Em algumas regiões, como nos municípios de Corumbá e Ladário, no Estado de Mato Grosso do Sul, existem evidências ecológicas e epidemiológicas de que Lutzomyia (Lutzomyia) cruzi (Mangabeira, 1938) seja a principal responsável pela transmissão do protozoário Leishmania (Leishmania) infantum Nicolle, 1908 (ou subespécie de L. (L.) infantum chagasi Cunha & Chagas, 1937 segundo alguns autores), agente etiológico da leishmaniose visceral (LV). A ausência de Lutzomyia (Lutzomyia) longipalpis (Lutz & Neiva, 1912), principal vetor do parasito, reforçam esta hipótese. Este estudo teve por objetivo avaliar os parâmetros e estimar a capacidade vetorial de Lu. cruzi para L. (L.) infantum e Leishmania (Leishmania) amazonensis Lainson & Shaw, 1972. Para este último, apenas foram avaliados os parâmetros, sem a estimativa numérica da capacidade vetorial. A avaliação da capacidade vetorial foi realizada a partir de experimentos laboratoriais (infecção experimental) e de campo (atratividade aos flebotomíneos). Por intermédio da infecção experimental de Lu. cruzi pelo parasito, foi possível estimar a expectativa de sobrevida diária de fêmeas infectadas (estimativa vertical e laboratorial), avaliar o período de incubação extrínseco do parasita e obter duração do ciclo gonotrófico. Para a avaliação da competência vetorial do inseto, foram realizadas tentativas de transmissão experimental e natural de Leishmania, a partir de fêmeas provenientes de colônia cujos indivíduos foram alimentados durante o xenodiagnóstico e de fêmeas selvagens capturadas em campo, respectivamente. A distribuição sazonal de Lu. cruzi foi avaliada por meio da instalação semanal de armadilhas luminosas no peridomicílio de cinco residências na área urbana do Município de Corumbá. Variáveis meteorológicas obtidas junto ao Centro de Monitoramento do Tempo, do Clima e dos Recursos Hídricos de Mato Grosso do Sul, índices radiométricos calculado a partir de imagens de resolução espacial (GeoEye) e o percentual de cobertural vegetal foram utilizados neste estudo. Os resultados obtidos permitiram estimar a capacidade vetorial de Lu. cruzi para L. (L.) infantum, que foi de 0,24, ou seja, espera-se que a população de fêmeas da área produzam 0,24 novas infecções viii por dia de exposição de uma infecção. A competência vetorial de Lu. cruzi para L. (L.) infantum e L. (L.) amazonensis, via picada, foi demonstrada por meio de transmissão natural e experimental dos parasitos, respectivamente. Também foi identificada a infecção natural de Lu. cruzi por L. (L.) amazonensis. Com relação à distribuição mensal, embora não tenha sido observada a presença de associação entre essas espécies e as variáveis ambientais de vegetação e clima, foi possível observar picos elevados populacionais na estação chuvosa e picos menores na estação seca. O padrão da distribuição sazonal das espécies de flebotomíneos demonstrado neste estudo foi determinado basicamente pelos espécimes de Lu. cruzi capturados, uma vez que eles representam 93,94 por cento . A variação mensal demonstrou que a espécie Lu. cruzi tem grande plasticidade, tendo sido observada em todos os meses de coleta. / In some regions such as in the municipalities of Corumbá and Ladário in Mato Grosso do Sul state, there are ecological and epidemiological evidence that Lutzomyia (Lutzomyia) cruzi (Mangabeira, 1938) is the vector of Leishmania (Leishmania) infantum Nicolle, 1908 (or subspecies of L. (L.) infantum chagasi Cunha & Chagas, 1937 according to some authors), the etiologic agent of visceral leishmaniasis (VL). The absence of Lutzomyia (Lutzomyia) longipalpis (Lutz & Neiva, 1912), the main vector of the parasite, supports this hypothesis. This study aimed to evaluate the parameters and estimate the vectorial capacity of Lu. cruzi for L. (L.) infantum and Leishmania (Leishmania) amazonensis Lainson & Shaw, 1972. For the latter, only parameters was evaluated without numerical estimation of the vectorial capacity. The evaluation of the vectorial capacity was carried out from laboratory experiments (experimental infection) and field (attractiveness to sandflies). Through experimental infection by the parasite, it was possible to estimate the expected daily survival of infected females (vertical and laboratory estimate), evaluate the extrinsic incubation period of the parasite and get the length of gonotrophic cycle. To evaluate the insect vector competence, attempts have been made of experimental and natural transmission of Leishmania from females from colony whose subjects were fed for xenodiagnosis and wild females captured in the field, respectively. Monthly and seasonal distribution of Lu. cruzi was evaluated by weekly installation of light traps in the peridomicile of five residences in the urban area of the Municipality of Corumbá. Meteorological variables obtained from the Weather Monitoring Center, Climate and Water of Mato Grosso do Sul Resources, radiometric indices calculated from spatial resolution images (GeoEye) and the percentage of plant cobertural were used in this study. Results allowed estimating the vectorial capacity of Lu. cruzi for L. (L.) infantum, which was 0.24, i.e., it is expected that the female population in the region produce 0.24 new infections per day of exposure to an infection. Vector competence of Lu. cruzi for L. (L.) infantum and L. (L.) amazonensis by biting, was demonstrated by natural and experimental transmission of both parasites, respectively. Natural infection of Lu. cruzi by L. (L.) amazonensis was identified. Regarding the monthly x distribution, there was no significant association between of sandflies and the environmental and climate variables. It was observed high peaks population in the rainy season and lower peaks in the dry season. The pattern of seasonal distribution of species of sand flies demonstrated in this study was determined primarily by Lu. cruzi specimens, since this species represent 93.94 per cent of the total captured. The monthly change showed that Lu. cruzi species has great plasticity and has been observed in all months of collection.

