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Harrison, Eleanor Margaret. "Epidemiology and evolution of vector borne disease." Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619145.
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In recent years the incidence of many vector borne-diseases has increased worldwide. We investigate the epidemiology and evolution of vector-borne disease, focussing on the neglected tropical disease leishmaniasis to determine suitable strategies for control and prevention. We develop a compartmental mathematical model for leishmaniasis, and examine the dependence of disease spread on model parameters. We perform an elasticity analysis to establish the relative impact of disease parameters and pathways on infection spread and prevalence. We then use optimal control theory to determine optimal vaccination and spraying strategies for leishmaniasis, and assess the dependence of control on disease relapse. We investigate the evolution of virulence in vector-borne disease using adaptive dynamics and both non-spatial and metapopulation models for disease spread. Using our metapopulation model we also determine the impact of land-use change such as urbanisation and deforestation on disease spread and prevalence. We find that in the absence of evolution, control techniques which directly reduce the rate of vector transmission lead to the greatest reduction in potential disease spread. Although the spraying of insecticide can reduce the basic reproductive number $R_{0}$, we find that vaccination is more effective. Disease relapse is the driving force behind infection at endemic equilibrium and greatly increases the level of control required to prevent a disease epidemic. When a trade-off is in place between transmission and virulence we find that control techniques which reduce the duration of transmission lead to the fixation of pathogen strains with heightened virulence. Control techniques such as spraying can therefore be counterproductive, as increasing virulence increases human infection prevalence. This holds true when virulence is in either the host or vector and suggests that virulence within the vector should not be ignored. Urbanisation and deforestation can also lead to increases in both transmission and virulence, as reducing the distance between urban settlements and the vector natural habitat alters disease incidence.
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Morin, Cory William. "Climate and Environmental Influences on the Ecology of Vectors and Vector-borne Diseases." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/241951.
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Recently researchers have recognized the potential effects of climate variability and climate change on infectious disease ecology. Mosquito-borne diseases are of considerable concern due to their reliance on temperature to regulate vector reproduction, survival, and vector and agent development. Precipitation is also influential because it helps maintain habitat for immature mosquitoes. The interactions between climate, vector, and agent are complex, however, and thus assessing the overall impact of climate on disease occurrence is difficult. Discerning the influence of climate on mosquito-borne diseases requires an interdisciplinary synthesis of knowledge about the relationships between components of the disease system and analysis techniques that account for the individual and interacting roles that each element contributes to the ecology of the disease. In this dissertation, climate and climate change influences on dengue fever and West Nile virus are identified through process based modeling to simulate changes in vector and viral transmission dynamics. Analysis of the literature pertaining to climate influences on dengue virus ecology reveals that climate variables often interact interdependently to influence dengue virus transmission. Statistical techniques correlating or modeling climate-dengue relationships are often inconsistent and location specific. Process based modeling has been employed to better simulate the intricacies and non-linear dynamics involved, but most models focus only on vector populations. Therefore, models should incorporate viral development and transmission components to better simulate dengue virus ecology. A model of West Nile virus vector dynamics across the southern United States reveals that impacts from climate change are very location and context-specific. While temperatures generally increase the season length of vector activity, changes in precipitation and evapotranspiration dynamics often lead to lower summer mosquito populations and limited population development in water-stressed areas. A simulation of dengue fever cases in San Juan County, Puerto Rico with a coupled vector-epidemiological model showed strong agreement when compared with reported case data (Willmott's d = 0.90 and r2 = 0.71). The model indicates that certain climate variables became disease limiting during specific times of the year. Temperature limits virus transmission during the winter by slowing viral development while lower precipitation limits spring transmission by suppressing vector populations.
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El, Moustaid Fadoua. "Modeling Temperature Effects on Vector-Borne Disease Dynamics." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/102579.
