Master of Public Health / Department of Diagnostic Medicine/Pathobiology / Michael W. Sanderson / A zoonotic disease is any disease or infection that is naturally transmissible from vertebrate animals to humans. Over 200 zoonoses have been described (Zoonoses and the Human-Animal-Ecosystems Interface, 2013). Many zoonotic viruses are arboviruses, viruses transmitted by an infected, blood-sucking, arthropod vector (Hunt, 2010). There are several endemic arboviruses in the United States; some foreign arboviruses, such as Rift Valley fever (RVF) virus, are potential bioterrorism agents (Dar, 2013). Arboviruses, both endemic and foreign, threaten public health (Gubler, 2002) and therefore disease surveillance, vector control and public education are all vital steps in minimizing arboviral disease impact in the United States. Mosquito-borne disease threats, such as West Nile virus and Rift Valley fever, are constant concerns in the United States and globally. Current strategies to prevent and control mosquito-borne diseases utilize vector distribution, seasonal and daylight timing, and variation in population numbers. Climate factors, such as availability of still water for development of immature mosquitoes, shade, and rainfall, are known to influence population dynamics of mosquitoes. Using 1995-2011 mosquito population surveillance data from Fort Riley, Kansas, we compared population numbers of Culex tarsalis (Diptera: Culicidae), a vector of several arboviruses including West Nile virus and potentially Rift Valley fever, to a satellite-derived index of climate, the Normalized Difference Vegetation Index (NDVI) anomaly. No correlation between the population numbers and NDVI anomaly was observed, which contrasts with results from similar analyses in other locations. These findings suggest a need for continued investigation into mosquito population dynamics in additional ecological regions of the United States to better describe the heterogeneity of environment-population relationships within and among mosquito species.

The emergence of germ theory during the nineteenth century transformed Western medicine. By the 1870s, public health officials in the American South used germ theory to promote sanitation efforts to control public health crises, such as yellow fever epidemics. Before the discovery of mosquito transmission of yellow fever, physicians of the late nineteenth century believed the disease was spread by a highly contagious germ. Prominent medical practitioners of New Orleans, such as Confederate Army veteran Dr. Joseph Jones, used available scientific knowledge and investigation to attempt to control yellow fever during the Reconstruction period, a period rife with political and racial tension in New Orleans. This paper will analyze nineteenth century Southern medicine through the work of Dr. Joseph Jones and will argue that despite the use of cutting edge scientific methods of the era, the political challenges of the Reconstruction period shaded the public health policies in New Orleans.

La Peste porcine africaine (PPA) est une maladie contagieuse spécifique du porc domestique due au seul arbovirus à ADN identifié à ce jour. Décrite pour la première fois en 1921 au Kenya, la maladie a ensuite diffusé dans de nombreuses régions du monde. Malgré l'isolement de nombreuses souches virales au cours du temps, peu d'études phylogénétiques ont été menées jusqu'ici pour comprendre les relations unissant ces isolats entre eux. Or, la caractérisation est essentielle à la traçabilité des souches et donc à la compréhension de l'épidémiologie de la maladie. De plus, les conditions climatiques et environnementales des principaux pays atteints rendent difficile l'accès, le transport et la conservation de nouvelles souches. Dans cette thèse, un protocole de prélèvement et de conservation du sang a été développé, pour la détection et la caractérisation rapides des souches. Une étude phylogénétique approfondie a été réalisée en utilisant des données de séquences publiques et inédites de virus isolés depuis 1950. Les analyses ont porté sur les gènes B646L, CP204L et E183L. Les analyses phylogénétiques ont utilisé les méthodes de maximum de vraisemblance et d'inférence bayésienne, qui ont permis de proposer une nouvelle nomenclature virale en 35 clusters différents. De plus, une datation des origines du virus a été menée, après avoir éliminé les biais d'analyse dus à une pression de sélection positive et/ou aux recombinaisons. L'horloge moléculaire a permis de déterminer que l'ancêtre commun le plus proche des souches contemporaines (TMRCA) se situait au début du 18ème siècle. / African swine fever (ASF) is a highly lethal disease of domestic pigs caused by the only known DNA arbovirus. It was first described in Kenya in 1921 and since then a substantial number of isolates have been collected worldwide. However, only few phylogenetic studies have been carried out to better understand the relationships between isolates, which is essential for virus traceability and epidemiological understanding of the disease. Access, transport and virus conservation are also complicated by climatic and environmental conditions in affected developing countries. In this thesis, a simple method of blood sampling was developed allowing rapid virus detection and characterization. Comprehensive phylogenetic reconstructions were made using publicly and newly generated sequences of hundreds ASFV isolates of the last 60 years. Analyses focused on B646L, CP204L and E183L genes. Phylogenetic analyses were achieved using maximum likelihood and Bayesian coalescence methods and a new lineage based nomenclature is proposed to designate 35 different clusters. In addition, dating of ASFV origin was carried out from the molecular data sets. To avoid biased diversity, positive selection or recombination events were neutralized. The molecular clock analyses revealed that ASFV strains currently circulating have evolved over 300 years, with a time to the most recent common ancestor (TMRCA) going back to the early 18th century.

