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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Characterization of reovirus-like agents associated with snakehead fish and cell culture

John, K. Riji January 1997 (has links)
No description available.
2

Studies on the comparative biology of Aphanomyces invadans

Lilley, James H. January 1997 (has links)
No description available.
3

Vector-pathogen interactions within the vector, Culicoides sonorensis

Mills, Mary Katherine January 1900 (has links)
Doctor of Philosophy / Division of Biology / Kristin Michel / The biting midge, Culicoides sonorensis, vectors orbiviruses of economic importance, such as epizootic hemorrhagic disease virus (EHDV). Due to the limitations in available molecular tools, critical Culicoides-orbivirus interactions underlying vector competence remain unclear. To provide a foundation for the study of midge-EHDV interactions, RNA interference (RNAi) was developed as a reverse genetic tool, and EHDV-2 infection dynamics were determined within C. sonorensis. To develop RNAi, exogenous double-stranded RNA (dsRNA) was injected into C. sonorensis adults specific to the C. sonorensis inhibitor of apoptosis protein 1 (CsIAP1) ortholog (dsCsIAP1). A significant decrease in CsIAP1 transcripts was observed in whole midges, with highest reduction in the midgut. In addition, dsCsIAP1-injected midges had increased mortality, a loss of midgut tissue integrity, and increased caspase activity. The longevity and midgut phenotypes were partially reversed by the co-injection of dsRNA specific to the C. sonorensis initiator caspase Dronc ortholog and CsIAP1. These results demonstrated that RNAi can be achieved in the midge midgut through injection of target dsRNAs into the hemolymph. Furthermore, the time course of EHDV-2 infection within C. sonorensis was characterized. EHDV-2 infection was observed in the midgut and secondary tissues, including the salivary glands, by 5 days post-feeding (dpf). These data are consistent with dissemination of EHDV-2 to secondary susceptible tissues throughout the midge via the hemolymph and indicate that virus transmission by C. sonorensis may occur as early as 5 dpf. This work provides a foundation for the future study of Culicoides-orbivirus interactions, including the antiviral role of RNAi at the midgut barrier.
4