No início de 2010, uma nova riquetsiose foi descrita em um paciente humano, que foi infestado por carrapato em Barra do Una, no litoral sul do Estado de São Paulo. Técnicas moleculares indicaram que esta nova doença foi causada por uma nova cepa de riquétsia, que foi denominada de Rickettsia parkeri cepa Mata Atlântica. Estudos mais recentes demonstraram que 10 a 15% dos carrapatos Amblyomma ovale, coletados em áreas de Mata Atlântica nos estados de São Paulo (incluindo a área do caso índice da infecção humana em Barra do Una) e Santa Catarina estavam infectados com R. parkeri cepa Mata Atlântica. Desta forma, o presente estudo iniciou-se a partir de fêmeas ingurgitadas de A. ovale, coletadas de cães naturalmente infestados em Barra do Una. No laboratório, foi constatado por PCR que parte dessas fêmeas (6,25%) estavam naturalmente infectadas por R. parkeri cepa Mata Atlântica; os ovos dessas fêmeas foram utilizados para formar uma colônia de A. ovale naturalmente infectada por R. parkeri. Ovos de fêmeas não infectadas, foram utilizados para formar uma colônia não infectada. As duas colônias foram estudadas de forma paralela no laboratório, visando analisar e quantificar a transmissão transestadial e transovariana de R. parkeri cepa Mata Atlântica e a competência vetorial do A. ovale. As infestações por larvas foram realizadas em roedores (Calomys callosus), enquanto ninfas e adultos foram alimentados em Oryctolagus cunicullus (coelho doméstico). Amostras de 10 indivíduos de cada uma das fases (larvas, ninfas e adultos F1, ovos, larvas e ninfas F2) foram testadas individualmente por um sistema de taqman real-time PCR, para presença de Rickettsia spp. Os soros sanguíneos de todos animais infestados foram testados por imunofluorescência indireta com antígeno de R. parkeri, no dia zero e 21 dias após a infestação por carrapatos, a fim de verificar soroconversão para antígenos de Rickettsia. Os resultados obtidos demonstraram 100% de transmissões transestadial (larva para ninfas e ninfas para adultos) e transovariana de R. parkeri em A. ovale, uma vez que todas as amostras de ovos, larvas, ninfas e adultos do grupo infectado foram positivas na PCR. Larvas e ninfas de A. ovale demonstraram alta competência vetorial, pois todos animais infestados por esses estágios infectados soroconverteram para R. parkeri. Por outro lado, adultos foram parcialmente competentes, pois apenas metade dos coelhos soroconverteu após ser infestada com carrapatos adultos infectados. Nenhum carrapato do grupo controle foi positivo na PCR, assim como nenhum animal deste grupo soroconverteu para R. parkeri. Fêmeas infectadas por R. parkeri cepa Mata Atlântica tiveram parâmetros reprodutivos inferiores aos das fêmeas não infectadas, indicando algum efeito deletério da infecção por este agente sobre os carrapatos. Os resultados sugerem a importância do carrapato A. ovale na epidemiologia desta nova riquetsiose brasileira, assim como sugerem uma capacidade vetorial de A. ovale para R. parkeri cepa Mata Atlântica, uma vez que este carrapato é frequentemente encontrado infestando humanos no bioma de Mata Atlântica. / In early 2010, a novel rickettsiosis was described in a human patient that had been infested by a tick in Barra do Una, southern coast of the state of São Paulo, Brazil. Molecular tests indicated that the disease was caused by a new rickettsial strain, named Rickettsia parkeri strain Atlantic rainforest. More recent studies demonstrated that 10 to 15% of Amblyomma ovale ticks, collected in Atlantic rainforest areas in the states of São Paulo (including the human index case area in Barra do Una) and Santa Catarina were infected with R. parkeri strain Atlantic rainforest. Within this context, the present study started with A. ovale engorged females collected from naturally infested dogs in Barra do Una. In the laboratory, it was shown by PCR that part of these females (6.25%) were naturally infected with R. parkeri strain Atlantic rainforest; the eggs of these females were used to form a lab colony of A. ovale, naturally infected by R. parkeri. Eggs laid by uninfected females were used to form an uninfected tick colony. Both colonies were evaluated in parallel in the lab, aiming to verify and quantify the transstadial and transovarian transmissions of R. parkeri strain Atlantic rainforest in A. ovale ticks, and the vector competence of the different parasitic stages of this tick. Larval infestations were done on rodents (Calomys callosus), while nymphal and adult infestations were done on rabbits (Oryctolagus cunicullus). Samples of 10 individuals of each tick stage (F1 larvae, nymphs and adults; F2, eggs, larvae, and nymphs) were tested individually by a taqman real-time PCR targeting the genus Rickettsia. Blood serum samples from all infested animals were tested through immunofluorescence assay employing R. parkeri antigens, on zero and 21 days post tick infestation, in order to verify seroconversion to rickettsial antigens. The results demonstrated 100% of transstadial (larvae to nynphs; nymphs to adults) and transovarian transmissions of R. parkeri in A. ovale ticks, since all egg, larval, nymphal, and adult samples from the infected colony were PCR-positive. A. ovale larvae and nymphs demonstrated high vector competence because all animals infested by these tick infected stages seroconverted to R. parkeri. On the other hand, adult ticks were partially competent since only half of the animals seroconverted after being infested by infected adult ticks. None tick of the uninfected control colony was PCR positive, as well as no animal from this group seroconverted to R. parkeri. Tick females infected by R. parkeri strain Atlantic rainforest had lower reproductive parameters than uninfected females, indicating some deleterious effect of the infection on these ticks. The results suggest an important role of A. ovale ticks in the epidemiology of this novel Brazilian rickettsiosis, and also suggest that A. ovale are capable to transmit R. parkeri strain Atlantic rainforest under natural conditions, since this tick is frequently found infesting humans on the Atlantic rainforest biome.