A Febre Maculosa Brasileira causada por riquétsias do Grupo Febre Maculosa (GFM) e transmitida por carrapatos ocorre principalmente na Região Sudeste, onde óbitos humanos são registrados. No estado do Rio de Janeiro, a letalidade devido à riquetsiose é alta, mas só recentemente investigações epidemiológicas foram realizadas, e indicaram a participação de novas espécies de ectoparasitas na circulação das riquétsias. O objetivo geral do projeto é avaliar riquétsias em ectoparasitos coletados em áreas de casos humanos de Febre Maculosa, suspeitos, compatíveis ou confirmados, em municípios do estado com focos recentemente comunicados. A detecção e análise de genes riquetsiais indicam a presença de Rickettsia bellii, Rickettsia felis e Rickettsia rickettsii, nos vetores Amblyomma cajennense, Amblyomma dubitatum, Boophilus microplus, Ctenocephalides felis e Ctenocephalides canis, sugerindo ampla distribuição geográfica de riquétsias GFM, nas regiões Serrana, Noroeste Fluminense e Médio Paraíba do estado. / Brazilian spotted fever caused by spotted fever group (SFG) rickettsiae and mainly transmitted by ticks occurs in the southeast, where human deaths are recorded. In the state of Rio de Janeiro, lethality due to rickettsial infection is high, but only recently epidemiological investigations were conducted, and indicated the participation of new species of ectoparasites in rickettsiae circulation. The project\'s overall objective is to evaluate rickettsiae in ectoparasites collected in areas of human suspected, confirmed or compatible cases of spotted fever, in cities of the State with the recently reported outbreaks. The detection and analysis of rickettsial genes indicate the presence of Rickettsia bellii, Rickettsia felis and Rickettsia rickettsii in the vectors Amblyomma cajennense, Amblyomma dubitatum, Boophilus microplus, Ctenocephalides felis and Ctenocephalides canis, suggesting broad geographic distribution of SFG rickettsiae in the regions Serrana, Noroeste Fluminense and Médio Paraíba of the State.

A Febre Maculosa Brasileira (FMB) é uma doença infecciosa causada por Rickettsia rickettsii, transmitida pelo carrapato-estrela Amblyomma sculptum no interior do estado de São Paulo, onde equinos e capivaras são utilizados como sentinelas para FMB por serem considerados hospedeiros primários deste carrapato. Objetivou-se com este trabalho verificar a ocorrência de anticorpos anti-Rickettsia rickettsii em sentinelas clássicos (equinos) e potenciais (ovinos, bovinos e gambás) para FMB que vivem em diferentes ambientes do Campus \"Luiz de Queiroz\", da Universidade de São Paulo, em Piracicaba-SP. De fevereiro de 2017 a janeiro de 2018 foram amostrados 156 hospedeiros, 48 que habitam áreas urbanas, sem a presença ou trânsito de capivaras (15 equinos e 33 gambás), 60 ovinos que frequentam pastagens sem presença de capivaras, mas adjacentes a matas ciliares ocupadas pelos roedores, e 48 que frequentam pastagens por onde transitam capivaras (31 bovinos e seis equinos) ou matas ciliares ocupadas pelos roedores (11 gambás). Quando possível, a amostragem envolveu a coleta de ectoparasitos. O soro obtido após centrifugação do sangue colhido foi analisado em duas etapas, triagem e titulação, pela reação de imunofluorescência indireta (RIFI). Na triagem todas as amostras foram testadas contra R. rickettsii, e consideradas positivas se apresentassem título de anticorpos >= 64. As amostras positivas foram diluídas na etapa de titulação e testadas contra R. rickettsii, R. parkeri, R. bellii, R. ambyommatis e R. rhipicephali para determinação do título máximo de anticorpos para cada espécie. Das 156 amostras testadas, 15 estavam soropositivas, 1/60 ovinos, 1/31 bovinos, 7/21 equinos e 6/44 gambás; os títulos finais variaram de 64 a 4.096. Foi possível determinar o possível antígeno envolvido em reação homóloga (PAERH) em seis