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Vector-borne diseases (VBDs) cause significant harm to humans, plants, and animals worldwide. For instance, VBDs are very difficult to manage, as they are governed by complex interactions. VBD transmission depends on the pathogen itself, vector-host movement, and environmental conditions. Mosquito-borne diseases are a perfect example of how all these factors contribute to changes in VBD dynamics. Although vectors are highly sensitive to climate, modeling studies tend to ignore climate effects. Here, I am interested in the arthropod small vectors that are sensitive to climate factors such as temperature, precipitation, and drought. In particular, I am looking at the effect of temperature on vector traits for two VBDs, namely, dengue, caused by a virus that infects humans and bluetongue disease, caused by a virus that infects ruminants. First, I collect data on mosquito traits' response to temperature changes, this includes adult traits as well as juvenile traits. Next, I use these traits to model mosquito density, and then I incorporate the density into our mathematical models to investigate the effect it has on the basic reproductive ratio R0, a measure of how contagious the disease is. I use R0 to determine disease risk. For dengue, my results show that using mosquito life stage traits response to temperature improves our vector density approximation and disease risk estimates. For bluetongue, I use midge traits response to temperature to show that the suitable temperature for bluetongue risk is between 21.5 �C and 30.7 �C. These results can inform future control and prevention strategies.Doctor of Philosophy
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Uzcategui, Cuello Nathalie Yumari. "Evolution and dispersal of mosquito-borne flaviviruses." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288520.
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Costa, Maria Carolina Regateiro Machado e. "Vector-borne pathogens found in carnivores in wild Namibia." Master's thesis, Universidade de Lisboa, Faculdade de Medicina Veterinária, 2019. http://hdl.handle.net/10400.5/18037.
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Dissertação de Mestrado Integrado em Medicina VeterináriaThis dissertation aimed to identify and molecularly characterize vector-borne pathogens from several parasite families, all possessing stages found in peripheral blood, from a wide variety of free-ranging carnivores living in Namibia, in the southern part of Africa. Blood samples collected from 9 bat-eared foxes (Otocyon megalotis), 17 brown hyenas (Parahyaena brunnea), 19 spotted hyenas (Crocuta crocuta) and 85 cheetahs (Acinonyx jubatus) were screened by Polymerase Chain Reactions (PCRs) and tested for pathogens of the Onchocercidae family, the order Piroplasmida, bacteria from the Anaplasmataceae and the Rickettsiaceae families and, lastly, the Hepatozoidae family. The PCRs targeted both the ITS-2 and 12S, 18S, 16S, 18S and 18S rRNA genes respectively and were followed by nucleotide sequencing. In total, sampled animals showed a 43.1% rate of Onchocercidae infection, 67.7% of Piroplasmida, 60% of them were positive for Anaplasmataceae, 10% for Rickettsiaceae and Hepatozoidae were detected in 47.7% of them. Obtained filaroid sequences showed high homologies with both Acanthocheilonema reconditum and Acanthocheilonema dracunculoides and further phylogenetic analysis were performed in both brown and spotted hyenas, with the construction of a phylogenetic tree. Piroplasmida results were not studied any further. For Anaplasmataceae, subsequent sequencing results indicated high similarity with both Anaplasma phagocytophilum and Anaplasma platys and varied PCR protocols were conducted in order to differentiate between these organisms, but no conclusions were reached. The Rickettsiaceae found displayed high homologies with Rickettsia raoultii. And finally, the Hepatozoidae infection showed to be a mixed one with both Hepatozoon canis and Hepatozoon felis. These results are important not only on a conservation level for the infected host species, but are also relevant for domestic animals coexisting in the surrounding areas, as well as humans, especially since a few of the parasites found may have zoonotic potential. Future studies should focus on understanding vectors, transmission routes, infection dynamics and host specificity in order to better evaluate the possible danger these infections may withhold.