Dirofilaria immitis Leidy (dog heartworm) is a life-threatening parasite transmitted by mosquitoes to domestic dogs. Endemic in the eastern United States, cases have become more prevalent over the last few decades. While prevalence in California is generally low, Lake and San Joaquin Counties have reported rates comparable to the East Coast at 3.73% and 0.71%(CAPC 2017), respectively. Aedes sierrensis is thought to be responsible for transmission in California, but in some cases, it exists in inadequate quantities and temporal ranges to explain parasite activity. Based on Huang et al. (2013) and Tran (2016), bloodfeeding patterns, and other vector criteria, Culex pipiens complex and Culiseta incidens were chosen to evaluate for vector competence. Female field-caught mosquitoes were reared, infected (2.5-5 mff/μl), and decapitated at 15, 18, or 21 days post infection (dpi). Cs. incidens was reluctant to feed using an artificial feeding system and will require additional trials. On the contrary, trials on Ae. sierrensis and Cx. pipiens complex were both completed successfully. Both species were determined to be competent vectors of D. immitis. Based on our findings, more than half of Ae. sierrensis females produced emerging L3s by 21 dpi, while Cx. pipiens complex never produced L3s in more than 5% of females. In conjunction with other factors such as the detection of D. immitis in wild mosquitoes, host-seeking preferences for domestic dogs, and appropriate temporal overlap, this suggests that both Ae. sierrensis and Cx. pipiens complex may play central roles in Lake or San Joaquin Counties, CA when abundant. Targeted control efforts are necessary to reduce the incidence of canine heartworm in these areas. While Lake and San Joaquin Counties, CA were the focus of this study, our results may be applicable to the western United States when these species are relevant.

Using reverse genetics, we analyzed a chikungunya virus (CHIKV) isolate of the Indian Ocean lineage lacking direct repeat (DR) elements in the 3′ untranslated region, namely DR1a and DR2a. While this deletion mutant CHIKV-∆DR exhibited growth characteristics comparable to the wild-type virus in Baby Hamster Kidney cells, replication of the mutant was reduced in Aedes albopictus C6/36 and Ae. aegypti Aag2 cells. Using oral and intrathoracic infection of mosquitoes, viral infectivity, dissemination, and transmission of CHIKV-∆DR could be shown for the well-known CHIKV vectors Ae. aegypti and Ae. albopictus. Oral infection of Ae. vexans and Culex pipiens mosquitoes with mutant or wild-type CHIKV showed very limited infectivity. Dissemination, transmission, and transmission efficiencies as determined via viral RNA in the saliva were slightly higher in Ae. vexans for the wild-type virus than for CHIKV-∆DR. However, both Ae. vexans and Cx. pipiens allowed efficient viral replication after intrathoracic injection confirming that the midgut barrier is an important determinant for the compromised infectivity after oral infection. Transmission efficiencies were neither significantly different between Ae. vexans and Cx. pipiens nor between wild-type and CHIKV-∆DR. With a combined transmission efficiency of 6%, both Ae. vexans and Cx. pipiens might serve as potential vectors in temperate regions.