Role of intestinal dysbiosis on gut colonization by bacterial pathogens

Djukovic, Ana 03 November 2017 (has links)
The intestinal tract of virtually any metazoan, including mammals, is colonized with a complex microbial community to which we refer as intestinal or gut microbiota. One of the roles of the healthy intestinal microbiota is to protect the host against gut colonization with pathogenic bacteria through a phenomenon known as colonization resistance (CR). Dysbiosis of the intestinal microbiota, usually as a result of an antibiotic treatment, may lead to the disruption of the CR, and subsequent colonization with bacterial pathogens. However, and despite the importance, the role of the microbiota dysbiosis on the gut colonization by many bacterial pathogens, such as multidrug resistant Enterobacteriaceae, has not been elucidated: the members of the microbiota that confer CR and factors that promote colonization remain mostly unknown. The general aim of this thesis has been to improve the understanding of the role of the microbiota dysbiosis in gut colonization by bacterial pathogens. For this purpose, 3 projects have been established. In the first project we tried to elucidate the role of the microbiota dysbiosis on colonization by multidrug resistant Enterobacteriaceae (MRE) in mice. In the second project we investigated the risk factors and members of the microbiota associated with the MRE colonization in hospitalized patients. MRE infections represent a great threat for hospitalized patients. Specifically, acute leukemia patients are often colonized with MRE, probably due to the impaired CR as a result of intensive antibiotic treatments these patients receive. In the third project we studied the role of the microbiota dysbiosis on the development of Epizootic Rabbit Enteropathy (ERE). ERE is a severe gastrointestinal disease with a high percentage of mortality that occurs in young rabbits during first weeks post-weaning. ERE rabbits have been shown to suffer microbiota dysbiosis during the development of the disease. Moreover, the disease could be reproduced by contact between healthy and sick animals and by administration of cecal contents from ERE rabbits to healthy rabbits, suggesting that a pathogenic agent may be involved in the development of this intestinal pathology, although no causative agent has been identified until now. / El tracto intestinal de prácticamente cualquier metazoo, incluidos los mamíferos, está colonizado por una compleja comunidad microbiana a la que nos referimos como microbiota intestinal. Uno de los papeles de la microbiota intestinal es proteger al huésped contra la colonización intestinal con bacterias patógenas a través de un fenómeno conocido como resistencia a la colonización (RC). La disbiosis de la microbiota intestinal, a menudo como resultado de un tratamiento antibiótico, puede conducir a la alteración de la RC y posterior colonización por patógenos bacterianos. Sin embargo, y pese a su importancia, el papel de la disbiosis de la microbiota en la colonización intestinal por muchos patógenos bacterianos, como son las Enterobacterias multirresistentes, no se ha esclarecido: los miembros de la microbiota que confieren RC y los factores que promueven la colonización siguen siendo desconocidos. El objetivo general de esta tesis ha sido mejorar la comprensión del papel de disbiosis de la microbiota en la colonización intestinal por patógenos bacterianos. Para ello se han establecido tres proyectos. En el primer proyecto investigamos el papel de disbiosis de la microbiota intestinal en la colonización por Enterobacterias multiresistentes (MRE) en ratones. En el segundo proyecto investigamos los factores de riesgo y los miembros de la microbiota asociados con la colonización por MRE en pacientes hospitalizados. Las infecciones por MRE representan una gran amenaza para los pacientes hospitalizados. Específicamente, MRE a menudo colonizan los pacientes con leucemia aguda, probablemente debido a que la RC está alterada como resultado de tratamientos antibióticos intensivos recibidos por estos pacientes. En el tercer proyecto investigamos el papel de la disbiosis microbiana en desarollo de Enteropatía Epizoótica de Conejo (ERE). ERE es una enfermedad gastrointestinal severa con un alto porcentaje de mortalidad que ocurre en conejos jóvenes durante las primeras semanas después del destete. Se ha demostrado que los conejos con ERE sufren disbiosis microbiana después del inicio de la enfermedad, aunque no está claro el papel de la disbiosis en el desarollo de la enfermedad. Además, la enfermedad puede ser reproducida por contacto entre animales sanos y enfermos y por la administración del contenido cecal de conejos con ERE a conejos sanos, lo que sugiere que un agente patógeno podría estar implicado en el desarrollo de esta patología intestinal, aunque hasta ahora no se ha logrado identificar ningún agente causal. / El tracte intestinal de pràcticament qualsevol metazoo, inclosos els mamífers, està colonitzat per una complexa comunitat microbiana a la qual ens referim com microbiota intestinal. Un dels papers de la microbiota intestinal és protegir a l'hoste contra la colonització intestinal amb bacteris patògens a través d'un fenomen conegut com a resistència a la colonització (RC). La disbiosis de la microbiota intestinal, frecuentment com a resultat d'un tractament antibiòtic, pot conduir a l'alteració de la RC i posterior colonització per patògens bacterians. No obstant això, i malgrat la seva importància, el paper de la disbiosis de la microbiota en la colonització intestinal per molts patògens bacterians, com són les Enterobacteries multirresistentes, no s'ha esclarit: els membres de la microbiota que confereixen RC i els factors que promouen la colonització segueixen sent desconeguts. L'objectiu general d'aquesta tesi ha estat millorar la comprensió del paper de la disbiosis de la microbiota en la colonització intestinal per patògens bacterians. Per a això s'han establert tres projectes. En el primer projecte vam investigar el paper de la disbiosis de la microbiota intestinal en la colonització per Enterobacteries multiresistentes (MRE) en ratolins. En el segon projecte, investiguem els factors de risc i els membres de la microbiota associats amb la colonització per MRE en pacients hospitalitzats. Les infeccions per MRE representen una gran amenaça per als pacients hospitalitzats. Específicament, MRE sovint colonitza els pacients amb leucèmia aguda, probablement a causa de que la RC està alterada com a resultat de tractaments antibiòtics intensius rebuts per aquests pacients. En el tercer projecte, vam investigar el paper de la disbiosis microbiana en desenvolupament de l'Enteropatía Epizoótica de Conill (ERE). ERE és una malaltia gastrointestinal severa amb un alt percentatge de mortalitat que ocorre en conills joves durant les primeres setmanes després del deslleti. S'ha demostrat que els conills amb ERE sofreixen disbiosis microbiana després de l'inici de la malaltia, encara que no és clar el paper de la disbiosis en el desenvolupament de la malaltia. A més, la malaltia pot ser reproduïda per contacte entre animals sans i malalts i per l'administració del contingut cecal de conills amb ERE a conills sans, la qual cosa suggereix que un agent patogen podria estar implicat en el desenvolupament d'aquesta patologia intestinal, encara que fins ara no s'ha aconseguit identificar cap agent causal. / Djukovic, A. (2017). Role of intestinal dysbiosis on gut colonization by bacterial pathogens [Tesis doctoral no publicada]. Universitat Politècnica de València. doi:10.4995/Thesis/10251/90415 / TESIS
5

