Shiga toxin-producing E. coli (STEC) have important public health and food safety implications. Cattle are the primary reservoir for STEC, which are transmitted to humans via contact with cattle or related food products. Dairy farms in particular have been incriminated as an important source of STEC. The broad aim of this study was to examine in depth the epidemiology of STEC on the dairy farm. The presence of STEC on three Australian dairy farms was surveyed. This aimed to provide data on the prevalence and nature of STEC on Australian dairy farms, as well as to examine in more detail the pre-harvest/slaughter ecology of STEC. STEC, E. coli O157:H7 and E. coli O26:H11 prevalences were similar to those from dairy farms in other countries. Replacement heifers were the most important source of STEC on the farms. Calves excreted STEC from an early age, with faecal prevalence peaking at weaning. Higher STEC prevalence was also associated with group housing of calves during weaning. Calf isolates were potential human pathogens based on serotype and virulence markers. Clonal relationships between isolates were analysed. Calf isolates were diverse and had a high clonal turnover. STEC isolated from within the same farm had a higher genetic similarity than those from different farms. Vertical and horizontal transmission were both identified among cattle. The farm environment was also identified as an important source of STEC. Reasons for increased levels of STEC excretion by calves were investigated. Two broad hypotheses for higher faecal shedding were proposed and examined individually. The first was that an animal is more likely to excrete STEC when its exposure to STEC is greater, thus promoting inoculation of the gastrointestinal tract. Calves were experimentally inoculated with a traceable STEC strain to examine the infection dynamics of STEC within cattle groups, and explore the effect of calf management procedures. Calves which were housed in groups and co-jointly fed and managed had a higher prevalence of the inoculation strain than animals housed individually. The test strain was readily isolated from the hides and saliva of inoculated calves, as well as their immediate environments. Calves become infected with STEC via the faecal-oral route, iv either by direct contact with other calves, or indirectly through contact with faecally contaminated materials. The second hypothesis was that individual animals are variably susceptible to intestinal colonisation by STEC, which leads to differing magnitudes and durations of STEC carriage. Factors influencing colonisation susceptibility to STEC and the mechanisms behind these factors were also examined. In order to compare enteric colonisation under a range of different conditions, a suitable experimental system was developed. In vitro organ culture of explanted ruminant colonic tissues provided a laboratory model that was representative of in vivo bacterial-mucosal attachment. The degree of STEC colonisation was enumerated using an immunofluorescent filtration technique. The quantitative colonisation assay was applied to determine the effects of host-dependant variables on STEC colonisation. Colonic tissues from weaning calves and adult cattle did not differ significantly in their susceptibility to colonisation; nor did tissues from cattle fed either high forage or high grain diets. Colonic explants from sheep, however, demonstrated significantly higher numbers of adherent STEC than bovine explants. It was therefore concluded that while species-specific differences in host tissues may mediate STEC carriage differences, this did not explain in vivo variability in age and diet related excretion. Factors that indirectly affect the susceptibility of host tissues to colonisation were examined. E. coli O157:H7 cultured in media designed to represent the enteric contents of a well-fed ruminant colonised the colonic mucosa in reduced numbers, indicating that age and diet may be correlated with differences in STEC carriage and excretion because of differing physiological augmentation of the intra-enteric environment. In conclusion, while group dynamics and management practices may increase STEC shedding prevalences for cattle via increased STEC exposure, factors that modulate an individual ruminant’s gastrointestinal carriage of STEC have a significant role in mediating STEC excretion. Either directly or indirectly, species, age and diet can affect the numbers of STEC that colonise the bowel wall, thereby influencing the magnitude and duration of STEC excretion. Both of these features of ruminant STEC ecology should be addressed in order to reduce the pre-slaughter/harvest presence of STEC.