Alphaviruses are a group of medically relevant arthropod-borne viruses (arboviruses) belonging to the Togaviridae family that are maintained by mosquito vectors. These zoonotic viruses are clustered into two groups: New World and Old World, depending on their geographical origin/distribution and clinical manifestations. Both of these groups cause disease symptoms of an acute febrile illness; however, each group has a distinct, hallmark disease symptom; New World alphaviruses, such as Eastern, Western, and Venezuelan equine encephalitis viruses (EEEV, WEEV, and VEEV, respectively), present with severe encephalitis while Old World alphaviruses, such as Sindbis, chikungunya, and Mayaro viruses (SINV, CHIKV, and MAYV, respectively) present with an incapacitating polyarthralgia that can persist for years following initial infection. To date, the most effective means of controlling these arboviral infections is through mosquito control programs. However, these programs have crucial limitations in their effectiveness; therefore, novel approaches are necessary to control the spread of these crippling pathogens and lessen their disease burden. Given the close phylogenetic and antigenic relationship between MAYV and CHIKV, we hypothesized that prior CHIKV immunity may affect the outcome of MAYV disease and/or limit its emergence in humans. Our work has shown that anti-CHIKV neutralizing antibodies can provide cross-protective immunity against MAYV disease. Alongside these studies, we have characterized the potency of a camelid-derived single-domain antibody (sdAb) that neutralizes a breadth of alphaviruses, including CHIKV and MAYV. With these data, we have designed and generated transgenic Aedes aegypti mosquitoes that express two anti-CHIKV sdAbs to target infection, dissemination, and transmission of MAYV and CHIKV within this deadly vector. These findings are particularly significant because they highlight the ability to co-target two emerging alphaviruses that are crippling public health and obliterating quality of life around the globe within a single defense strategy. / Doctor of Philosophy / Alphaviruses are arthropod-borne viruses (arboviruses) belonging to the Togaviridae family that infect millions of people annually via the bite of female mosquitoes. These viruses are major public health threats due to their ability to infect humans and animals and infections resulting in a range of debilitating diseases. Viruses within this genus are clustered into two groups: Old World and New World, based on geographical origin and distribution. While New World alphaviruses are known for inducing severe encephalitis (i.e., swelling in the brain), a hallmark symptom of the Old World alphaviruses is the development of incapacitating polyarthralgia (i.e., widespread joint pain) that can persist for years following initial infection. To date, the most effective means of combatting these viruses is through mosquito control programs. However, these programs have crucial limitations in their effectiveness; therefore, novel approaches are necessary to control the spread of these crippling pathogens. Given the close genetic relationship between chikungunya virus (CHIKV) and Mayaro virus (MAYV), our research has focused on harnessing cross-reactive immunity between these emerging alphaviruses. We discovered this cross-reactivity provides protective immunity to both viruses (i.e., CHIKV and MAYV) after exposure to only one (i.e., CHIKV) of the viruses. Next, we characterized the potency of a small, single-domain antibody (sdAb) to neutralize a breadth of alphaviruses, including CHIKV and MAYV. With these data, we have designed and generated transgenic Aedes aegypti mosquitoes that express this sdAb to target both CHIKV and MAYV within this deadly mosquito vector. These findings are particularly significant because they provide the foundation for a novel approach to controlling and preventing outbreaks of these emerging alphavirus pathogens that obliterate quality of life in public health settings around the globe.

Depuis la fin du 19ème siècle, les épidémies dues aux arbovirus constituent un problème de santé publique majeur en Nouvelle-Calédonie et dans la région Pacifique. Ces cinq dernières années, la fréquence des épidémies de dengue a augmenté et l’introduction des virus du chikungunya et du Zika (ZIKAV) a démontré que cette région du monde pouvait être un hot spot d’émergence des arboviroses. Ces trois virus sont transmis par des moustiques du genre Aedes dont le principal vecteur de la région Pacifique est Aedes aegypti. Mis à part des données sur l’épidémiologie de la dengue dans la région, peu d’informations étaient alors disponibles sur les vecteurs ou sur leurs capacités à transmettre les arbovirus. Or ces données sont cruciales pour mieux comprendre l’incidence particulière de ces épidémies dans la région.Dans ce travail de thèse, nous avons tout d’abord caractérisé génétiquement le vecteur Ae. aegypti de la région Pacifique et montré une différence génétique modérée de ce vecteur à l’échelle régionale. Nous avons ensuite, pour la première fois, évalué la compétence vectorielle d’Ae. aegypti pour les virus de la dengue 1 (DENV-1) et du ZIKAV. Les résultats obtenus montrent une faible transmission du DENV-1 et des taux de transmission hétérogènes du ZIKAV en fonction des différentes lignées virales.Les interactions entre le génotype du vecteur et le génotype viral semblent donc revêtir une importance particulière dans notre contexte. Les résultats obtenus au cours de ce travail doctoral devraient permettre une meilleure évaluation du risque de survenue d’une épidémie d’arbovirose en Nouvelle-Calédonie. / Since the end of the 19th century, epidemics due to arboviruses have been a major public health problem in New Caledonia and the Pacific region. Over the past five years, the incidence of dengue epidemics has increased and the introduction of the chikungunya and Zika viruses (ZIKAV) has demonstrated that this region of the world is to be considered as a hot spot for the emergence of arboviruses. These three viruses are transmitted by mosquitoes of the genus Aedes, whose main vector in the Pacific region is Aedes aegypti. With the exception of some data concerning the dengue virus epidemiology in the region, little was known about vectors or on their ability to transmit arboviruses. These data are crucial to increase our knowledge about the specific appearance of these epidemics in the region.During my PhD, I first genetically characterized the vector Ae. aegypti from the Pacific region and demonstrated a moderate but significant genetic differentiation. We were also the first to evaluate Ae. aegypti vector competence for dengue virus 1 (DENV-1) and for different ZIKAV strains. The results have shown a low transmission efficiency for DENV-1 and heterogeneous results for the ZIKAV transmission, these differences were linked to the ZIKAV genetic lineage.The interactions between the vector genotype and the viral genotype seem to be particularly important in our context. The results obtained during this PhD work should allow a better assessment of the risk of an arbovirus outbreak in New Caledonia as well as the development of prevention strategies.