amostras, um equino (R. bellii) e quatro gambás e um ovino (R. rickettsii). Foram registrados os carrapatos Amblyomma ovale, Amblyomma dubitatum, Amblyomma sculptum, Dermacentor nitens e Rhipicephalus microplus, e as pulgas Ctenocephalides felis e Siphonaptera: Rhopalopsyllidae cf. Rhopalopsyllus nos hospedeiros amostrados. Conclui-se que equinos e gambás podem ser utilizados como sentinelas para FMB no Campus \"Luiz de Queiroz\", mas os ovinos não. Não foi possível concluir se os bovinos podem ser utilizados com esta função. R. bellii, ou um microrganismo muito semelhante, ocorre na área urbana do Campus \"Luiz de Queiroz\" e é capaz de infectar cavalos. R. rickettsii, ou um microrganismo muito semelhante, ocorre no Campus \"Luiz de Queiroz\" em áreas de permanência e trânsito de capivaras / Brazilian Spotted Fever (BSF) is an infectious disease caused by Rickettsia rickettsii, transmitted by the tick Amblyomma sculptum outside the metropolitan region in the State of São Paulo, where horses and capybaras are used as sentinels for BSF as they are considered primary hosts for this tick. This survey aimed to verify the occurrence of antibodies against Rickettsia rickettsii in sentinels (horses) and potential sentinels (sheep, cattle and opossums) for BSF that lives in different environments of the \"Luiz de Queiroz\" Campus, University of São Paulo, in Piracicaba, SP, Brazil. A total of 156 host were sampled between February of 2017 and January of 2018; 48 that live in urban areas, with no presence or transit of capybaras (15 horses and 33 opossums), 60 sheep that regularly graze on capybara-free pastures adjacent to a riparian forest occupied by these rodents, and 48 that occupy, cross or regularly graze on pastures (31 cows and six horses) or riparian forests (11 opossums) that are areas used by capybaras. Whenever possible, host sampling included ectoparasites collection. Sera obtained after centrifugation of the collected blood was analyzed in two steps, screening and titration, by the indirect immunofluorescence assay technique (IFA). All samples were tested against R. rickettsii during the screening, and those that presented antibodies titers >= 64 were considered positive. Positive samples were diluted during titration and tested against R. rickettsii, R. parkeri, R. bellii, R. ambyommatis and R. rhipicephali for determination of maximum antibodies titers for each species. Of the 156 tested samples, 15 were seropositive, 1/60 sheep, 1/31 cows, 7/21 horses and 6/44 opossums; antibodies endpoint titers ranged from 64 to 4.096. Possible antigen involved in a homologous reaction (PAIHR) was determined for six samples, one horse (R. bellii), four opossums and one sheep (R. rickettsii). The ticks Amblyomma ovale, Amblyomma dubitatum, Amblyomma sculptum, Dermacentor nitens and Rhipicephalus microplus, and the fleas Ctenocephalides felis and Siphonaptera: Rhopalopsyllidae cf. Rhopalopsyllus were collected from the sampled hosts. Results showed that horses and opossums may be used as sentinels for BSF in the \"Luiz de Queiroz\" Campus, but the sheep do not. It wasn\'t possible to determine if the cows may be used as sentinels. R. bellii, or a very closely related microorganism, occurs in the urban area of the \"Luiz de Queiroz\" Campus and is capable to infect horses. R. rickettsii, or a very closely related microorganism, occurs in capybara-transit areas of the \"Luiz de Queiroz\" Campus

