Dans ce travail, nous avons voulu apporter notre contribution dans le domaine de la recherche sur les poux humains, afin d’en savoir plus sur l’origine et la phylogéographie des clades, les pathogènes qui leurs sont associés et comprendre les mécanismes impliqués dans la résistance à l’ivermectine. Nous avons obtenu des résultats concrets dans chacune des thématiques abordées. En effet, nous avons (i) pour la première fois rapporté la présence de clade B au Moyen-Orient datant de plus de 2000 ans, supportant une origine asiatique pour ce clade, (ii) mis en évidence l'existence d'un nouveau clade mitochondrial (Clade F), (iii) mis en place une nouvelle technique de PCR en temps réel pour l’identification moléculaire rapide des clades de poux, (iv) mis en évidence chez des poux de tête la présence de l’ADN de plusieurs bactéries, dont plusieurs bactéries qui ne sont pas habituellement vectorisées par les poux telles que Coxiella burnetii, Rickettsia aeschlimannii et de potentielles nouvelles espèces de genre Anaplasma et Ehrlichia ont été détectées pour la première fois chez les poux. Enfin, nous rapportons des données nouvelles sur la résistance des poux à l’ivermectine : (v) en mettant en évidence la présence de trois mutations non-synonymes au niveau de GluCl des poux cliniquement résistants à l’ivermectine, (vi) et en démontrant, pour la première fois, chez une population de poux de laboratoire résistante à l’ivermectine qu’une répression significative de la complexine est à l’origine de la résistance. Cette découverte représente la première évidence liant la complexine à la résistance aux insecticides. / In this thesis, we are interested in studying human lice and we aimed to learn more about the origin and phylogeography of clades, lice-borne associated pathogens and to investigate potential mechanisms underlying resistance to ivermectin in lice. We obtained concrete results that have led to scientific publications. Indeed, (i) we reported for the first time the existence of the clade B in the Middle East, dating approximately to 2,000 years old, supporting an Asian origin for this clade, (ii) we highlighted the existence of a sixth mitochondrial clade (Clade F), (iii) we developed a new qPCR for a quick molecular identification of all the known clades of lice, (iv) we identified the presence of the DNA of several bacterial pathogens in head lice, among which several bacteria are not usually associated with lice, such as Coxiella burnetii, Rickettsia aeschlimannii, Borrelia theileri and potential new species from the Anaplasma and Ehrlichia. We finally, investigated mechanisms underlying resistance to ivermectin in lice: (v) we have identified, for the first time, the occurrence of three non-synonymous mutations in GluCl gene in clinically confirmed ivermectin resistant head lice, (vi) and we have identified the involvement of neuronal protein, a complexin, in laboratory ivermectin-selected resistant lice. This finding represents the first evidence linking complexin to insecticide resistance.

Les poux humains (Pediculus humanus) sont des ectoparasites hématophages, ayant vécu avec leur hôte pendant des milliers d’années. Durant cette thèse, nous avons d’abord élaboré une large bibliographie nous permettant de rédiger une revue, puis d’apporter des réponses à certains nombres de questions restées en suspens à travers le traitement de certaines thématiques qui nous semblaient importantes. En effet, nous avons (i) démontré que les poux de tête et les poux de corps en Afrique peuvent être infectés par B. quintana quand les patients vivent dans des conditions économiques pauvres et sont aussi exposés aux poux de corps; identifié pour la première fois le clade mitochondrial des poux de tête du Mali, Kenya, Congo et Madagascar, et confirmé celui du Sénégal, Algérie, Ethiopie, Rwanda et Burundi, (ii) démontré que les poux de tête et les poux de corps chez les SDF doublement infestés appartiennent à la même population de poux de corps, et dans les conditions d’infestation massive, les poux de corps peuvent migrer et coloniser les cheveux et vice-versa, (iii) prouvé la nécessité de réaliser des enquêtes épidémiologiques nationales sur la pédiculose dans les régions du Mali, (iv) démontré par le modèle in vitro que la doxycycline a un effet direct sur la bactérie endosymbionte du pou Candidatus Riesia pediculicola via le mycetome. Ce dernier travail nous a permis de mettre en exergue l’efficacité synergique des antibiotiques + ivermectine permettant de lutter plus efficacement l’infestation des poux et éviter