La peste porcine africaine (PPA) est une maladie hémorragique contagieuse dévastatrice pour l’élevage porcin pour laquelle aucun traitement ni vaccin ne sont disponibles. Cette infection est due à un virus à ADN, unique membre de la famille des Asfarviridae, qui se transmet directement entre suidés ou via un vecteur, la tique du genre Ornithodoros. Le rôle de ces tiques dans le cycle épidémiologique de la PPA consiste principalement à maintenir le virus dans les populations de suidés sauvages en Afrique. Elles ont aussi été identifiées à l’origine de certains cas de résurgence de la maladie dans des bâtiments d’élevage porcin, notamment dans la péninsule ibérique, lors des années 1970-80. La PPA, éradiquée fin des années 1980 en Europe (à l’exception de la Sardaigne), a été de nouveau introduite en 2007 d’abord en Géorgie pour progresser jusqu’à atteindre l’Est de l’Union Européenne. La question de la compétence vectorielle des tiques Ornithodores pour le virus de la PPA et des déterminants qui influencent cette compétence est posée dans l’évaluation des risques d’endémisation et/ou de dispersion de la maladie en Europe et ailleurs. Le premier chapitre de cette thèse vise à caractériser la compétence vectorielle des tiques Ornithodores pour le virus de la PPA et faire ressortir les patrons généraux qui la qualifient. Pour cela, a été réalisée une revue systématique des études ayant testé la compétence vectorielle d’une ou plusieurs espèces de tiques pour une ou plusieurs souches virales de PPA durant ces 50 dernières années. Au final, il en ressort une forte variabilité de résultats selon les couples tique-virus. En outre, il semble difficile de comparer ces résultats et d’établir des « profils types » du fait de l’évaluation partielle de la compétence vectorielle pour de nombreux couples tique-virus et de la diversité des méthodologies utilisées pour tester et mesurer la compétence. Pour autant chaque modalité d’étude révèle une partie des mécanismes et des adaptations auxquels sont soumis les couples tique–virus et suggère l’effet de certains déterminants dont deux sont traités dans les deux autres chapitres de la thèse. Le second chapitre de la thèse traite de l’adaptation tique-virus, par l’étude expérimentale de l’infection des tiques O. erraticus, O. porcinus et O. moubata à l’aide de deux souches de génotype II du virus de la PPA, et par un essai de transmission du virus des tiques aux porcs. Des souches du génotype II ont été choisies car ce génotype circule actuellement en Europe et risque d’infecter les tiques européennes O. erraticus s’il se propage jusqu’en péninsule ibérique. Alors qu’O. erraticus est capable de s’infecter et de transmettre différentes souches virales du génotype I, sa compétence à transmettre la souche Georgia2007/1 (génotype II) n’a pour l’instant pas été démontrée. Toutefois, nos études suggèrent que les résultats de compétence dépendent aussi des conditions d’expérimentation telles que la nature des colonies de tiques utilisées ou encore le titre viral utilisé pour infecter les tiques. Le dernier chapitre de la thèse porte sur l’effet de la salive de tique sur l’étape de transmission du virus de la PPA par la tique au porc. Durant le repas de sang, la salive est un élément essentiel qui va permettre l’accroche et le gorgement durable de la tique sur son hôte, avec des propriétés immuno-modulatrices importantes agissant directement sur l’hôte. Ainsi a été réalisée une étude expérimentale in vivo faisant intervenir la tique O. porcinus et le virus Ambat02 (génotype II) et testant l’effet local et systémique chez le porc d’un extrait de glandes salivaires de tique co-inoculé ou non avec le virus de la PPA, versus la piqûre naturelle de tiques non infectées. Les résultats de cette expérience nous montrent que la salive de tique est capable de moduler au niveau local le recrutement de cellules immunitaires dans la peau du porc et potentiellement influencer l’infection locale chez le porc. / African swine fever (ASF) is a contagious hemorrhagic disease with disastrous financial consequences for pig industry, as no vaccine or treatment exists. This infection is caused by a DNA virus, only member of the Asfarviridae family that can be directly transmitted between swine or by a non-compulsory vector, the Ornithodoros tick. Ornithodoros ticks play a role in the persistence of the disease within wild and domestic suids in Africa. They were also involved in resurgences of outbreaks in some pig farms in the Iberian Peninsula in 1970-1980. ASF, eradicated in Europe at the end of the 1980’s except in Sardinia, was reintroduced in Georgia in 2007 then spread towards the Eastern European Union. The question of the tick vector competence for ASF virus (ASFV) and its related determinants is of importance in the risk assessment of endemisation/spread of the disease in Europe or elsewhere.The first chapter of this thesis aims to characterize Ornithodoros tick vector competence for ASFV and to highlight a common pattern to qualify it. For this purpose, a systematic review of the studies carried out on the vector competence of one or more tick species for one or more ASFV, was performed on the last 50 years publications. A high variability of the results obtained for different couples “tick-virus” was highlighted. As most of the papers describe partial evaluation of the vector competence and because of the high number of methods used to perform these assessments, it was definitively very difficult to compare these results, and to propose common patterns. However, each of these studies revealed a part of the mechanisms that participated to the adaptation in the couple “tick-virus”, and suggested the importance of different determinants, out of them, two were experimentally assessed as described in the two other chapters.The second chapter of this thesis describes the adaptation “tick-virus” through the experimental infection of three different ticks, O. erraticus, O. porcinus and O. moubata by two ASFV strains belonging to the genotype II. O erraticus’s competence is known for ASFV strains belonging to the genotype I but has never demonstrated the ASFV Georgia 2007/1 strain (genotype II) and currently circulating in Europe. However, the experiments we performed, suggest that many experimental conditions could influence the results obtained on vector competence as the tick colony or the virus dose used for the tick infection.The third chapter describes the effect of the tick saliva on the ASFV transmission from the tick to the pig. Tick saliva contains important immunomodulatory molecules that interfere with the pig immune system permitting complete engorgement of the tick on its host. The host-vector and pathogen interactions were studied through an in vivo experimentation involving pig, O porcinus tick and ASFV Ambat02 strain (genotype II). The local and systemic effects on the pig immune responses were assessed with the ASFV alone or combined with tick gland extract, versus a healthy tick bite. Data analysis highlighted the tick saliva role on skin immune cell recruitment and its potential effect on local infection.