A Febre Amarela (FA) é uma doença viral infecciosa, não contagiosa que pode se manifestar desde um quadro febril até a forma clássica íctero-hemorrágica, cujo agente etiológico é o vírus da febre amarela (VFA). A doença tem avançando para as regiões Sudeste e Sul com um aumento de 4 vezes no número de vítimas fatais. O presente trabalho teve como objetivos avaliar a possível circulação do vírus da febre amarela silvestre, através da detecção de anticorpos IgM por meio da técnica de MAC-ELISA, e anticorpos IgG, pelas técnicas de Inibição da hemaglutinação e Neutralização; detecção do genoma viral utilizando a técnica de RT-PCR no soro de indivíduos assintomáticos; bem como avaliar a proteção vacinal, por meio da técnica de neutralização em soros de indivíduos das zonas rurais do município de Jacupiranga e Teodoro Sampaio. Um total de 238 soros foram coletados, 152 (Jacupiranga) e 86 (Teodoro Sampaio). Foram detectados um total 15,9% (38/238) de anticorpos IH contra o vírus selvagem e/ou vacinal. Destes 13,16% (5/38) anticorpos IH foram provenientes dos soros de Jacupiranga e 86,84 (33/38) de Teodoro Sampaio. Anticorpos neutralizantes foram detectados em 34% (13N/38IH) dos IH reativos, destes 15,38% (2/13) foram oriundos deJacupiranga e 84,62% (11/13). A detecçção de anticorpos neutralizantes nos indivíduos de Jacupiranga levantam a necessidade de pesquisas futuras na busca do vírus da febre amarela nos seus reservatórios selvagens e vetores. Não houve a detecção do genoma viral por RTPCR nas duas populações, bem como a detecção de anticorpos IgM específicos, por meio das reações de MACELISA, o que evidencia a não circulação recente deste vírus na população estudada. O grau de imunizaçao na população de Teodoro Sampaio, com histórico de vacinação, por meio das reações de IH e Neutralização foi baixo, uma vez que somente 42,30% da população apresentou anticorpos inibidores da hemaglutinação e o grau de proteção pela reação de neutralização foi de apenas 33,33%. Este trabalho aponta não só para a necessidade de monitoramento pós-vacinal em áreas endêmicas de febre amarela, com indicação de vacinação, como também a necessidade de estudos epidemiológicos, uma vez que se detectou reação monotípica no teste do IH, além de anticorpos neutralizantes para o vírus selvagem da febre amarela em um indivíduo residente em município de risco para a febre amarela. / Yellow fever (YF) is an non-contagious infection disease. The clinical signs can be a nonspecific fever or the classical ictero-hemorrhagic form as a result of the Yellow Fever virus (YFV) infection. Considering the recent spread of the disease to the South and Southeast of Brazilian regions and the increased number of fatal cases, the aim of this study was to evaluate the possible circulation of the YFV, using the IgM enzyme-linked immnunosorbent assay (MACELISA) and Reverse transcriptase polymerase chain reaction (RT-PCR), as well as, to conduct a serological inquire and evaluate the protective vaccine response, by the hemagglutination inhibition test (HI) and serum neutralization test (SN), in the rural population of Jacupiranga and Teodoro Sampaio, located in the southern region of Brazil. A total of 238 serum samples were tested, 152 from Jacupirang and 86 from Teodoro Sampaio. Of the serum collected, 15,9% (38/238) were positive by HI, using wild and vaccine strains of YF, and out of these 13,16% (5/38) were from Jacupiranga and 86,84% (33/38) were from Teodoro Sampaio. Neutralizing antibodies were detected in 34% of the HI positive samples (13SN/38HI) and out of these 15,38% (2/13) were from Jacupiranga and 84,62% (11/13) were from Teodoro Sampaio. None of the samples were positive by MACELISA and RT-PCR indicating no evidences of recent virus circulation in the population analyzed in this study. However, the YF neutralizing antibodies detection in samples from Jacupiranga indicates the necessity of further researches in order to detect the YFV in its wild reservoirs and vectors. On the other hand, considering that 42,30% of the Teodoro Sampaio samples were positive by HI and out of these only 33,33% had neutralizing antibodies to the YFV, our results also pointed out to the importance of pos-vaccination protective immunity surveys, in order to evaluate the efficiency of the vaccines in endemic areas.