RESUMO - Agentes patogénicos transmitidos por vetores presentes em carnívoros na Namíbia - Esta dissertação teve como principal objetivo identificar e caracterizar molecularmente agentes patogénicos transmitidos por vetores de várias famílias parasitárias, com o aspeto em comum de todas possuírem fases do desenvolvimento encontradas no sangue, de espécies variadas de carnívoros selvagens que habitam na Namíbia, no Sul de África. Foram testadas amostras sanguíneas de 9 raposas-orelhas-de-morcego (Otocyon megalotis), 17 hienas-castanhas (Parahyaena brunnea), 19 hienas-malhadas (Crocuta crocuta) e 85 chitas (Acinonyx jubatus) por PCR e analisadas para pesquisa de parasitas da família Onchocercidae, da ordem Piroplasmida, bactérias das famílias Anaplasmataceae e Rickettsiaceae e, finalmente, da família Hepatozoidae. Os PCRs foram direcionados aos genes do rRNA ITS-2 e 12S, 18S, 16S, 18S e 18S respetivamente e foram seguidos de sequenciação de nucleótidos. Na totalidade, os animais testados mostraram uma taxa de infeção de 43.1% por Onchocercidae, de 67.7% de Piroplasmida, 60% deles tiveram resultados positivos para Anaplasmataceae, 10% para Rickettsiaceae e Hepatozoidae foram detetados em 47.7% da população. As sequências obtidas de filarídeos, mostraram possuir elevadas homologias com Acanthocheilonema reconditum e Acanthocheilonema dracunculoides, e estudos filogenéticos mais intensivos foram realizados, nomeadamente uma árvore filogenética que inclui ambas as espécies de hienas. Os resultados relativos a Piroplasmida não foram aprofundados. Para as Anaplasmataceae, as sequenciações subsequentes indicaram elevada similaridade com Anaplasma phagocytophilum e Anaplasma platys e múltiplos protocolos de PCRs foram efetuados, com o intuito de diferenciar entre estas duas espécies, mas não foram retiradas quaisquer conclusões. As Rickettsiaceae presentes evidenciaram fortes semelhanças com Rickettsia raoultii. E finalmente, as infeções por Hepatozoidae mostraram ser uma infeção mista por ambos Hepatozoon canis e Hepatozoon felis. A importância destes resultados não se limita apenas à conservação das espécies animais em causa, mas são também relevantes em termos dos animais domésticos coabitantes na mesma região, assim como humanos, especialmente tendo em conta o possível potencial zoonótico de algumas espécies parasitárias. Estudos futuros devem ter como principais objetivos o estudo dos vetores respetivos, tipo de transmissão, dinâmica da infeção e especificidade parasitária, para melhor avaliar os possíveis perigos que podem advir da presença destes parasitas.
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McOdimba, Francis Awuor. "Epidemiology of vector-borne diseases in cattle from SE Uganda." Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/30498.
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Institutions involved in vector-borne diseases research, epidemiological studies as well as vaccine development require reliable and sensitive assays to support the development of vaccine products and new drugs for treatment. These diagnostic assays also aid in identifying disease control target populations, and to monitor infection during trials for assessing the efficacy of preventive or curative drug. Molecular techniques such as the polymerase chain reaction (PCR) amplification have been used in detecting parasites of several species, sub-species and types and are favoured over microscopic examination of blood or the immunological methods because of their superior sensitivity and higher throughput. Two of the most commonly used diagnostic methods, microscopy and molecular techniques for pathogen detection and species characterization, were evaluated for their sensitivity and specificity and subsequently used in screening cattle for parasites in the blood of cattle kept under traditional mixed farming management system. Molecular methods revealed higher VBD prevalence in the cattle from the villages of Tororo and Busia districts of SE Uganda. The prevalence of trypanosome species pathogenic to livestock was found to be higher than previously documented in this area. Based on the data obtained by PCR amplification the effect of prophylactic drug intervention against trypanosomiasis was assessed over a period of six months. While isometamidium chloride treatment of cattle appeared to control trypanosomiasis in areas with low prevalence, the drug had no effect in controlling the disease in high prevalence areas. It would therefore be necessary to combine the use of drug intervention with other methods such as vector control, to reduce the prevalence, in order to realize effective control of trypanosomiasis.
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Shearer, Freya. "Improving geospatial models of risk for vector-borne, zoonotic diseases." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:cfe8ffa9-453b-4e10-9009-e387a39db6de.