Le paludisme demeure un problème de santé majeur en Afrique subsaharienne. Le nombre limité d'antipaludiques, l’apparition de résistances et l’absence d’un vaccin efficace, font de la lutte anti-vectorielle (LAV) la principale stratégie préventive de cette maladie. Les méthodes actuelles de LAV visant à limiter ou à interrompre le développement du parasite chez le moustique vecteur, il est donc nécessaire d’améliorer notre compréhension des interactions entre le vecteur Anopheles, son environnement et le parasite Plasmodium. A Madagascar, Anopheles gambiae s.l. et Anopheles funestus sont les vecteurs majeurs de Plasmodium falciparum et de Plasmodium vivax. Anopheles mascarensis, espèce endémique, peut également être un vecteur important. Dans ce contexte, l’objectif premier de ma thèse a été d’approfondir les connaissances sur An. mascarensis à travers une revue. Les données collectées plaident davantage qu’An. mascarensis est un complexe d'espèces et permettent de poser les bases pour une analyse moléculaire ciblée. En parallèle, j’ai contribué à la mise en place de la première plateforme expérimentale de Madagascar pour infecter des anophèles par P. falciparum et P. vivax, afin d’évaluer leur compétence vectorielle. Enfin, en associant entomologie et immuno-parasitologie, nous avons analysé la contribution des vecteurs à la transmission du paludisme dans deux villages adjacents. L’ensemble des travaux réalisés durant de ma thèse contribue à une meilleure connaissance de la diversité de la transmission du paludisme à Madagascar. De plus, la mise en place de la plateforme expérimentale d’infection permettra l’analyse de la compétence des populations d’anophèles vecteurs. / Malaria remains a major health concern in sub-Saharan Africa. The limited number of antimalarial drugs, the emergence of resistances and the lack of an effective vaccine, make vector control the main preventive strategy for this disease. Current methods of vector control aim at limiting or interrupting parasite development in the vector mosquito. It is therefore necessary to improve our understanding on interactions between the Anopheles vector, its environment and the parasite Plasmodium. In Madagascar, Anopheles gambiae s.l. and Anopheles funestus are the major vectors of Plasmodium falciparum and Plasmodium vivax. Anopheles mascarensis, an endemic species, may also be an important vector. In this context, the main objective of my PhD was to deepen the knowledge on An. mascarensis through a review. The data collected indicate that An. mascarensis is a complex of sibling species. I could thus provide the foundation for targeted molecular analysis. In parallel, in order to evaluate their vector competence, I contributed in a major way to the establishment of the first experimental platform of Madagascar to infect anopheline mosquitoes by P. falciparum and P. vivax. Finally, combining entomology and immuno-parasitology, we analysed the contribution of vectors to malaria transmission in two neighbouring villages. All the work done during my PhD contributes to a better knowledge of the diversity of malaria transmission in Madagascar, especially on the effective contribution of the different vector species. In addition, the establishment of the experimental platform for infections will further allow the analysis of the competence of vector Anopheles populations.