Modeling the Role of Land-Use Change on the Spread of Infectious Disease

January 2020 (has links)
abstract: Land-use change has arguably been the largest contributor to the emergence of novel zoonotic diseases within the past century. However, the relationship between patterns of land-use change and the resulting landscape configuration on disease spread is poorly understood as current cross-species disease transmission models have not adequately incorporated spatial features of habitats. Furthermore, mathematical-epidemiological studies have not considered the role that land-use change plays in disease transmission throughout an ecosystem. This dissertation models how a landscape's configuration, examining the amount and shape of habitat overlap, contributes to cross-species disease transmission to determine the role that land-use change has on the spread of infectious diseases. To approach this, an epidemiological model of transmission between a domesticated and a wild species is constructed. Each species is homogeneously mixed in its respective habitat and heterogeneously mixed in the habitat overlap, where cross-species transmission occurs. Habitat overlap is modeled using landscape ecology metrics. This general framework is then applied to brucellosis transmission between elk and cattle in the Greater Yellowstone Ecosystem. The application of the general framework allows for the exploration of how land-use change has contributed to brucellosis prevalence in these two species, and how land management can be utilized to control disease transmission. This model is then extended to include a third species, bison, in order to provide insight to the indirect consequences of disease transmission for a species that is situated on land that has not been converted. The results of this study can ultimately help stakeholders develop policy for controlling brucellosis transmission between livestock, elk, and bison, and in turn, could lead to less disease prevalence, reduce associated costs, and assist in population management. This research contributes novelty by combining landscape ecology metrics with theoretical epidemiological models to understand how the shape, size, and distribution of habitat fragments on a landscape affect cross-species disease transmission. The general framework demonstrates how habitat edge in single patch impacts cross-species disease transmission. The application to brucellosis transmission in the Greater Yellowstone Ecosystem between elk, cattle, and bison is original research that enhances understanding of how land conversion is associated with enzootic disease spread. / Dissertation/Thesis / Doctoral Dissertation Applied Mathematics for the Life and Social Sciences 2020
6

Serological and genetic characterisation of putative new serotypes of bluetongue virus and epizootic haemorrhagic disease virus isolated from an Alpaca / Isabella Maria Wright