Orientador: Marcelo Vasconcelos Meireles / Resumo: Cryptosporidium spp. são parasitos protozoários que infectam principalmente as células epiteliais do trato digestivo em vários animais, incluindo humanos. Este protozoário causa doença entérica, que se caracteriza como diarréia auto-limitante em indivíduos saudáveis, ou mesmo doença fatal em pacientes imunodeficientes. Cryptosporidium parvum é a principal causa de infecção em mamíferos e é o principal responsável pela criptosporidiose zoonótica. Novos métodos de detecção, prevenção, tratamento e estratégias de controle para criptosporidiose em seres humanos são cada vez mais necessários. Anticorpos e proteínas recombinantes têm potencial para o desenvolvimento de medicamentos, vacinas ou podem ser usados para desenvolver técnicas de diagnóstico mais acessíveis com alta sensibilidade e especificidade. Neste estudo, o objetivo principal foi a expressão da proteína recombinante CP41 de C. parvum em Escherichia coli e produção de um anticorpo específico para CP41 recombinante (rCP41), visando a detecção de oocistos de Cryptosporidium por imunofluorescência. / Doutor

Medical cartography can provide valuable insights into the epidemiology and ecology of infectious diseases, providing a quantitative representation of the distribution of these pathogens. Such methods therefore provide a key step in informing public health policy decisions ranging from prioritising sites for further investigation to identifying targets for interventions. By increasing the resolution at which risk is defined, policymakers are provided with an increasingly informed approach for considering next steps as well as evaluating past progress. In spite of their benefits however, global maps of infectious disease are lacking in both quality and comprehensiveness. This thesis sets out to investigate the next steps for medical cartography and details the use of species distribution models in evaluating global distributions of a variety of zoonotic diseases of public health importance. Chapter 2 defines a methodology by which global targets for infectious disease mapping can be quantitatively assessed by comparing the global burden of each disease with the demand from national policymakers, non-governmental organisations and academic communities for global assessments of disease distribution. Chapter 3 introduces the use of boosted regression trees for mapping the distribution of a group of vector-borne diseases identified as being a high priority target, the leishmaniases. Chapter 4 adapts these approaches to consider Ebola virus disease. This technique shows that the West African outbreak was ecologically consistent with past infections and suggests a much wider area of risk than previously considered. Chapter 5 investigates Marburg virus disease and considers the variety of different factors relating to all aspects of the transmission cycle that must be considered in these analyses. Chapters 6 and 7 complete the mapping of the suite of viral haemorrhagic fevers by assessing the distribution of Crimean-Congo haemorrhagic fever and Lassa fever. Finally, Chapter 8 considers the risk that these viral haemorrhagic fevers present to the wider African continent, quantifying potential risk of spillover infections, local outbreaks and more widespread infection. This thesis addresses important information gaps in global knowledge of a number of pathogens of public health importance. In doing so, this work provides a template for considering the global distribution of a number of other zoonotic diseases.

Memoria para optar al Título Profesional de Médico Veterinario / La interfaz entre humanos, animales domésticos, silvestres y su entorno, sumado a procesos de desertificación, urbanización y cambio climático han derivado en cambios en la dinámica de las enfermedades y al mismo tiempo, han obligado a estudiar las enfermedades transmitidas entre humanos y animales (zoonosis), bajo el enfoque global definido como “Una Salud”. Esto ha planteado la necesidad de direccionar el concepto de salud y considerar la salud de humanos, animales domésticos, silvestres y del ambiente, como parte de las políticas de salud pública en el mundo entero. En Chile, la salud de humanos y animales es manejada por diferentes ministerios, por lo que la prevención y control de zoonosis toman caminos distintos. El objetivo de este estudio fue evaluar las actividades de prevención, vigilancia y control de las zoonosis prioritarias en Chile, bajo el enfoque “Una Salud”. Las enfermedades prioritarias se definieron de acuerdo a su prevalencia, notificación obligatoria y riesgo potencial de introducción al país. Se compararon las recomendaciones de la Organización Mundial de la Salud (OMS) y de la Organización Mundial de Sanidad Animal (OIE) con las actividades realizadas a nivel local por el Ministerio de Salud (MINSAL) y el Servicio Agrícola y Ganadero (SAG). Además, a nivel nacional, se analizó el enfoque “Una Salud” mediante Análisis de Coordenadas Principales. Los resultados muestran diferencias en los esfuerzos dirigidos a las zoonosis de acuerdo a la población que se encuentra en riesgo y demuestran que, en la mayoría de los casos, las actividades de prevención, vigilancia y control de enfermedades no consideran a la fauna silvestre. Se concluye que en Chile los lineamientos de “Una salud” no han sido del todo implementados en el manejo de las enfermedades zoonóticas prioritarias.