Zika (ZIKV), La Crosse (LACV), and Cache Valley (CVV) viruses are mosquito-vectored diseases that cause significant morbidity and mortality in humans and animals. Transmission of these viruses are dependent on numerous factors including vector competence and the effects of mosquito-virus interactions. We conducted vector competence studies of local Aedes and Culex mosquitoes for ZIKV and CVV, and found that all Aedes mosquitoes were competent for CVV and only Aedes albopictus and Aedes japonicus were competent for ZIKV. Vector competence for CVV was dose-dependent, where mosquitoes orally infected with high titers developed higher transmission rates. We also found that vector competence for ZIKV was limited by midgut and salivary gland barriers. Second, we looked at the effects of LACV and ZIKV infection on repellent response in Aedes mosquitoes and found that infected mosquitoes were refractory to low concentrations of DEET, picaridin, and PMD. Increasing concentrations of the repellents to ≥10% was able to increase percent protection (%p) against infected and uninfected mosquitoes. Lastly, we determined the effects of ZIKV and LACV infection on oxidative stress and glutathione-S-transferase (GST) activity in Aedes albopictus. Virus infection had no effect on oxidative stress, but GST activity was significantly different for mosquitoes 3-days post-exposure. We found that oxidative stress levels and GST activity had an inverse relationship for infected and uninfected mosquitoes, where oxidative stress decreased and GST activity increased over the 10-day test period. This indicates that GSTs may aid in controlling byproducts of oxidative stress. The results from this entire study identified competent vectors for emerging arboviruses and demonstrated the behavioral and physiological effects of virus infection in the mosquito vector. / Doctor of Philosophy / Zika (ZIKV), La Crosse (LACV), and Cache Valley (CVV) viruses are transmitted by mosquitoes and can make humans and animals very sick. There are many biological factors that determine if a mosquito can transmit a virus and these viruses can change the biology of a mosquito. We conducted laboratory studies to see if Aedes and Culex mosquitoes can transmit ZIKV and CVV. We found that all Aedes mosquitoes were able to transmit CVV and only the Asian tiger mosquito and Asian rock pool mosquito were able to transmit ZIKV. Mosquitoes infected with high amounts of CVV developed higher transmission rates. We also found that transmission of ZIKV was limited by barriers in the mosquito midgut and salivary glands. Second, we looked at the effects of LACV and ZIKV infection on how Aedes mosquitoes respond to repellents and found that infected mosquitoes were less sensitive to low concentrations of DEET, picaridin, and PMD. Increasing concentrations of the repellents to 10% or higher was able to provide adequate protection against infected and uninfected mosquitoes. Lastly, we determined the effects of ZIKV and LACV infection on oxidative stress and glutathione-S-transferase (GST) activity in the Asian tiger mosquito. Virus infection did not change oxidative stress, but GST activity was higher in infected mosquitoes tested after 3 days after infection. We found that oxidative stress decreased and GST activity increased over the 10-day test period. This indicates that GSTs may help control damaging products from oxidative stress. The results from this entire study identified what mosquitoes were able to transmit emerging mosquito-borne viruses and demonstrated the biological effects of virus infection in the mosquitoes.

Einleitung: Das West Nil-Virus (WNV) und das Usutu-Virus (USUV) zirkulieren seit vielen Jahren in Europa und sind auch in Deutschland endemisch geworden. Beide Viren können schwere Erkrankungen in Vögeln auslösen. Zudem kann insbesondere WNV auch zu schweren neurologischen Erkrankungen bei Menschen und Pferden führen, und unentdeckte WNV-Infektionen sind ein Risiko für die Sicherheit von Blutspenden. WNV und USUV werden von Stechmücken als biologische Vektoren übertragen, wobei sich verschiedene Mückenspezies in ihrer Vektorkompetenz unterscheiden können. Die Kenntnis über die Vektorkompetenz von Mückenspezies ist essentiell für die effiziente Überwachung und Bekämpfung dieser Viren. Weitgehend unbekannt ist jedoch, welche Auswirkungen Ko-Infektionen mit WNV und USUV auf die Vektorkompetenz von Stechmücken haben. Ziele der Untersuchungen: Ziel der ersten Studie war es, die Vektorkompetenz der bislang wenig untersuchten Mückenspezies Aedes punctor für WNV zu bestimmen. Mit der zweiten Studie sollten Mono- und simultane Ko-Infektionen mit WNV und USUV in verschiedenen Stechmückenarten (Culex pipiens Biotyp pipiens, Culex pipiens Biotyp molestus, Aedes vexans) durchgeführt werden, um die Auswirkungen von Ko-Infektionen auf die Übertragung beider Viren zu bestimmen. Tiere, Material und Methoden: Die für die Versuche verwendeten Stechmücken wurden entweder in Deutschland gesammelt oder stammten aus den Laborkolonien am Friedrich-Loeffler-Institut. Die Infektionen erfolgten oral über Blut, welches ein oder beide Viren enthielt und über Wattestäbchen angeboten wurde. Blutgesogene Weibchen wurden über einen definierten Zeitraum unter definierten Umweltbedingungen inkubiert. Nach Ablauf der Inkubationszeit wurden die noch lebenden Tiere durch das Entfernen der Beine und Flügel immobilisiert, um die Gewinnung von Speichel zu ermöglichen. Ein Teil der Speichelprobe wurde auf eine Zellkultur gegeben, um infektiöse Viruspartikel nachzuweisen. Zur Bestimmung der Infektion, Dissemination und potenzieller Übertragung wurden die Körper, die Beine und Flügel, die Speichelproben sowie der Überstand der Zellkultur mit einer quantitativen Reverse-Transkriptase-Polymerase-Kettenreaktion (RT-qPCR) auf virale RNA untersucht. Im Falle der Ko-Infektionsstudie wurden zeitgleich Mono-Infektionen durchgeführt und die Ergebnisse verglichen, um potenzielle Veränderungen in Empfänglichkeit oder Übertragung feststellen zu können. Ergebnisse: In der ersten Studie zeigte sich, dass Ae. punctor nicht vektorkompetent für WNV ist. Von insgesamt 155 untersuchten Weibchen waren nur 