Wright, Isabella Maria January 2014 (has links)
Alpacas were first introduced into South Africa during the year 2000. They are valuable because of the fine quality wool they produce which has much better insulation properties than that of merino wool fibres. Alpacas are also used to act as guards of sheep herds against predators. During 2008, blood samples from an alpaca that died acutely with severe lung oedema, respiratory distress and froth exuding from the nose were received at Elsenburg Veterinary Laboratory. The alpaca was from a herd of 23 alpacas of a British veterinarian in the Montagu district in the western Cape. Virus isolation attempts on the blood produced infrequent embryo mortalities. Embryonated chicken egg (ECE) material was send to the Virology Department at the Onderstepoort Veterinary Institute (OVI). A bluetongue virus (BTV) PCR performed at the diagnostic PCR laboratory at OVI on the ECE material was positive. Further intra-venous (IV) inoculations in ECE produced embryo mortalities on two consecutive days, the 8th and 9th November. The dead embryos were harvested separately and named and treated as two separate virus samples, Alp8 and Alp9 which were further passaged on baby hamster kidney (BHK) cells. The BTV virus neutralisation tests (VNT) performed at the Office International des Epizooties (OIE) Laboratory on both Alp8 and Alp9 were negative. Because of the close serological relationship between BTV and epizootic haemorrhagic disease virus (EHDV), an EHDV VNT was also performed and was also negative. In the light of the negative VNT and the positive BTV PCR results, more in-depth molecular analyses were performed. RNA was purified from tissue culture material and agarose gel electrophoresis (AGE) performed. Both Alp8 and Alp9 had a typical orbiviral electrophoretic profile, but their respective profiles were different. A sequence-independent reverse transcriptase PCR amplification method generated ample complementary DNA (cDNA) of both samples for sequencing. Sanger sequencing was used to partially sequence genome segments 5 (NS1) and 2 (VP2). BLAST analysis of the partial information of the genome segments 5 (NS1) of Alp8 confirmed it as being a BTV and Alp9 as being an EHDV. BLAST analysis of the deduced amino acid sequence generated of VP2 of both Alp8 and Alp9 established that these samples were possibly new serotypes of BTV and EHDV respectively. The complete genome of both Alp8 and Alp9 was sequenced with next generation 454 Pyrosequencing. This confirmed the partial sequencing results. BLAST analysis of the complete sequence of S2 (VP2) of Alp8 showed that it has 73 % nucleotide and 77 % deduced amino acid identity to BTV15. In contrast the nucleic acid sequence of genome segment S2 (VP2) of Alp9 had no nucleotide sequence identity to any virus, but its deduced amino acid sequence had 71 % amino acid identity to EHDV2. Hyper immune guinea pig (GP) serum prepared against the putative new BT (Alp8) and EHD (Alp9) virus serotypes were tested for serological cross-reactivity against the 24 OIE reference antigen strains of BTV and the 8 OIE reference antigen strains of EHDV. Alp8 had a neutralising antibody (NAb) titre of > 32 against BTV15. Alp9 did not cross react with any of the OIE BTV and EHDV strains. Six out of the remaining 22 alpacas on the farm had NAbs to a greater or lesser extend against Alp8 (BTV) and Alp9 (EHDV) viruses, which confirmed that the viruses were also present in other alpacas in the herd. Very few cases of EHDV in alpacas have ever been reported in literature. A small scale pilot vector susceptibility study showed that vector competence of C. imicola for both Alp8 and Alp9 was low, below 2 %. The fact that neutralising antibodies to Alp8 and Alp9 were detected in other alpacas in the herd raises the question as to whether there are other Culicoides species circulating in the area that could vector the viruses. In conclusion, the results from the serological and virological analyses as well as the nucleic acid sequence data of the genomes of two virus samples, Alp8 and Alp9, from an alpaca that died in the Montagu district in the western Cape identified Alp9 as a definite new serotype of EHDV and Alp8 as a possible new serotype of BTV most closely related to BTV15. / MSc (Biochemistry), North-West University, Potchefstroom Campus, 2014
7

Serological and genetic characterisation of putative new serotypes of bluetongue virus and epizootic haemorrhagic disease virus isolated from an Alpaca / Isabella Maria Wright