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Public health surveillance data are often incomplete, particularly where resources are lacking, but geospatial models can help to fill the gaps by providing estimates where data are sparse. By combining information on locations where diseases have been recorded with geographic data on environmental and socioeconomic covariates known to affect disease transmission using machine-learning models (such as boosted regression trees), niche modelling can generate fine-resolution, evidence-based risk maps for a variety of diseases of public health importance. This thesis investigates the geographical distribution of two vector-borne, zoonotic diseases of public health importance: Plasmodium knowlesi malaria and yellow fever (YF). A number of new methodological approaches to niche modelling are developed for: mapping diseases whose distributions are impacted by multiple host and vector species, ameliorating spatial bias in disease reporting rates, and accounting for human vaccination coverage. Chapter 2 investigates spatial variation in risk of human P. knowlesi infection across Southeast Asia. The infection risk model for P. knowlesi malaria is based on improvements to a standard niche modelling approach, and incorporates a novel joint distribution model to leverage data from a number of host species. Chapter 3 estimates YF vaccination coverage through time across all age cohorts in every district/municipality of countries at risk of YF, globally. These estimates are used to estimate the additional vaccination coverage needed to prevent further YF outbreaks, and they provide information needed to account for population immunity when estimating YF infection risk. Chapter 4 describes the development of a novel Poisson point process niche model, which is then used to predict YF infection risk in humans and demonstrates how vaccination coverage can be efficiently accounted for in disease niche models. The disease risk maps of P. knowlesi malaria and YF produced through this thesis will act as resources to improve the targeting, implementation and evaluation of disease prevention, surveillance and control strategies. Methods developed to account for vaccination coverage, reporting rate biases, and complex transmission systems will be applicable to risk mapping for a range of vector-borne, zoonotic diseases of public health importance.
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Xue, Ling. "Modeling and analysis of vector-borne diseases on complex networks." Diss., Kansas State University, 2013. http://hdl.handle.net/2097/16788.
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Doctor of PhilosophyDepartment of Electrical and Computer Engineering
Caterina Scoglio
Vector-borne diseases not only cause devastating economic losses, they also significantly impact human health in terms of morbidity and mortality. From an economical and humane point of view, mitigation and control of vector-borne diseases are essential. Studying dynamics of vector-borne disease transmission is a challenging task because vector-borne diseases show complex dynamics impacted by a wide range of ecological factors. Understanding these factors is important for the development of mitigation and control strategies. Mathematical models have been commonly used to translate assumptions concerning biological (medical, demographical, behavioral, immunological) aspects into mathematics, linking biological processes of transmission and dynamics of infection at population level. Mathematical analysis translates results back into biology. Classical deterministic epidemic models do not consider spatial variation, assuming space is homogeneous. Spatial spread of vector-borne diseases observed many times highlights the necessity of incorporating spatial dynamics into mathematical models. Heterogeneous demography, geography, and ecology in various regions may result in different epidemiological characteristics. Network approach is commonly used to study spatial evolution of communicable diseases transmitted among connected populations. In this dissertation, the spread of vector-borne diseases in time and space, is studied to understand factors that contribute to disease evolution. Network-based models have been developed to capture different features of disease transmission in various environments. Network nodes represent geographical locations, and the weights represent the level of contact between regional pairings. Two competent vector populations, Aedes mosquitoes and Culex mosquitoes, and two host populations, cattle and humans were considered. The deterministic model was applied to the 2010 Rift Valley fever outbreak in three provinces of South Africa. Trends and timing of the outbreak in animals and humans were reproduced. The deterministic model with stochastic parameters was applied to hypothetical Rift Valley fever outbreak on a large network in Texas, the United States. The role of starting location and size of initial infection in Rift Valley fever virus spread were studied under various scenarios on a large-scale network. The reproduction number, defined as the number of secondary infections produced by one infected individual in a completely susceptible population, is typically considered an epidemic threshold of determining whether a disease can persist in a population. Extinction thresholds for corresponding Continuous-time Markov chain model is used to predict whether a disease can perish in a stochastic setting. The network level reproduction number for diseases vertically and horizontally transmitted among multiple species on heterogeneous networks was derived to predict whether a disease can invade the whole system in a deterministic setting. The complexity of computing the reproduction number is reduced because the expression of the reproduction number is the spectral radius of a matrix whose size is smaller than the original next generation matrix. The expression of the reproduction number may have a wide range of applications to many vector-borne diseases. Reproduction numbers can vary from below one to above one or from above one to below one by changing movement rates in different scenarios. The observations provide guidelines on executing movement bans in case of an epidemic. To compute the extinction threshold, corresponding Markov chain process is approximated near disease free equilibrium. The extinction threshold for Continuous-time Markov chain model was analytically connected to the reproduction number under some assumptions. Numerical simulation results agree with analytical results without assumptions, proposing a mathematical problem of proving the existence of the relationships in general. The distance of the extinction threshold were shown to be closer to one than the reproduction number. Consistent trends of probability of extinction varying with disease parameters observed through numerical simulations provide novel insights into disease mitigation, control, and elimination.