Resumo: A leishmaniose visceral (LV) é uma enfermidade infecciosa de caráter zoonótico, endêmica em algumas áreas do Brasil, causada pela L. chagasi. A maior dificuldade encontrada para controlar a doença está relacionada ao seu diagnóstico, que apresenta limitações quanto aos seus resultados. Desta maneira, o estudo comparou duas provas sorológicas, a reação de imunofluorescência indireta (RIFI) e o ensaio imunoenzimático (ELISA); o exame parasitológico direto bem como a reação em cadeia pela polimerase (PCR), ambos de aspirado de linfonodo. Foram utilizados os iniciadores gênero-específicos LINR4 e LIN19 e os iniciadores RV1 e RV2 espécie-específicos para identificar a L. chagasi. Foram coletadas amostras de 100 cães sorologicamente positivos, provenientes do Centro de Controle de Zoonoses (CCZ) de Bauru, região endêmica, e de 100 cães provenientes do CCZ de Botucatu-SP, área não-endêmica para a enfermidade. A RIFI, o parasitológico e a PCR apresentaram especificidade de 100% e o ELISA de 99%. As sensibilidades foram 97,77%; 93,33% e 91,11%, para RIFI, ELISA e PCR respectivamente. A proporção de concordância entre as provas foi satisfatória, apresentando valores de P sempre menores que 0,05. Pode-se concluir que além do exame sorológico, pode-se utilizar também a PCR de linfonodo no diagnóstico da LVC, pois a associação de técnicas melhorou a detecção de cães infectados, contribuindo para o melhor controle desta zoonose. / Abstract: The visceral leishmaniasis (VL) is a zoonotic infectious disease, endemic in some areas from Brazil, caused by L. chagasi. The greatest difficulty to control the disease is related to its diagnosis, which present limitations related with the results. Thus, the study compared two serologic methods, the indirect fluorescent antibody test (IFAT) and the enzyme-linked immunosorbent assay (ELISA); the parasitological direct examination and the polymerase chain reaction (PCR), both drawn from the lymph node. The initiators used were gender-specific LINR4 and LIN19 and the initiators species-specific RV1 and RV2 to identify L. chagasi. The samples were collected from 100 dogs serologically positive, from the Center for Zoonoses Control (CZC) of Bauru, endemic region, and 100 dogs from the CZC of Botucatu-SP, an area considered non-endemic to the disease. The IFAT, the parasitological and the PCR showed 100% of specificity and ELISA 99%. The sensitivities were 97.77%, 93.33% and 91.11% for IFAT, ELISA and PCR respectively. The proportion of agreement between the methods was satisfactory, showing values of P always smaller than 0,05. It was concluded that in addition to the serologic methods, PCR of lymph node can also be used for CVL diagnosis, and that the combination of techniques improved the detection of infected dogs, contributing for better control of this zoonosis. / Orientador: Helio Langoni / Coorientador: Simone Baldini Lucheis / Banca: Antonio Carlos Paes / Banca: Paulo Eduardo Martins Ribolla. / Mestre

Made available in DSpace on 2014-06-11T19:30:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-06-26Bitstream added on 2014-06-13T19:18:35Z : No. of bitstreams: 1 camargo_jb_me_botfmvz.pdf: 604246 bytes, checksum: 07ea679245c94fa23e7b1461f7a2ce2a (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A leishmaniose visceral (LV) é uma enfermidade infecciosa de caráter zoonótico, endêmica em algumas áreas do Brasil, causada pela L. chagasi. A maior dificuldade encontrada para controlar a doença está relacionada ao seu diagnóstico, que apresenta limitações quanto aos seus resultados. Desta maneira, o estudo comparou duas provas sorológicas, a reação de imunofluorescência indireta (RIFI) e o ensaio imunoenzimático (ELISA); o exame parasitológico direto bem como a reação em cadeia pela polimerase (PCR), ambos de aspirado de linfonodo. Foram utilizados os iniciadores gênero-específicos LINR4 e LIN19 e os iniciadores RV1 e RV2 espécie-específicos para identificar a L. chagasi. Foram coletadas amostras de 100 cães sorologicamente positivos, provenientes do Centro de Controle de Zoonoses (CCZ) de Bauru, região endêmica, e de 100 cães provenientes do CCZ de Botucatu-SP, área não-endêmica para a enfermidade. A RIFI, o parasitológico e a PCR apresentaram especificidade de 100% e o ELISA de 99%. As sensibilidades foram 97,77%; 93,33% e 91,11%, para RIFI, ELISA e PCR respectivamente. A proporção de concordância entre as provas foi satisfatória, apresentando valores de P sempre menores que 0,05. Pode-se concluir que além do exame sorológico, pode-se utilizar também a PCR de linfonodo no diagnóstico da LVC, pois a associação de técnicas melhorou a detecção de cães infectados, contribuindo para o melhor controle desta zoonose. / The visceral leishmaniasis (VL) is a zoonotic infectious disease, endemic in some areas from Brazil, caused by L. chagasi. The greatest difficulty to control the disease is related to its diagnosis, which present limitations related with the results. Thus, the study compared two serologic methods, the indirect fluorescent antibody test (IFAT) and the enzyme-linked immunosorbent assay (ELISA); the parasitological direct examination and the polymerase chain reaction (PCR), both drawn from the lymph node. The initiators used were gender-specific LINR4 and LIN19 and the initiators species-specific RV1 and RV2 to identify L. chagasi. The samples were collected from 100 dogs serologically positive, from the Center for Zoonoses Control (CZC) of Bauru, endemic region, and 100 dogs from the CZC of Botucatu-SP, an area considered non-endemic to the disease. The IFAT, the parasitological and the PCR showed 100% of specificity and ELISA 99%. The sensitivities were 97.77%, 93.33% and 91.11% for IFAT, ELISA and PCR respectively. The proportion of agreement between the methods was satisfactory, showing values of P always smaller than 0,05. It was concluded that in addition to the serologic methods, PCR of lymph node can also be used for CVL diagnosis, and that the combination of techniques improved the detection of infected dogs, contributing for better control of this zoonosis.