Wright, Isabella Maria January 2014 (has links)
Alpacas were first introduced into South Africa during the year 2000. They are valuable because of the fine quality wool they produce which has much better insulation properties than that of merino wool fibres. Alpacas are also used to act as guards of sheep herds against predators. During 2008, blood samples from an alpaca that died acutely with severe lung oedema, respiratory distress and froth exuding from the nose were received at Elsenburg Veterinary Laboratory. The alpaca was from a herd of 23 alpacas of a British veterinarian in the Montagu district in the western Cape. Virus isolation attempts on the blood produced infrequent embryo mortalities. Embryonated chicken egg (ECE) material was send to the Virology Department at the Onderstepoort Veterinary Institute (OVI). A bluetongue virus (BTV) PCR performed at the diagnostic PCR laboratory at OVI on the ECE material was positive. Further intra-venous (IV) inoculations in ECE produced embryo mortalities on two consecutive days, the 8th and 9th November. The dead embryos were harvested separately and named and treated as two separate virus samples, Alp8 and Alp9 which were further passaged on baby hamster kidney (BHK) cells. The BTV virus neutralisation tests (VNT) performed at the Office International des Epizooties (OIE) Laboratory on both Alp8 and Alp9 were negative. Because of the close serological relationship between BTV and epizootic haemorrhagic disease virus (EHDV), an EHDV VNT was also performed and was also negative. In the light of the negative VNT and the positive BTV PCR results, more in-depth molecular analyses were performed. RNA was purified from tissue culture material and agarose gel electrophoresis (AGE) performed. Both Alp8 and Alp9 had a typical orbiviral electrophoretic profile, but their respective profiles were different. A sequence-independent reverse transcriptase PCR amplification method generated ample complementary DNA (cDNA) of both samples for sequencing. Sanger sequencing was used to partially sequence genome segments 5 (NS1) and 2 (VP2). BLAST analysis of the partial information of the genome segments 5 (NS1) of Alp8 confirmed it as being a BTV and Alp9 as being an EHDV. BLAST analysis of the deduced amino acid sequence generated of VP2 of both Alp8 and Alp9 established that these samples were possibly new serotypes of BTV and EHDV respectively. The complete genome of both Alp8 and Alp9 was sequenced with next generation 454 Pyrosequencing. This confirmed the partial sequencing results. BLAST analysis of the complete sequence of S2 (VP2) of Alp8 showed that it has 73 % nucleotide and 77 % deduced amino acid identity to BTV15. In contrast the nucleic acid sequence of genome segment S2 (VP2) of Alp9 had no nucleotide sequence identity to any virus, but its deduced amino acid sequence had 71 % amino acid identity to EHDV2. Hyper immune guinea pig (GP) serum prepared against the putative new BT (Alp8) and EHD (Alp9) virus serotypes were tested for serological cross-reactivity against the 24 OIE reference antigen strains of BTV and the 8 OIE reference antigen strains of EHDV. Alp8 had a neutralising antibody (NAb) titre of > 32 against BTV15. Alp9 did not cross react with any of the OIE BTV and EHDV strains. Six out of the remaining 22 alpacas on the farm had NAbs to a greater or lesser extend against Alp8 (BTV) and Alp9 (EHDV) viruses, which confirmed that the viruses were also present in other alpacas in the herd. Very few cases of EHDV in alpacas have ever been reported in literature. A small scale pilot vector susceptibility study showed that vector competence of C. imicola for both Alp8 and Alp9 was low, below 2 %. The fact that neutralising antibodies to Alp8 and Alp9 were detected in other alpacas in the herd raises the question as to whether there are other Culicoides species circulating in the area that could vector the viruses. In conclusion, the results from the serological and virological analyses as well as the nucleic acid sequence data of the genomes of two virus samples, Alp8 and Alp9, from an alpaca that died in the Montagu district in the western Cape identified Alp9 as a definite new serotype of EHDV and Alp8 as a possible new serotype of BTV most closely related to BTV15. / MSc (Biochemistry), North-West University, Potchefstroom Campus, 2014
8