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Kumsa, Bersissa. "Molecular investigation of arthropods and vector-borne bacteria from Ethiopia." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM5054/document.
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En outre, nous avons fait une expérience sur les nouveaux outils pour identifier les tiques par MALDI-TOF MS protéines profilage et des méthodes moléculaires. Notre étude visant à explorer les bactéries dans les ixodidae prélevés sur des animaux domestiques en Éthiopie a révélé une prévalence globale de 6% (46/767) des rickettsies de SFG, 3,8% (29/767) ADN de Borrelia et 6,4% (54/842) de C. burnetii dans différentes espèces de tiques. L'étude pour étudier les bactéries dans 303 puces prélevés sur des chiens et des chats domestiques en Ethiopie qui ont été identifiés comme étant morphologiquement Ctenocephalides felis felis, Ctenocephalides canis, Pulex irritans et Echidnophaga gallinacé montré Rickettsia felis dans 21% des puces, principalement dans Ctenocephalides felis, avec un semblable prévalence dans les puces de chiens et de chats. La présence d'Acinetobacter spp. dans M. ovinus, Heterodoxus spiniger, Bovicola ovis et Linognathus vituli. La séquence du gène rpoB partiel a révélé la présence de A. soli, A. lowffii, A. Pitti et 3 nouveaux Acinetobacter spp. dans les poux et Keds. Bartonella melophagi a été identifié par une PCR standard, suivi par un séquençage du fragment de la gltA et gène rpoB chez M. ovinus. Dans l'ensemble, nos résultats alerte les médecins en charge des patients avec fièvre d'étiologie inconnue en Ethiopie et ceux qui se soucient de voyageurs en provenance de l'Ethiopie à prendre en compte la présence de plusieurs espèces zoonotiques à transmission vectorielle de bactéries, y compris SFG rickettsies, C. burnetii, R. felis, B. henselae et B. melophagi comme agents pathogènes potentielsOur study to explore bacteria in ixodid ticks collected from domestic animals in Ethiopia revealed an overall prevalence of 6% (46/767) SFG rickettsiae, 3.8% (29/767) Borrelia DNA and 6.4% (54/842) C. burnetii in different tick species. The study to investigate bacteria in 303 fleas collected from domestic dogs and cats in Ethiopia that were morphologically identified as Ctenocephalides felis felis, Ctenocephalides canis, Pulex irritans and Echidnophaga gallinacean showed Rickettsia felis in 21% of fleas, mainly in Ctenocephalides felis, with a similar prevalence in fleas from dogs and cats. The study to investigate bacteria in lice and sheep ked (Melophagus ovinus) revealed Acinetobacter spp. in M. ovinus, Heterodoxus spiniger, Bovicola ovis and Linognathus vituli. Partial rpoB gene sequence revealed A. soli, A. lowffii, A. pitti and 3 new Acinetobacter spp. in the lice and keds. Molecular identification of lice using an 18S rRNA gene analysis confirmed the morphological methods of lice identification. Bartonella melophagi was identified by standard PCR followed by sequencing of fragments of the gltA and rpoB genes in M. ovinus.Overall, our findings alert physicians managing patients with fever of unknown aetiology in Ethiopia and those who care for travellers from Ethiopia to consider the presence of several vector-borne zoonotic species of bacteria including SFG rickettsiae, C. burnetii, R. felis, B. henselae and B. melophagi as potential causative agents
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Twiddy, Sally Susanna. "The molecular epidemiology and evolution of dengue virus." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269490.