O dengue e o dengue hemorrágico são considerados como as arboviroses mais importantes do ponto de vista da saúde pública além de serem também as mais disseminadas. O greening ou huanglongbing (HLB), por sua vez, é uma doença de difícil controle e rápida disseminação que afeta seriamente a produção de citros no mundo todo. É considerada a pior doença de citros da atualidade pois não tem cura e leva ao declínio e morte das árvores em alguns anos. O DMDS é um composto sulfúrico volátil derivado de plantas e que tem despertado um crescente interesse devido a sua comprovada atividade repelente e inseticida além de ação nematicida e disinfectante do solo. Visando oferecer uma alternativa para o controle de ambas as doenças, este trabalho teve como objetivo desenvolver um método de microencapsulação por spray drying e spray congealing para o dimetil dissulfeto (DMDS), visando a redução da sua volatilidade através de uma liberação controlada para o ambiente. Dessa forma, tornar-se-ia viável sua utilização como repelente, larvicida e inseticida no combate ao vetor do dengue além da sua utilização como repelente no controle do greening nas lavouras de citrus. Tentou-se a microencapsulação através de spray congealing utilizando enxofre como microencapsulante mas não se obteve sucesso devido as características térmicas do enxofre. Foram obtidas micropartículas de DMDS microencapsulado em goma arábica através da técnica de spray drying. As micropartículas e o processo de secagem foram caracterizados com relação ao rendimento de secagem, rendimento de microencapsulação, morfologia, teor de água residual, atividade de água, densidades aparente e compactada e propriedades de fluxo. Confirmou-se a possibilidade de microencapsulação de DMDS por spray drying e eficiência da goma arábica na retenção do mesmo. As partículas obtidas apresentaram boas propriedades de atividade de água, teor de água residual e densidade mas propriedades de fluxo que requerem melhoria. Foi feito também um estudo simplificado da viabilidade técnico-econômica da implantação de uma unidade de produção de DMDS microencapsulado. Esse estudo foi baseado no processo de microencapsulação estudado. Foram analisados diversos parâmetros econômicos e através destas análises verificou-se que a produção de DMDS microencapsulado pelo método utilizado seria economicamente viável. / Dengue fever and dengue hemorrhagic fever are not only considered the most important arboviruses from public health standpoint but also the most disseminated ones. Greening or huanglongbing (HLB) is a citrus disease of difficult control and fast dissemination that affects citrus production all over the world. It is considered the worst citrus disease nowadays since it does not have a cure and it causes the decline and death of the trees in a few years. Dimethyl disulfide is a volatile sulphur compound derived from plants and that has aroused growing interest due to its proved repellence and insecticidal activity, soil disinfection and nematocidal properties. Therefore, this work aimed at developing a DMDS microencapsulation method via spray drying and spray congealing in order to decrease DMDS\' volatility through a controlled release to the environment and offer a control alternative to both diseases. This would make DMDS use as a repellent, larvicide and insecticide of dengue fever\'s vector and also its use in greening control as a repellent viable. We tried to microencapsulate the DMDS through spray congealing using sulfur as a microenpsulating agent but it was unsuccessful due to the thermal characteristics of sulfur. DMDS was microencapsulated in Arabic gum through spray drying. Drying yield, microencapsulation yield, morphology of the particles, residual water percentage, water activity, bulk and tapped density and flow properties were used to characterize the microparticles and the drying process. Feasibility of DMDS microencapsulation and Arabic gum efficiency in DMDS retention were confirmed. The microparticles presented good bulk and tapped density, residual water percentage and water activity properties though its flow properties requiring further improvement. A simplified technical-economical evaluation of a DMDS microencapsulation factory was also done. This evaluation was based on the studied microencapsulation process. Many economical parameters were analysed and those analyses showed that DMDS microparticles production using the studied method would be economically viable.