Foi efetuado um inquérito epidemiológico do potencial zoonótico da população canina da Estância Turística de Ibiúna, SP. As zoonoses investigadas foram: leishmaniose, leptospirose, brucelose (B.canis), toxoplasmose, neosporose e doença de Chagas. As características analisadas foram: ocorrência, prevalência, distribuição espacial e fatores de risco. As colheitas de sangue foram efetuadas no período de 2007 a 2008 de uma amostra representativa (n=570), aleatória e estratificada da população canina do município. Por ocasião das colheitas de sangue os proprietários dos animais responderam a um questionário elaborado para permitir o cálculo dos fatores de risco. Os 48 bairros do município foram agrupados em quatro regiões caracterizadas por: região 1 composta por áreas mistas de urbanização recente, sem infra-estrutura adequada e com deficiência de serviços e áreas rurais formadas por pequenas propriedades agrícolas; região 2 de característica predominantemente rural formada por pequenas propriedades agrícolas e sítios circundados por áreas de mata; região 3 formada por área urbanizada que dispõe infra-estrutura organizada; região 4 também apresenta o predomínio de pequenas propriedades rurais para plantio e lazer, circundadas por áreas de mata. Não foram examinados animais do Parque Estadual de Jurupará. A leptospirose foi investigada pela técnica de soroaglutinação microscópica, com uma coleção de 24 sorovariedades de leptospiras, a leishmaniose por uma reação imunoenzimática, a brucelose (B.canis) por cultivo microbiológico e toxoplasmose, neosporose e doença de Chagas por imunofluorescência indireta. Os resultados obtidos foram analisados pelo teste de qui quadrado ou exato de Fisher, quando indicado, o nível de significância adotado foi o de 0,05. Foram encontrados animais reatores para as seis zoonoses estudadas, com taxas de prevalência de: 1,1%, 2,3%, 6,1%, 7,0%, 32,8% e 55,1%, respectivamente para: brucelose por (B.canis), leishmaniose, doença de Chagas, neosporose, leptospirose e toxoplasmose. As variantes sorológicas de leptospiras predominantes em ordem decrescente de ocorrência foram: Pyrogenes, Autumnalis e Canicola. As variáveis sexo masculino, idade adulta, presença de roedores, permanência nas vias públicas, ingestão de carne crua e atividade sexual foram caracterizadas como fatores de risco para leptospirose e toxoplasmose; a permanência nas vias públicas foi caracterizada como fator de risco para brucelose; sexo masculino, idade adulta e atividade sexual foram caracterizados como fatores de risco para neosporose; contato com carrapatos foi caracterizado como fator de risco para doença de Chagas. As prevalências de leishmaniose, leptospirose, brucelose, toxoplasmose e neosporose não diferiram segundo área rural ou urbana bem como nas quatro regiões em que o município foi dividido. A prevalência da doença de Chagas foi idêntica em área rural ou urbana, mas o valor observado na região 4 (bairros: Campo Verde, Rio Una de Cima, Ressaca e Paruru) foi superior ao encontrado nas demais. / A seroepidemiologic survey was performed aiming to evaluate the zoonotic potential of the canine population of the tourist city of Ibiúna, São Paulo, Southeastern Brazil. The frequency of the occurrence, spatial distribution and associated risk factors of leishmaniasis, leptospirosis, brucellosis (Brucella canis), toxoplasmosis, neosporosis and Chagas' disease were investigated during the period of 2007 to 2008, in 570 blood samples gathered randomly from a stratified canine population, divided in 48 districts of the municipality which were grouped into four main regions characterized as: region 1 consists of mixed areas of recent urbanization without adequate infrastructure and services and rural areas formed by small properties; region 2 predominantly agricultural characteristic with small rural farms and properties surrounded by forest areas; region 3 formed by urbanized area with organized infrastructure, region 