écotypes indiscernables occupant chacun une niche écologique différente. Le pou de corps représente une menace réelle pour l'Homme en raison de son rôle de vecteur dans la transmission de trois maladies graves pour l'Homme à savoir: le typhus épidémique, la fièvre des tranchées et la fièvre récurrente. Dans cette thèse, nous avons obtenu des résultats concrets dans chacune des thématiques abordées. En effet, nous avons (i) mis en place un outil moléculaire qui permet de différencier pour la première fois entre le pou de tête et le pou de corps qui a montré efficacité sur le terrain, (ii) mis en évidence l'existence d'un nouveau clade mitochondrial (Clade D) renfermant des poux de tête et des poux de corps susceptible de vectoriser Bartonella quintana et Yersinia pestis, (iii) retracé les migrations humaines à travers l'analyse de poux anciens provenant de différentes périodes et localisations, (iv) démontré pour la première fois que Pediculus mjobergi est génétiquement proche du pou humain et confirmé l'hypothèse qu'à l'origine Pediculus mjobergi était un pou humain qui a été transféré aux singes du Nouveau Monde par les premiers Hommes à avoir atteint le continent américain il y a des milliers d'années et (v) mis en place un outil de détection et de contrôle de la résistance moléculaire des poux à la perméthrine. Cet outil fut particulièrement utile dans l'étude clinique que nous avons menée pour déterminer si l'utilisation de sous-vêtements imprégnés d'insecticide offrait une protection efficace à long terme contre les poux de corps infestant les personnes sans-abri.

Head louse (Pediculus humanus capitis) and body louse (Pediculus humanus humanus) are two indistinguishable ecotypes each occupying an ecological niche: hair for head louse and clothing for the body louse. Body louse represents a real threat to humans because of its role as vector for the transmission of three deleterious diseases namely epidemic typhus, trench fever and relapsing fever.In this thesis, we obtained concrete results that have led to scientific publications. Indeed, we (i) implemented a molecular tool to differentiate for the first time between head and body louse, (ii) we highlighted the existence of a fourth mitochondrial clade (Clade D) comprising head and body lice that can vectorize Bartonella quintana and Yersinia pestis, (iii) we traced human migration through the analysis of ancient lice from different periods and different area, (iv) we demonstrated for the first time that Pediculus mjobergi is genetically close to human louse and confirmed the hypothesis that initially Pediculus mjobergi was a human louse has been transferred to New World monkeys by the first humans who have reached the American continent thousands of years ago and (v) we have implemented a tool for detecting and monitoring the molecular resistance to permethrin of body lice that parasite sheltered homeless persons in Marseille. This tool was particularly useful in the clinical study we conducted to determine…

Advisors/Committee Members: Brouqui, Philippe (thesis director), Raoult, Didier (thesis director).

With the advent of sequencing technologies that are both affordable and readily available, biologists are now able to address questions that were previously intractable. New species are having their genomes mapped at an increasing rate, including non-model organisms. Two such organisms are the human body louse, Pediculus humanus corporis and the black cottonwood, Populus trichocarpa. While unrelated, these two organisms each represent a study system with questions that challenge our current understanding of each organism. Body and head lice, while closely related, are thought to be separate species with their most important difference being that only body lice vector disease to humans. The first question is: Are body lice (Pediculus humanus coporis) and head lice (Pediculus humanus capitis) the same species? A total of 10,771 body louse and 10,770 head louse transcripts were predicted from a combined assembly of Roche 454 and Illumina sequenced cDNAs from whole body tissues collected at all life stages and during pesticide exposure and bacterial infection treatments. Illumina reads mapped to the 10,775 draft body louse gene models from the whole genome assembly predicted nine presence/absence differences, but PCR confirmation resulted in a single gene difference. One novel microRNA was predicted in both lice species and 99% of the 544 transcripts from Candidatus riesia indicate that they share the same endosymbiont. Overall, few differences exist, which supports the hypothesis that these two organisms are ecotypes of the same species. A second question is: Are there gene expression differences between these two organisms that cause the body louse to vector disease to humans while head lice do not? We utilized an RNAseq analysis on 7-day old head and body lice fed blood infected with Bartonella quintana, the bacterium that causes trench fever, and control individuals to elicit gene expression differences. Eight immunoresponse genes came out significant, many associated with the Toll pathway; Fibrinogen-related protein (PHUM500950), Spaetzle (PHUM595260), Defensin 1 (PHUM365700) and 2 (PHUM595870), Serpin (PHUM311330), Cactus (PHUM345810), Scavenger receptor A (ScavA; PHUM066640) and Apolipoprotein D (PHUM427700). Increased expression of Fibrinogen-related protein and Spaetzle, both related to the Toll pathway, in treated body lice supports the hypothesis that body lice are fighting infection from B. quintana. But conflicting results in Defensin 1 and 2 based upon validation method suggest another mechanism in head lice alternative to the Toll pathway might be involved. Additionally, Scavenger receptor A was higher in both control and treated head lice, suggesting higher phagocytotic activity in head lice to curb infection. In 1981, Whitham and Slobodchikoff hypothesized that long-lived plant species, like black cottonwood, that propagate both asexually and sexually, might develop, through accumulation of somatic mutations, as genetic mosaics, providing the potential to respond to or even outrun their insect… Advisors/Committee Members: Paige, Ken N. (advisor), Pittendrigh, Barry R. (advisor), Paige, Ken N. (Committee Chair), Pittendrigh, Barry R. (Committee Chair), Hudson, Matthew E. (committee member), Malhi, Ripan S. (committee member).