Em janeiro de 2005, foram coletados 31 carrapatos adultos da espécie Amblyomma triste em uma propriedade rural da CESP, localizada no município de Paulicéia, Estado de São Paulo. Três carrapatos foram positivos para o teste de hemolinfa, demonstrando estruturas compatíveis com riquétsias no interior de hemócitos. Dois desses carrapatos foram submetidos à tentativa de isolamento de riquétsias em células Vero, através da técnica de Shell vial. Um isolado foi obtido com sucesso, estando já estabelecido em cultivo celular, com várias passagens e partidas congeladas. Do restante do carrapato utilizado para este isolamento, foi extraído o DNA e este foi submetido a PCR para um fragmento do gene ompA de Rickettsia spp. Foi realizada a caracterização molecular do isolado, através do sequenciamento genético de quatro genes de Rickettsia spp: gltA, htrA, ompA e ompB e os genes apresentaram 99,8 a 100% de identidade com as seqüências correspondentes de Rickettsia parkeri no GenBank. Todos os 31 carrapatos tiveram o DNA extraído, sendo processados pela PCR para um fragmento do gene gltA e para um fragmento do gene ompA. Três (9,7%) foram positivos a PCR para o gene gltA e os mesmos 3 carrapatos foram positivos para o ompA, sendo exatamente os 3 carrapatos previamente positivos ao teste de hemolinfa). O material amplificado destes 3 carrapatos para o fragmento de gene ompA foi processado para o sequenciamento automático de nucleotídeos resultando em 100% de identidade com a seqüência correspondente de Rickettsia parkeri no GenBank. Este trabalho relata pela primeira vez a bactéria R. parkeri no Brasil, o que foi confirmado pelo isolamento do agente em cultivo de células / In January 2005, 31 adult free-living ticks of the species Amblyomma triste were collected in the CESP rural farm located in the city of Paulicéia, state of São Paulo, Brazil. In the laboratory, 3 of these ticks were positive by the hemolymph test, showing structures compatible with Rickettsia within the hemocytes. Attempts to isolate Rickettsia were performed in two hemolymph-positive ticks by the Shell-vial technique. One isolate was successful obtained, being established in Vero cell culture, with several passages performed. DNA extracted from infected cells was submitted to PCR targeting fragments of four Rickettsia genes: gltA, htrA, ompA and ompB. DNA sequences obtained from PCR products of these four genes showed 99.8 to 100% of similarity with corresponding sequences of Rickettsia parkeri in the Genbank. DNA was extracted from all 31 ticks and processed by PCR targeting a fragment of the rickettsial gltA gene and a fragment of ompA gene. Three (9.7%) ticks were positive for both genes, being the same ticks previously positive by the hemolymph test. PCR products of these ticks were sequenced, being 100% identical to the corresponding sequence of Rickettsia parkeri in GenBanK. This study perfoms the first report of R. parkeri in Brazil, confirmed by the isolation of the agent in cell culture

A presente análise das três séries históricas, compondo um total de 42 casos de hepatopatias fulminantes da região Amazônica, teve por objetivos o estudo de aspectos morfológicos e imuno-histoquímicos no diagnóstico diferencial entre febre amarela (FA), hepatite de Lábrea (HL) e de outras entidades. Visou, ainda, aprimorar o conhecimento de aspectos da morfogênese da morte hepatocelular, de eventual fibrose, relacionando-as aos padrões de regeneração e de lesões vasculares, conforme recentemente descrito na gênese de hepatopatias crônicas. Dentre o extenso painel de critérios histológicos aqui estudados, os padrões de morte hepatocelular e sua distribuição, incluindo corpos apoptóticos medio-zonais, assim como a balonização foram os achados mais característicos da FA, enquanto as células em mórula foram o principal achado na HL. Dezenove casos bem caracterizados (10 FA e 9 HL) foram então submetidos a estudos imuno-histoquímicos para a detecção dos antígenos da FA, AgHBs e antígeno do vírus da hepatite D (VHD), sendo então demonstrado que, em ambas as doenças, mas principalmente na HL, flebite, principalmente de ramos da veia porta, foi evidente e deve ter tido participação na patogênese do dano hepático, com extensa extinção parenquimatosa hepática e aproximação de espaços porta. O padrão de regeneração também foi marcante: nos casos de FA, um elevado índice de proliferação celular foi observado enquanto que, na HL, multinucleações e transformação pseudoacinar, associadas a depósitos portais de colágeno do tipo I e de fibras elásticas, foram encontrados. Concluindo, a pesquisa imuno-histoquímica de antígenos virais permitiu a caracterização etiológica dos casos destas importantes séries históricas de hepatopatias fulminantes da Amazônia, mesmo em amostras arquivadas em parafina por até sete décadas. Permitiu, ainda, o relato original de cinco casos de possível superposição de infecção pelos vírus da FA, VHB e/ou VHD. Dentre os aspectos histopatológicos, o quadro dominante