Studies on host responses to Aphanomyces invadans

Miles, David J. C. January 2002 (has links)
Aphanomyces invadans is the pathogen that causes epizootic ulcerative syndrome (EUS), an economically devastating fish disease in southern Asia. The present thesis considered possible improvements to current methods of monitoring EUS, and examined the mechanisms of the host immune response to A. invadans in order to establish whether they could be enhanced to reduce the impact of EUS on aquaculture. Monoclonal antibody (MAb) technology was considered as a possible improvement to the histopathological methods currently used in diagnosis of EUS. Five MAbs were raised to day-old A. invadans germlings. Four gave weak reactions to A. invadans and cross-reacted with other Aphanomyces spp, though they may be useful for future studies on A. invadans. The other, designated MAb 3gJC9, only cross-reacted with the crayfish plague pathogen, A. astaci, and was used for the development of an immunohistochemistry protocol that may be of use in diagnosis. Immunohistochemistry with MAb 3gJC9, which recognised an extracellular product (ECP) of A. invadans, was specific to A. invadans in fish tissue, although it also recognised A. astaci in plague-infected crayfish. It also recognised the mycelium in fish infected with ulcerative mycosis, indicating that ulcerative mycosis is synonymous with EUS. Preliminary observations indicated that both ECPs and what appeared to be a hitherto unreported early stage of the mycelium are important in the pathology of EUS. Studies in vitro on the macrophages of EUS-susceptible giant gourami Osphronemus gouramy and silver barb Barbodes gonionotus, and EUS-resistant Nile tilapia Oreochromis niloticus, found that their macrophages were able to inhibit the growth of A. invadans. The macrophages of striped snakehead Channa striata did not inhibit A. invadans, which may account for their high EUS-susceptibility, especially as A. invadans strongly inhibited the respiratory burst of snakehead macrophages. Studies on humoral immune responses revealed that complement inhibited A. invadans in the case of snakeheads, gourami and barbs but not tilapia or swamp eels Monopterus albus. The humoral responses of the latter were very different to the four other species, and not elucidated. Low levels of anti A. invadans antibodies were found in tilapia and gourami from an EUS-endemic region, and high levels in snakehead. Snakehead antibodies appeared to be able to inhibit A. invadans even when complement was removed, but lower levels were produced at the low temperatures typically associated with EUS. A range of potential immunostimulants were screened for the ability to enhance resistance to EUS. The two successful products were administered as feed supplements to snakeheads and barbs that were subsequently injected intramuscularly with A. invadans. One, the algal extract Ergosan, showed some beneficial effects on snakeheads although the challenge was inconclusive. The other, the vitamin supplement Salar-bec, accelerated the cellular immune response and reduced mortality in snakeheads and barbs, and enhanced antibody production in snakeheads. The antibody response of snakeheads was further studied by comparing the anti- A. invadans antibody level, inhibitory activity of sera in vitro and protective capacity of sera from EUS-naïve snakeheads to that of snakeheads recently exposed to EUS and those subject to long term EUS-exposure. Sera of populations recently exposed to EUS showed an increased level of antibodies, but little improvement in inhibitory or protective activity. Sera from snakeheads that had endured long term exposure showed a wide range of antibody levels, but marked increases in inhibitory and protective activity. Antibodies cross-reacted with non-pathogenic Aphanomyces spp. in all cases.
9

Analýza zásahů vyčleněných prostředků ozbrojených sil ČR / Analysis of interventions of detached units from Czech Armed Forces

Kopecká, Jana January 2013 (has links)
Title: Analysis of interventions of detached units from Czech Armed Forces Objectives of work: to make overview of interventions of Czech Armed Forces for Integrated rescue system in the period 2001-2010 and divided by the nature of the emergencies. The results will be analysed in order to make conclusions in five areas: 1. overall use of Czech Armed Forces for Integrated rescue system 2. factors limiting use of Czech Armed Forces for Integrated rescue system 3. strengths and weaknesses in the internal management of Czech Armed Forces during deployment 4. cooperation of Czech Armed Forces and Integrated rescue system including a focus on functionality of established principles and algorithms required to deploy forces and equipment of Czech Armed Forces to rescue or liquidation operations. 5. financial costs of interventions of Czech Armed Forces for Integrated rescue system Method: Search in literature and writing the results in logical order. Procedures of reduced PEST analysis are used to assess the general risks of environment in the Czech Republic. The analytical part is processed with the help of elements of system analysis. Keywords: Integrated rescue system, Czech Arrned forces, natural disasters, epizootic, anthropogenic emergencies.

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