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Rasgon, Jason Laurence. "Wolbachia infection dynamics and applied vector-borne disease control in mosquitoes /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
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Phillips, Victoria. "Tick species and tick-borne disease surveillance in southern Illinois." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2806.
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Human alteration of the landscape and environment is favoring the expansion of ticks and the pathogens they vector throughout the United States. The changes in these distributions are documented through literature and the deposition of specimens in scientific collections. In southern Illinois, tick species records are sporadic and inconsistent with what is actually found in the region. This information is necessary for public health officials to develop prevention strategies against tick-borne illnesses. I conducted research from 2018-2020 to accomplish the following: (1) conduct a ticks species and tick-borne disease survey of southern Illinois, (2) create habitat maps for Amblyomma americanum and Dermacentor variabilis in the region, and (3) attempt to identify microhabitat variables influencing tick abundance. To accomplish my first objective, I sampled 26 sites from 11 counties in southern Illinois utilizing the tick drag method. Ticks were then tested for their associated pathogens using quantitative PCR. Four species of tick, Amblyomma americanum (the lone star tick), Dermacentor variabilis (the American dog tick), Ixodes scapularis (the black-legged deer tick), and Amblyomma maculatum (the Gulf Coast tick) were identified. Rickettsia rickettsii and Rickettsia parkeri causative agents of human rickettsiosis, Ehrilichia ewingii and Ehrlichia chaffeensis, causative agents of human granulocytic ehrlichiosis, and Rickettsia amblyommii whose effects are not known, were all found in the study region. The second objective, lone star and American dog tick species distribution models (SDMs), was accomplished using the popular SDM program, Maxent. Maxent uses species presence data and their associated environmental characteristics to create predictions of habitat suitability. The resulting models indicate a correlation for both species with the Shawnee National Forest, likely due to the fragmented habitat structure as indicated by the strong impact of cultivated and managed vegetation on both species models. Lastly, I attempted to identify microhabitat characteristics that influence tick species abundance. Temperature, humidity, canopy closure, and wind speed were measured and recorded and vegetation density estimates and soil moisture were recorded categorically at each site, each visit. Using a chi-squared test I proved that tick abundance is not static, and varies throughout the summer months. I then used a principal component analysis (PCA) to assess correlation between habitat variables and tick abundance, but no signal was detected. This study established a baseline for tick species and tick-borne disease presence in southern Illinois. The information resulting from this study can be used to inform public health officials and inform future tick-borne disease prevention strategies. I recommend continued surveillance of the area to monitor species distributions and resulting pathogen risk to residents.
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Alonso, Wladimir Jimenez. "Vector host choice and the environmental context of mosquito-borne virus transmission." Thesis, University of Oxford, 2003. http://ora.ox.ac.uk/objects/uuid:bc3632b8-321a-4751-8797-80b40098ec27.
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The present thesis explored ethological and geographical approaches for the investigation of vector-borne parasites. In the first part, the role of associative learning on vector preferences for hosts was investigated through a comprehensive series of behavioural experiments using the vector of dengue and yellow fever diseases, the mosquito Aedes aegypti. To this end, the possibility that the mosquitoes were able to associate unconditional stimuli with particular odours and visual patterns to which they were responsive was explored, but no evidence supporting the hypothesis that associative learning abilities are present in adults of this species was found. A critical review of the literature on learning in mosquitoes conducted afterward allowed the reinterpretation of findings in the field, narrowing the scope of evidence suggesting the existence of these cognitive abilities in some species. In the second part of the thesis, the distribution and evolution of mosquito-borne viruses was investigated with the use of geo-coded environmental data and spatial statistics. Initially, the eco-climates associated with the distribution of Japanese encephalitis virus were described and modelled, allowing the production of a worldwide predictive map defining the probability of each region to develop this disease in the future. Predominating amongst those areas shown to be under high risk were the equatorial regions of South America and Africa. The methodology used to infer such patterns – non-linear discriminant analysis – was subsequently explored with a number of simulations. Overall, differences in the choice of parameters required for the analysis were shown to lead to differences in the final outputs produced, basically in those cases where the environmental range for which predictions are generated is not rigorously limited. Finally, eco-climate surrogates for the evolution of the Japanese encephalitis serocomplex were investigated, but the current environmental distances between the viruses did not seem to be associated with the events leading to their speciation.