l’apparition de résistance. Ce travail a fait l’objet de dépôt d’un brevet. / Human lice (Pediculus humanus) are bloodsucking ectoparasites, having lived with their host for thousands of years. During this thesis, we first developed an extensive bibliography allowing us to write a review and provide answers to certain number of questions remained pending through treating some thematic that seemed us significant. Indeed, we have (i) demonstrated that head and body lice in Africa can be infected with B. quintana when patients live in poor economic conditions and are also exposed to body lice; identified for the first time the mitochondrial clade of lice Mali, Kenya, Congo and Madagascar, and confirmed that of Senegal, Algeria, Ethiopia, Rwanda and Burundi, (ii) demonstrated that head and body lice in SDF doubly infected belong to the same population of body lice, and under conditions of massive infestation, body lice can migrate and colonize the hair and vice versa, (iii) proved the need to make national epidemiological surveys on pediculosis in areas of Mali, (iv) demonstrated by in vitro model that doxycycline has a direct effect on endosymbiont bacteria of louse Candidatus Riesia pediculicola via mycetoma. This last work allowed us to highlight the synergistic efficacy of ivermectin + antibiotics to fight more effectively the infestation of lice and avoid the appearance of resistance. This work was subject of a patent.

El piojo de la cabeza, Pediculus humanus capitis De Geer (Anoplura: Pediculidae) es un problema de salud pública en todo el mundo. Este ectoparásito obligado infesta generalmente a los niños en edad escolar. En este trabajo se investigó la prevalencia de esta enfermedad en los jardines de infantes de la ciudad de Bahía Blanca y los factores de riesgo asociados; además se abordaron alternativas de control para este insecto por medio de insecticidas botánicos. De un total de 220 alumnos examinados (125 niñas y 95 varones), 94 mostraron pediculosis. La prevalencia general de la infestación de piojos fue de 42,7%. La pediculosis fue más frecuente en las niñas (53,6%) que en los varones (28,4%) y en pelos medianos, largos y muy largos. No se encontraron diferencias entre las clases socio-económicas, lo que indica que los piojos de la cabeza son relativamente comunes en los jardines de infantes de Bahía Blanca. El control mundial de P. h. capitis depende sobre todo de las aplicaciones continuas de insecticidas sintéticos. Aunque estos pediculicidas son aún eficaces, su uso repetido ha dado como resultado el desarrollo de resistencia. Estos problemas corroboran la necesidad de desarrollar un control selectivo. Los compuestos naturales, tales como aceites esenciales se han sugerido como fuentes alternativas para el control de estos insectos. En este trabajo, se evaluó la actividad adulticida y ovicida de los aceites esenciales (AEs) de hojas y frutos de Schinus areira, y hojas de Thymus vulgaris, Aloysia polystachia y Aloysia citriodora en adultos y huevos de P. h. capitis, utilizando bioensayos por exposición a vapores y a superficies tratadas. En los bioensayos por exposición a vapores, todos los AEs mostraron toxicidad frente a ambos estados. Sobre la base de los valores de TV50 (Tiempo de volteo 50), las hojas y frutos de S. areira fueron los más tóxicos en adultos y los AEs de S. areria y T. vulgaris, los más efectivos en huevos. En los bioensayos por exposición a superficies tratadas (sobre papel de filtro), el AE de T. vulgaris fue más tóxico que los demás aceites en huevos y adultos; los AEs de hojas y frutos de S. areira no mostraron efectos en ambos estados. Para introducir un pediculicida en el mercado es necesario analizar la efectividad de los compuestos y el efecto de éstos sobre el ser humano y el ambiente. Teniendo en cuenta estos conceptos, se realizaron pruebas de corrosión / irritación dérmica en conejos albinos de Nueva Zelanda. Los aceites esenciales no produjeron ni corrosión ni irritación en piel. Según los resultados obtenidos en este trabajo, el aceite esencial de hojas de T. vulgaris podría convertirse en una herramienta válida para el control de P. h. capitis, dado que a baja concentración y aplicado durante veintiún minutos, este AE produce un alto efecto de volteo en adultos (seguido de la mortalidad) y toxicidad en huevos. Por otra parte, este AE no genera corrosión / irritación cutánea. / The human head louse, Pediculus humanus capitis De Geer (Anoplura: Pediculidae) is a worldwide public health concern. This human obligate ectoparasite usually infests school