na FA fulminante incluiu apoptose medio-zonal associada com flebite portal e um alto índice de proliferação celular, em pacientes sem evidência de dano hepático prévio. Por outro lado, a HL fulminante mostrou extensa necrose lítica de hepatócitos, associada à flebite portal e de veia hepática e à presença de células em mórula, em pacientes com evidências morfológicas de doença hepática crônica. / This study aimed at assessing morphological and immunohistochemical aspects useful for the differential diagnosis of yellow fever (YF), Labrea hepatitis (LH) and other entities by revisiting 42 fulminant hepatic failure cases, from three historical series from Amazon Basin. Additional studies were performed aiming at further understanding the morphogenesis of hepatocelular death, in relation to regeneration and fibrosis patterns and to vascular lesions, as recently described in chronic hepatic diseases. Among the extensive panel of histological criteria studied, liver cell death pattern and distribution, including midzonal apoptotic bodies, as well as hepatocelular ballooning degeneration were YF most characteristic findings, while morula cells were the major hint for LH. Five cases were herein suggested as coinfected with YF, HBV and/or HDV, a finding not previously reported. Nineteen well characterized cases (10 YF and 9 LH) were further submitted to immunohistochemical studies for YF antigen, HBsAg and Delta virus Ag. In both diseases, but mainly in LH, phlebitis, mainly of portal vein branches, was evident and closely related to the degree of hepatocellular damage, with severe hepatic parenchymal extinction and portal tract approximation. Regeneration pattern was also remarkable: in YF cases, a high hepatocellular proliferative index was detected whereas in LH, multinucleation and pseudo-acinar transformation, associated with portal type I collagen and elastic fiber deposition were found. In conclusion, immunohistochemical viral antigen detection yielded further etiological characterization of these important historical cases of fulminant hepatic failure from Amazon Basin, even in paraffin samples stored for up to seven decades. YF morphology depicted midzonal apoptosis, portal phlebitis and a high hepatocellular proliferative index, in patients without evidence of previous hepatic injury. On the other hand, fulminant LH showed extensive lytic hepatocellular necrosis, portal and hepatic vein phlebitis and the presence morula cells, in patients with morphological evidences of chronic liver disease.

La Fièvre de la Vallée du Rift (VFVR) est une arbovirose zoonotique affectant principalement les ruminants et les humains. Son éco-épidémiologie complexe implique de nombreuses espèces de vecteurs, d'hôtes et de voies de transmission. Ainsi, différents mécanismes de transmission et d'émergence sont impliqués dans la circulation du virus de la FVR (VFVR) et ceux-ci dans des écosystèmes contrastés d'Afrique, de la Péninsule Arabique et des îles du sud-ouest de l'Océan Indien, dont l'île de Madagascar.Par sa superficie, sa grande diversité éco-climatique et sa faune et flore endémique, Madagascar est considérée comme une île continent. On y retrouve, en effet, des écosystèmes variés plus ou moins favorables aux moustiques : semi-arides dans le sud-ouest, humides et froids sur les hautes terres centrales, per-humide dans l'est et humides et chaud dans le nord-ouest. Madagascar a été affectée par deux épidémies de FVR en 1990-91 puis 2008-09. Une étude menée lors de la dernière épidémie a montré que le virus avait largement diffusé dans l'île de façon hétérogène.Compte tenu de la complexité des mécanismes de transmission de la FVR et de la diversité des écosystèmes de Madagascar, nous avons supposé que cette hétérogénéité spatiale était due à des mécanismes de transmission et d'émergence qui variaient en fonction des écosystèmes de l'île. Ainsi, le premier objectif de ce travail de thèse étaient de déterminer les mécanismes et les dynamiques de transmission de la FVR inhérents aux différents écosystèmes de Madagascar. Le second objectif a été d'identifier les mécanismes d'émergence de la FVR à Madagascar et de déterminer s'il sera possible, et nécessaire, de prédire cette émergence à l'échelle des écosystèmes.Dans le cadre de ce travail de thèse deux enquêtes sérologiques nationales, l'une bovine (2008) et l'autre humaine (2011-13) ont, premièrement, été analysées par un modèle linéaire mixte généralisé afin d'identifier les facteurs environnementaux et comportementaux favorables à la circulation du virus chez les bovins et les humains. Deuxièmement, deux enquêtes sérologiques bovines, l'une réalisée en 2008 et l'autre en 2014, ont été analysées pour reconstruire la dynamique de transmission de la FVR dans les différents écosystèmes de l'île. Cette reconstruction a été réalisée à partir de données de séroprévalence et d'âge inclues dans un modèle Bayésien hiérarchique pour estimer la force d'infection annuelle de 1992 à 2014. Enfin, afin