4 also presents the predominance of small country properties for planting and leisure, surrounded by forest areas. The animals of the State Park of Jurupará were not examined. During the blood collection, a questionnaire was applied to the owners of animals, in order to afford the epidemiological profile of the population and to carry out statistical analysis of risk factors. Leptospirosis was investigated by microscopic serum agglutination technique using a collection of 24 leptospira serovars, for leishmaniasis it was employed the ELISA technique and for brucellosis, by microbiological cultivation of B. canis and the toxoplasmosis, neosporosis and Chagas' disease, by using the indirect immunofluorescence techniques. The results were analyzed by the qui square (X2) test or by the Fisher's exact test, when indicated, using the significance level of α = 0.05. Positive reactant animals were found for leishmaniasis, leptospirosis, brucellosis, toxoplasmosis, neosporosis and Chagas' disease, with positive rates respectively of 2.3%, 32.8%, 1.05%, 55.1%, 7.0% and 6.1%. The most frequent serovars of leptospires, in decreasing order of occurrence were: Pyrogenes, Autumnalis and Canicola. Variables like "Male sex", "age", "presence of rodents", "permanence in streets", "ingestion of raw meat" and "sexual activity" were characterized as risk factors for the occurrence of leptospirosis and toxoplasmosis. Permanence in streets" was characterized as a risk factor for the occurrence of brucellosis. "Male sex", "age" and "sexual activity" were characterized as risk factors for the occurrence of neosporosis. The "contact with ticks" was characterized as a risk factor for the occurrence of Chagas' disease. The frequencies of occurrence of leishmaniasis, leptospirosis, brucellosis, toxoplasmosis and neosporosis were similar in rural and urban areas as well as in the four regions studied in Ibiúna. The positive rates of Chagas' disease was similar both in rural and urban areas, however, frequencies of Chagas' disease was significantly higher in region 4.

O ProMAC surgiu dentro da USP como resposta à demanda da comunidade, de abordar alguns problemas ambientais, inclusive a presença de cães errantes no campus. O presente trabalho teve como objetivo atender este programa no tocante à avaliação da dinâmica e da saúde da população de cães mantidos soltos na CUASO e dos cães recolhidos ao ATA. Utilizando a técnica de captura e recaptura fotográfica, a população de cães foi estimada em nove oportunidades ao longo de dois anos. No segundo ano, os cães dóceis foram individualmente identificados e, em quatro oportunidades, tiveram amostras biológicas coletadas (sangue, fezes e ectoparasitos). Os cães alojados no ATA foram identificados e as amostras coletadas em um único esforço contínuo ao longo de três meses. A estimativa da população errante variou entre 14 e 55 cães, com tendencia de queda não significativa ao longo do tempo. A população foi, em sua maioria composta de indivíduos machos (58,4%), adultos (77,8%) e dóceis (55,7%). A população errante apresentou alterações nos parâmetros hematológicos ao longo do ano, compatíveis com infecção subclínica, possivelmente causada por Hepatozoon canis, que teve aumento significativo de sua prevalência. Todos os cães foram negativos para Leishmania sp., Ricketsia sp., Erlichia sp. Não houve diferença significativa tanto para a SAM (Leptospira sp.,entre 14 e 50% - CUASO e 52,4% - ATA) quanto para a eliminação de ovos de Ancylostoma sp. nas fezes (entre 21 e 55% - CUASO e 27% - ATA) entre os cães da CUASO e do ATA, sendo o risco de infecção na comunidade universitária considerado baixo. A análise ambiental permitiu estabelecer que a fonte principal de alimento dos cães é a mesma dos humanos, fornecida próximo aos pontos de venda de alimentos, o que se torna preocupante ao sabermos que mais da metade destes cães são positivos para Toxoplasma sp. (entre 54 e 60%), sendo indicadores do risco