age children. The aims of this work were to evaluate the prevalence of head lice and risk factors in kindergarten children from Bahia Blanca city. Otherwise, alternative control methods based on botanic insecticide were investigated. From a total of 220 pupils examined (125 girls and 95 boys), 94 showed pediculosis. The overall prevalence of head lice infestation was 42.7%. Pediculosis was more frequent in girls (53.6%) than in boys (28.4%) and in medium, long and very long hairs. No differences were found between socio-economic classes. This indicated that head lice in kindergarten from Bahía Blanca are relatively common. In recent years, P. h. capitis infestations have been increasing. The main worldwide control of this insect depends on synthetic insecticides continued applications. Although these pediculicides are still effective, their repeated use has sometimes resulted in the development of resistance. Natural compounds such as essential oils have been suggested as alternative sources for insect control agents. The adulticidal and ovicidal activity of essential oils (EOs) from leaves and fruits of Schinus areira and leaves of Thymus vulgaris, Aloysia polystachia and Aloysia citriodora were evaluated against both stages of P.h capitis through fumigant and direct contact bioassays. All EOs showed toxicity against adults and eggs in fumigation tests. On the basis of KT50 (knockdown of 50%) values, leaves and fruits from S. areira were more toxic against adults and S. areria and T. vulgaris against eggs. In filter paper contact bioassay, the EO from T. vulgaris was more toxic than the other ones against eggs and adults. When EO from leaves and fruits of S. areira were evaluated on both stages, no mortality was observed. In order to introduce a new pediculicide product, the effectivity of the compounds and their effects on human being and the environment must be analized. In consequence, dermal corrosion/irritation tests were improved in New Zealand albino rabbits. Results indicated that the EOs not produced these effects. According with the results, the essential oils from leaves of T. vulgaris would be a valid tool for the management of P. h. capitis. This essential oil produces a high knockdown effect in adults (followed by mortality) and toxicity in eggs when is applied for twenty one minutes and at a low concentration. No dermal corrotion/irritation was observed.

Human body lice, Pediculus humanus humanus, and head lice, Pediculus humanus capitis, have been hematophagous ectoparasites of humans for thousands of years. Despite being ecotypes, only body lice are known to transmit bacterial diseases to humans, and it appears that lower humoral and cellular immune responses allow body lice to possess a higher vector competence. We previously observed that the transcription level of the defensin 1 gene was up-regulated only in head lice following oral challenge of Bartonella quintana, a causative agent of trench fever, and also that body lice excreted more viable B. quintana in their feces. In this study, we first investigated this differential immune response by performing RNAi to knockdown defensin 1 by dsRNA injection. B. quintana was orally infected 72 h after injection and proliferation was compared at 2 hours (day 0) and day 4 post-infection. At day 0, bacterial cell numbers increased 1.5-fold in defensin 1 (Def1(-)) knocked down head lice compared with non-knocked down, pQE30-dsRNA injected, head lice control. At day 4, Def1(-) knocked down head lice had 2.55-fold more bacterial cells than control head lice and 1.65-fold greater than body lice, indicating that defensin 1 was active in reducing B. quintana cell number in non-knocked down head lice. Second, the levels of cytotoxic reactive oxygen species (ROS) generated by the epithelial cells of the alimentary tract were measured using two general indictors of ROS in both body and head lice at day 1 and day 4 following B. quintana challenge. Challenged body lice showed a 42% and 34% increase in ROS, whereas head lice showed a 70% and 22% increase at day 1 using CM-H2DCFDA and HPF as general indicators, respectively. On day 4, all challenged lice showed similar ROS levels except for body lice which maintained their ROS levels (40% increase using CM-H2DCFDA). Head lice are likely to have multiple immune and/or non-immune factors that suppress B. quintana proliferation, and the production of sustained ROS levels and/or the single knockdown of Defensin 1 is not enough to increase B. quintana proliferation in head lice to that seen in body lice.