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Shukullari, Enstela [Verfasser]. "Parasites and Vector-borne Diseases in Client-owned Dogs in Albania / Enstela Shukullari." München : Verlag Dr. Hut, 2016. http://d-nb.info/1135988994/34.
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Cambon, Marine. "Heterogeneity within infections : the case of the vector-borne insect pathogen, Xenorhabdus nematophila." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30308.
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De nombreuses études ont jusqu'ici considéré les infections comme étant des interactions deux-à-deux, entre un hôte et un pathogène, minimisant ainsi la complexité du processus infectieux. En effet, les infections sont souvent très hétérogènes, menant à des interactions plus complexes. Au cours de ce travail, nous cherchons à répondre à deux questions: (i) La transmission d'un pathogène peut-elle être impactée lorsque de l'hétérogénéité phénotypique apparaît dans sa population au cours de l'infection ? (ii) Comment les pathogènes interagissent-ils avec la communauté bactérienne généralement associée à l'hôte avant l'infection ? Pour étudier ces questions, nous nous sommes intéressés à Xenorhabdus nematophila, une bactérie pathogène d'insectes transmise par un vecteur, le némaotde Steinernema carpocapsae. Au cours d'une infection par X. nematophila, différentes sous-populations ayant différentes caractéristiques phénotypiques sont produites. Nous avons cherché à déterminer les mécanismes moléculaires responsables de cette diversification phénotypique, ainsi que sa potentielle valeur adaptative pour X. nematophila. Nous avons montré que certaines de ces formes phénotypique sont des mutants qui semblent être sous forte sélection positive au cours de l'infection. À l'inverse, ces mutants ont un impact négatif sur la reproduction du vecteur nématode, ce qui réduit leur transmission. La dynamique d'hétérogénéité phénotypique chez X. nematophila semble donc déterminée par des pressions de sélections contraires à court terme et à long terme. La production de molécules anti-microbiennes chez X. nematophila devraient lui permettre de dominer la communauté bactérienne à l'intérieur de l'insecte et faciliter sa ré-association avec son vecteur. Nous avons donc décrit la composition de la communauté microbienne présente dans des insectes morts d'une infection par X. nematophila, et montré qu'en dépit de sa production d'antibiotiques, X. nematophila est loin de dominer la communauté microbienne après la mort de l'insecte. Elle cohabite avec des bactéries provenant à la fois du microbiote de l'hôte insecte, et de celui du vecteur nématode. Cela soulève de nombreuses questions sur le rôle d'autres microorganismes dans les interactions Xenorhabdus-Steinernema, et sur leur influence dans l'évolution de cette symbiose mututalisteNumerous studies have considered infections as pairwise interactions between a single pathogen and its host, sometimes leading to an incomplete picture of infectious processes. In this work, we focused on more complex types of interactions that arise because infections are usually heterogeneous. More precisely, we have investigated two main issues: (I) how pathogen transmission is impacted by phenotypic heterogeneity which arises within the pathogen population during the infection, and (ii) how do pathogens interact with the bacterial community which is naturally associated to the host before infection? To assess these questions, we have been studying Xenorhabdus nematophila, an insect-killing bacterial pathogen which is transmitted by a nematode vector, Steinernema carpocapsae. One interesting feature of X. nematophila is that it produces different sub-populations during the course of an infection, each one having distinctive phenotypic features (e.g. one form produces antibiotics and is mobile, while the other does not produce antibiotics nor flagella). In this work, we first tried to identify the molecular mechanisms responsible for this diversification of phenotypes, and tested if phenotypic heterogeneity in X. nematophila has some adaptive value. We showed that some of these phenotypic forms were mutants, which seem to be under strong positive selection during infection. We also showed, however, that these mutants impair nematodes reproduction, which in turn reduces transmission. Therefore, the dynamics of phenotypic heterogeneity in X. nematophila seems to be determined by contradictory short-term and long-term selective pressures. A second interesting feature of X. nematophila is that it produces a lot of antimicrobial compounds which should allow it to dominate the bacterial community inside the insect it has killed. This can be key to ensure the re-association of X. nematophila with its nematode vector inside the insect cadaver. We investigated the bacterial composition of the microbial communities present in insects cadavers after infection by X. nematophila. We found that despite the numerous antibiotics it is able to secrete, X. nematophila is far from dominating microbial community after host death. It rather cohabits with microorganisms from the microbiota of both the insect host and the nematode vector. This raises numerous questions about the impact of these other microorganisms on Xenorhabdus-Steinernema interactions, and therefore on their potential influence on how this mutualistic association has evolved
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Keller, Judith Ina. "Protein Mass Spectrometry Aids In Chagas Vector Blood Meal Identification And Offers An Innovative Approach To Battling Vector-Borne Diseases." ScholarWorks @ UVM, 2019. https://scholarworks.uvm.edu/graddis/994.