ao ser humano. Os cães da população aversiva apresentam sinais reprodutivos (8,7% das fêmeas ao ano), mas os filhotes não foram encontrados possivelmente devido à baixa sobrevivência. Os adultos, tanto da população dócil como da população aversiva possuiam boa condição corporal, baixa mortalidade, sendo que os dóceis deixaram o campus mais frequentemente devido à adoção. O conjunto dos dados indicaram que o status sanitário dos cães alojados no abrigo foi semelhante àquela dos cães soltos, sendo que o bem-estar destes últimos foi maior, devido à condição precária em que o ATA era mantido, com a capacidade de alojamento de cães acima do limite máximo do abrigo. Como os cães da CUASO se distribuiam modulados pelo fornecimento de alimento e abrigo pelos usuários do campus, o manejo adequado destes cães deveria incluir o envolvimento da comunidade, além de sua responsabilização. A reprodução dos cães aversivos precisa ser eliminada, buscando métodos alternativos, devido à dificuldade de captura destes cães. O uso da área de mata destinada a pesquisa por estes cães representa um risco sanitário à comunidade universitária. / The ProMAC emerged within the University of São Paulo in response to a community demand, to address environmental problems, including the presence of stray dogs in its campus. This study aimed to address this program regarding the dynamics and health of the population of stray dogs in the campus and the dogs kept in the campus shelter. Using the technique of photographic mark and recapture, the dog population was estimated in nine occasions in a two years period. In the second year the docile dogs were individually identified and, on four occasions, had biological samples collected (blood, feces and ectoparasites). Dogs housed in the shelter were identified and biological samples were collected in a single effort over three months. The population estimates varied between 14 and 55 dogs, with a non-significant decrease trend over time. The population was mostly composed of males (58.4%), adults (77.8%) and docile individuals (55.7%). The stray population showed changes in hematological parameters throughout the year, consistent with subclinical infection, possibly caused by Hepatozoon canis, which had a significant increase in its prevalence. All dogs were negative for Leishmania sp., Rickettsia sp., Ehrlichia sp. There was no significant difference between either the MAT (Leptospira sp, between 14 and 50% -. campus and 52.4% - shelter) or the elimination of Ancylostoma sp. eggs in feces (between 21 and 55% - campus and 27% - shelter), between dogs from campus and shelter, and the risk of infection in the university community was considered low. Environmental analysis established that the stray dogs main food source are the human food given to them close to food selling points, which is a concern given that more than half of these dogs are positive for Toxoplasma sp. (from 54 to 60%) and would be risk indicators to humans. The aversive stray dogspopulation showed reproductive signs (8.7% of females per year), but the puppies were not found possibly due to low survival rate. Adults, both from docile and the aversive population, had good body condition, low mortality and the docile dogs left the campus more often due to adoption. The data indicated that the health of dogs housed in the shelter were similar to the stray population, and the welfare of the latter is higher due to the precarious condition that the shelter was maintained and the number of dogs kept being over the maximum capacity. As stray dogs were distributed and maintained by the food and shelter supplied by the campus users, the proper management of these dogs would include community involvement and responsibility. The reproduction of aversive dogs must be eliminated, seeking alternative methods, because of the difficulty of catching these dogs. Use of research forest area by these dogs poses a risk to the university community.