de faire le lien biologique avec les résultats des travaux menés à une échelle nationale et de décrire les mécanismes de transmission à une échelle fine, des enquêtes longitudinales entomologiques et sérologiques ont été réalisées entre 2015 et 2016 dans un écosystème à risque. Et ceci, afin de décrire la transmission saisonnière du VFVR chez les ruminants associée à la dynamique de transmission des vecteurs potentiels.Nos résultats ont montré que la région du nord-ouest de l'île est une région à risque de transmission. D'une part, elle est constituée d'environnements associant une forte densité de bovins à des zones humides, inondables et irriguées, favorables aux espèces d'Anopheles et Culex. D'autre part, le VFVR semble avoir circulé de façon relativement intense lors de la période inter-épizootique de 1992 à 2007, puis sa transmission a soudainement augmenté en 2007-2008, ce qui est concomitant avec l'apparition des foyers de FVR en 2008. Pour finir, 6 ans après l'épidémie de FVR à Madagascar, le virus semble toujours circuler à bas bruit dans la région. Cette circulation étant probablement due à une transmission vectorielle favorisée par l'abondance de vecteurs potentiels dans la région.Les résultats de ces différents travaux nous ont permis de présenter des hypothèses de transmission dans les différents écosystèmes de l'île et ainsi de proposer des stratégies de surveillance, de prévention et de lutte contre la FVR adaptées au contexte de Madagascar. / Rift Valley fever (RVF) is a zoonotic vector-borne disease affecting ruminants and humans. Its complex eco-epidemiology involves several species of vectors, hosts and transmission routes. These particularities allowed the circulation of RVF virus (RVFV) in a variety of ecosystems involving different transmission and emergence mechanisms. Indeed, the RVFV has affected contrasted eco-regions in Africa, Arabian Peninsula and South-West Indian Ocean islands, including Madagascar.Madagascar is considered as a continent island due to its ecological diversity and its endemicity level of the flora and the fauna. In particular, the variation of the Malagasy ecosystems (semi-arid in the south, humid and cold in the highlands, humid and warm in the north-west and per-humid in the east) has an impact in their presence and /or the relative abundance of some mosquito species. Madagascar was heavily affected by RVF in 1990-91 and 2008-2009, with evidence of a large and heterogeneous spread of the disease.Thus considering the diversity of RVF eco-epidemiological cycles and the variety of Malagasy ecosystems, we hypothesized that, in Madagascar, the mechanisms of transmission would be different according to these ecosystems. Therefore, the first objective of this thesis was to understand the mechanisms and the dynamics of transmission of RVFV in the different ecosystems. The second objective was to determine the mechanisms of emergence of RVFV and if it would be necessary and possible to predict the emergence of RVFV outbreaks according to the ecosystems.Firstly, we analyzed both cattle and human serological data performed at the national level using generalized linear mixed models to identify the environmental and behavioral factors associated with RVF transmission in both cattle and human. Secondly, we reconstructed the dynamic of transmission of RVF in the different Malagasy ecosystems. Seroprevalence data of cattle of known age were fitted using Bayesian hierarchical models to estimate the annual force of infection from 1992 to 2014. Thirdly, to understand the biological process link to the mechanisms of transmission at the national scale, we investigated the fine scale mechanisms of transmission of RVFV in pilot area of an at-risk region. We, thus, performed both longitudinal entomological and serological surveys between 2015 and 2016, in order to describe the seasonal transmission of RVFV among ruminants and its association with the dynamics of RVFV potential vectors.Our results showed that the northwestern part of Madagascar is an at-risk region for RVFV transmission. On one hand, it is characterized by high cattle densities associated with humid, floodplain and irrigated areas suitable for RVFV potential vector like Anopheles and Culex species. On the other hand, RVFV had probably circulated intensively in the region during the 1992-2007 inter-epizootic period and its transmission increased suddenly in 2007-08, almost concomitantly with the first outbreaks recorded in 2008. Finally, RVFV was still circulated in the northwestern region at low level, 6 years after the last epidemic. This circulation is likely due to vectorial transmission favoring by the abundance of several potential vectors of RVFV in this pilot region.Finally, our better understanding of the mechanisms of transmission of RVFV throughout Madagascar allowed us to propose hypothesis of transmission in different ecosystems of Madagascar and consequently refine strategies for RVF surveillance and prevention.