7 Tiere mit WNV infiziert. In den Speichelproben wurden weder infektiöse Viruspartikel noch virale RNA nachgewiesen. In der zweiten Studie konnte gezeigt werden, dass sowohl Cx. pipiens Biotyp pipiens als auch Cx. pipiens Biotyp molestus effektive Vektoren für WNV und USUV sein können. Im Gegensatz dazu waren Ae. vexans Weibchen nicht empfänglich für eine Infektion durch WNV oder USUV. In den Ko-Infektionen zeigte sich, dass die Empfänglichkeit für USUV in Cx. pipiens Biotyp pipiens verringert und in Ae. vexans erhöht war. In Cx. pipiens Biotyp molestus waren hingegen keine Unterschiede zwischen Mono- und Ko-infektionen festzustellen. Bei Cx. pipiens Biotyp molestus wurden infektiöse Partikel beider Viren in Speichelproben gefunden, was auf eine potenzielle Ko-Übertragung hindeutet. Schlussfolgerung: Aufgrund der Ergebnisse kann davon ausgegangen werden, dass Ae. punctor und Ae. vexans derzeit keine Rolle bei der Übertragung von WNV oder USUV spielen und daher vorerst bei Überwachungsprogrammen in Deutschland nicht berücksichtigt werden müssen. Für Cx. pipiens Mücken konnte hingegen die Rolle als Hauptvektoren für WNV und USUV durch Infektionsstudien bestätigt werden. Es konnte zudem gezeigt werden, dass die Interaktion zwischen WNV und USUV in der Stechmücke speziesabhängig variiert. Aufgrund dessen ist eine Untersuchung von Ko-Infektionen in weiteren potenziellen Vektorspezies notwendig, um ein besseres Verständnis der Interaktionen zu bekommen. Die Studie zeigt auch, dass unter Umständen auch nicht vektorkompetente Spezies durch eine Ko-Infektion eine Rolle in der Übertragung der Viren spielen könnten. In Gebieten, in denen WNV und USUV sympatrisch zirkulieren, sollte diese Erkenntnis in den Überwachungs- und Bekämpfungsstrategien berücksichtigt werden. Eine potenzielle Ko-Übertragung beider Viren wurde zwar beobachtet, trat innerhalb dieser Studie aber selten auf und scheint daher eher eine geringe Rolle spielen. / Introduction: West Nile virus (WNV) and Usutu virus (USUV) have been circulating in Europe for many years and have also become endemic in Germany. Both viruses can cause severe diseases in birds. In addition, WNV in particular can also lead to severe neurological diseases in humans and horses, and undetected WNV infections pose a risk to the safety of blood donations. Both WNV and USUV are transmitted by mosquitoes as biological vectors, whereby different mosquito species can differ in their vector competence. Knowledge of the vector competence of various mosquito species is essential for efficient surveillance and control of these viruses. What is largely unknown, however, is the impact of co-infections with WNV and USUV on the vector competence of mosquitoes. Objective: The aim of the first study was to determine the vector competence of the mosquito species Aedes punctor for WNV, which has so far been little studied. The second study aimed to perform mono- and simultaneous co-infections with WNV and USUV in different mosquito species (Culex pipiens biotype pipiens, Culex pipiens biotype molestus, Aedes vexans) in order to determine the impact of co-infections on the transmission of both viruses. Animals, material and methods: The mosquitoes used for the experiments were either collected in Germany or were taken from the laboratory colonies at the Friedrich-Loeffler-Institute. Mosquitoes were orally infected via a blood that contained one or both viruses using cotton sticks. Engorged females were incubated over a defined period of time under defined environmental conditions. At the end of the incubation period, surviving animals were immobilized by removing the legs and wings, and saliva was obtained. Part of each saliva sample was placed on cell culture to detect infectious virus particles. To determine infection, dissemination and potential transmission, the bodies, legs and wings, saliva samples and supernatant of the cell culture were analyzed for viral RNA by a quantitative reverse transcriptase polymerase chain reaction (RT-qPCR). During the co-infection study, mono-infections were carried out at the same time as the co-infections and results were compared in order to be able to determine potential changes in susceptibility or transmission. Results: In the first study, Ae. punctor showed to be not susceptible for WNV. Of a total of 155 females examined, only 7 females were found infected. Neither infectious viral particles nor viral RNA was found in saliva samples. In the second study it could be shown that Cx. pipiens biotype pipiens as well as Cx. pipiens biotype molestus can be effective vectors for WNV and USUV. In contrast, Ae. vexans was not susceptible to an infection with WNV or USUV. In Co-infections, it was shown that the susceptibility to USUV was reduced in Cx. pipiens biotype pipiens and increased in Ae. vexans. In Cx. pipiens biotype molestus, however, no differences were found between mono- and co-infections. In Cx. pipiens biotype molestus mosquitoes, infectious particles of both viruses were found in saliva samples, indicating a potential co-transmission by this species. Conclusion: Based on the results, it can be assumed that Ae. punctor and Ae. vexans do not play a role in WNV and USUV transmission and therefore currently do not need to be included in a surveillance in Germany. In contrast, the role of Cx. pipiens mosquitoes as main vectors for WNV and USUV could be confirmed by infection studies. It could also be shown that the interaction between WNV and USUV in the mosquito vector varies and is species dependent. Therefore, an investigation of co-infections in various potential vector species and even different populations is essential to get a better understanding of the interactions between both viruses within the mosquito. The study also showed that, under certain circumstances, non-vector-competent species might also play a role in the transmission of the viruses in the event of a co-infection. Thus, in areas where WNV and USUV are both endemic, surveillance and control programs should take this knowledge into account. Potential co-transmission of both viruses was observed, but was rare in this study and therefore seems to play a rather minor role.