Memoria para optar al Título Profesional de Médico Veterinario. / Las zoonosis, o enfermedades infecciosas transmisibles entre los animales y el ser humano, constituyen un importante problema de salud pública a nivel global. En este contexto, se ha descrito una gran variedad de parásitos gastrointestinales de caninos que pueden representar un riesgo para la salud humana. La infección con estos agentes, en su mayoría, se produce a través del contacto de personas con elementos parasitarios de dispersión o resistencia en heces de perros, tales como, ooquistes, quistes o huevos. Las plazas públicas son un lugar común de reunión de personas con animales, principalmente perros, con y sin dueño, que presentan distintos estatus sanitarios y, por lo tanto, podrían constituir un área de riesgo para la transmisión de este tipo de parásitos a las personas. Con el fin de dilucidar la importancia de las plazas públicas como fuente de agentes parasitarios zoonóticos, se propuso detectar la presencia de ooquistes, quistes o huevos de parásitos con riesgo zoonótico en 170 muestras totales obtenidas de la principal plaza pública de cada una de las 34 comunas del Gran Santiago. Del total de muestras analizadas, 54 (31,7%) fueron positivas a algún parásito gastrointestinal con riesgo zoonótico. Estas muestras positivas provenían de 27 (79,4%) de las 34 plazas seleccionadas. De las muestras positivas analizadas, Toxocara canis fue el parásito más frecuentemente encontrado con 27 muestras positivas, luego Toxascaris leonina con 13 muestras, Taenia spp. con 10 muestras, Giardia spp con 6 muestras, anquilostomideos con 4 muestras, Criptosporidium spp. con 2 muestras y amebas con 1 muestra. Se concluye que un alto porcentaje de las plazas públicas poseen heces de perro con elementos parasitarios de dispersión o resistencia, tales como ooquistes, quistes y huevos de endoparásitos zoonóticos que pueden constituir un riesgo para la salud pública. / Zoonoses and communicable infectious diseases among animals and humans are a major public health problem globally. In this context, we have described a variety of canine gastrointestinal parasites, which may represent a hazard to human health. Infection with these agents mostly occurs through contact of people with elements of parasitic scatter or resistance in feces of dogs, such as oocysts, cysts or eggs. Public squares are a common meeting place for people with animals, mainly both dogs with or without owned, which have different health status, and therefore could be a risk area for transmission of these parasites to people. In order to elucidate the importance of public squares as a source of zoonotic parasitic agents, we proposed to detect the presence of oocysts, cysts or eggs of parasites with zoonotic risk in 170 total samples obtained from the main public square in each of the 34 communes in Gran Santiago. Of the total analyzed, 54 (31.7%) samples were positive for some gastrointestinal parasites with zoonotic risk. These positive samples came from 27 (79.4%) of the 34 selected public squares. Of the positive samples tested, Toxocara canis was the most common parasite found, with 27 positive samples, then Toxascaris leonina with 13 samples, Taenia spp with 10 samples, Giardia spp with 6 samples, hookworm with 4 samples, Cryptosporidium spp. with 2 samples and amebas with 1 sample spp. We conclude that a high percentage of public squares have dog feces with parasitic elements of scattering or resistance such as oocysts, cysts and eggs of zoonotic endoparasites which may pose a risk to public health.

Les parasites du genre Cryptosporidium comprennent des espèces infectant le tractus gastro-intestinal ou respiratoire d’un grand nombre de vertébrés y compris l'homme. Ces protistes intracellulaires sont les agents d’une zoonose cosmopolite à transmission oro-fécale, la cryptosporidiose. Au vu des travaux de notre laboratoire, nous savons à présent que Cryptosporidium parvum est également capable d’induire des néoplasies digestives chez un modèle murin SCID (Severe Combined Immunodeficiency mice), traitées ou pas par la dexaméthasone. Alors que C. muris, une autre espèce de Cryptosporidium, induit une infection chronique non associée à des transformations néoplasiques.Pour toutes ces raisons, il nous est apparu intéressant d’effectuer un travail de thèse articulé autour de trois axes principaux, l’épidémiologie, la transmission et la pathogénicité du parasite Cryptosporidium. Nous nous sommes intéressés dans un premier temps à l’épidémiologie moléculaire et la biodiversité génétique de Cryptosporidium dans des populations humaines de la région du Nord-Liban. Ceci nous a permis de mettre en évidence une prévalence de 5% de Cryptosporidium chez la population générale avec une prédominance de C. hominis. Ce qui constituait les premières données épidémiologiques de la cryptosporidiose au Liban. Ensuite d’autres études nous ont permis de montrer que cette prévalence pouvait atteindre même 10% chez les patients symptomatiques et les enfants.Dans un second temps, nous avons voulu étudier le mode de transmission du parasite et les facteurs de risque pouvant y être associés. Pour ce faire, une recherche du parasite a été réalisée aussi bien au Liban qu’en France chez des animaux d’élevage, sauvages, de compagnie et en captivité. Une première étude a été réalisée chez des patients et des bovins du Nord-Liban. L’ensemble des données rapportées nous permettent de suggérer un mode de transmission de la cryptosporidiose majoritairement anthroponotique au Liban, mais les résultats du génotypage ne permettent pas d’exclure la présence d’une transmission zoonotique. D’autres études réalisées en France, notamment sur des échantillons de selles collectées auprès des zoos de la Palmyre (à Royan) et de Lille ont montré un taux de prévalence de Cryptosporidium spp inférieur à 1%. Ces animaux ne semblent donc pas être un réservoir potentiel de cette infection. Alors que chez les poissons sauvages, nous avons pu identifier la présence entre autre de l’espèce zoonotique C. parvum dans l’estomac et l’intestin des poissons. Ceci nous permet de considérer les poissons comme étant une source de contamination potentiel pour l’homme, l’animal mais également pour l’environnement.Enfin le troisième axe avait pour but d’étudier la pathogénicité de ce parasite. Pour commencer nous avons voulu explorer les mécanismes de la cancérogénèse induite par la souche IOWA de C. parvum au niveau de la région iléocæcale des souris SCID traitées par la dexaméthasone (SCID-D). Pour ce faire nous nous sommes intéressés à quatre marqueurs de voies de signalisation cellulaires impliquées dans la survenue de cancers colorectaux (APC, Bêta-caténine, P53 et K‐ras). Nous avons ainsi pu montrer que la voie Wnt était impliquée dans ce processus. Ensuite nous avons voulu étudier l’association entre la pathologie cancéreuse et le parasitisme par Cryptosporidium chez l’homme. Une recherche du parasite a donc été réalisée dans des biopsies d’origines coliques et gastriques inclues en paraffine appartenant à des patients atteints ou non de cancers digestifs. Une différence significative a été rapportée entre la prévalence de la cryptosporidiose retrouvée chez la population de patients présentant des lésions cancéreuses (17%) et celle du groupe control constitué de patients non cancéreux mais présentant des symptômes (7%) p-value = 0.03. L’ensemble de ces données obtenues chez l’animal et chez l’homme montre que ce parasite a un impact important en santé humaine et animale. / Parasites of the genus Cryptosporidium comprise species infecting the gastrointestinal or respiratory tract of a wide variety of vertebrates including humans. These intracellular protists are the agents of a cosmopolitan zoonosis, with féco-oral transmission, cryptosporidiosis. Recent work from our laboratory, showed that the zoonotic species Cryptosporidium parvum is capable to induce digestive neoplasia in a SCID Severe Combined Immunodeficiency Mice (SCID) model, treated or not with dexamethasone. However C. muris, another species of Cryptosporidium, induces chronic infection in this rodent model but is not associated with neoplastic transformation.For all these reasons, it seemed interesting to carry out a thesis project articulated around three different axes: epidemiology, transmission and pathogenesis of the Cryptosporidium infection. We focused initially on the molecular epidemiology and genetic biodiversity of this parasite among human populations in North Lebanon. We found a Cryptosporidium prevalence of 5% among the general population, being C. hominis the predominant species. This prevalence could reach until 10% in symptomatic patients and children. This is the first epidemiological data about cryptosporidiosis in this country.Secondly, we studied the transmission routes and the main risk factors associated with the transmission of this parasite. To do this, a first study was conducted in parallel among animal populations in North Lebanon and France. The reported data suggest a predominance of an anthroponotic route of transmission for cryptosporidiosis in Lebanon, but the results of genotyping does not exclude the presence of zoonotic transmission. Other studies conducted in France, especially based on collection of stool samples in the zoos of Palmyre (Royan) and Lille showed that Cryptosporidium spp were present in less than 1% of captivity animals. The low prevalence strongly demonstrates that these animals play a negligible role as potential reservoirs of infection. While in wild fish, we could identify the presence of C. parvum, a zoonotic species, in the stomach and the gut of fish. These data suggest that the fish could be a natural host of C. parvum and a potential source of contamination for humans, animals but also for the environment.Finally, the third topic aimed to study the pathogenicity of this parasite. Firstly, we explored metabolic pathways potentially involved in the development of C. parvum-induced ileo-caecal oncogenesis in the SCID model treated with dexamethasone (SCID-D). We searched for alterations in genes or proteins commonly involved in cell cycle, differentiation or cell migration, such as β-catenin, Apc, E-cadherin, Kras and p53. We were able to show that the Wnt pathway was involved in this process. Finally, we wanted to study the association between digestive cancer and parasitism with Cryptosporidium in humans. Cryptosporidium molecular detection was therefore carried out in colonic and gastric biopsies belonging to patients with and without digestive cancers of recent diagnosis collected in North Lebanon. A statistically significant difference was observed between the prevalence of cryptosporidiosis found among the population of patients with digestive cancer (17%) and that of the control group consisting of non-cancer patients but with digestive symptoms (7%) (p-value = 0.03). All these data obtained in animals and humans strengthens the importance of this parasite in public health.