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Vector borne-diseases make up a significant portion of morbidity and mortality worldwide, being responsible for around 700,000 deaths annually according to the World Health Organization. Neglected, tropical diseases such as Chagas disease have a significant impact on people in Latin America, affecting millions, and especially those residing in rural areas. Chagas disease is the number one cause for heart disease in Latin America, and is caused by the Trypanosoma cruzi parasite, carried by Triatominae insect vectors. The intricate life cycle of the parasite, ecology and behavior of the vector, and lack of disease treatment options, make Chagas disease challenging to control. Prevention measures are highly sought after, and implementation science approaches such as Ecohealth management engage affected communities in disease prevention. Knowing what insect vectors are feeding on sheds light on vector ecology and behavior, aiding in vector management which is pivotal in disease prevention.
While DNA-based methods have traditionally been used to study vector blood meals, they come with limitations and challenges, such as the need for fresh, high abundance blood meals. Therefore, the goal of this research was to evaluate Chagas vector blood meal sources using an innovative protein mass spectrometry-based approach. We demonstrate first the ability to utilize liquid chromatography tandem mass spectrometry (LC-MS/MS) to correctly identify hemoglobin protein peptides from mouse blood and subsequently identify Chagas vector blood meal sources from field-collected insect vectors where blood meal identification is compared with traditional DNA-based methods as a control.
An experimental feeding study allowed us to then demonstrate the longevity of hemoglobin protein peptides for blood meal detection, showing LC-MS/MS-based blood meal identification outperforms DNA-based polymerase chain reaction (PCR) at least 4 weeks post-feeding and 12 weeks post-molting. This allowed us to test the limits of our innovative detection method experimentally and comparatively.
Finally, we evaluated blood meals in field-caught insect vectors collected as part of a large collaborative Ecohealth project in Central America. LC-MS/MS identified two times as many blood meals in insect vectors, including those that did not have blood meals detected with DNA-based PCR. As single vectors often feed on multiple sources, we also validated our ability to decipher multiple blood meals from an individual vector and showed the ability to quantify a blood meal using synthetic AQUA (Absolute QUAntification) peptides, a first step in using quantification data for identifying blood meals not currently in our underlying database. Furthermore, we show that lower resolution mass spectrometers are able to identify blood meals from taxa correctly, an important and strong attribute of our LC-MS/MS-based method, opening the door to using proteomics in countries where Chagas disease is endemic and resources are limited.
Even though expertise and resources of research labs differ in locations across the globe, herein is described how LC-MS/MS is a valuable additional tool for fighting neglected tropical diseases. Ultimately, hemoglobin-based LC-MS/MS vector blood meal identification is a complementary technique to available molecular methods and can confidently identify Chagas vector blood meal sources to aid in understanding vector biology and ecology, and aid in developing appropriate Ecohealth vector control measures.
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Peery, Ashley Nicole. "Chromosomal Evolution of Malaria Vectors." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/71698.
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International malaria control initiatives such as the Roll Back Malaria Initiative (RBM) and the Medicines for Malaria Venture (MMV) mobilize resources and spur research aimed at vector control as well as the treatment and eventual eradication of the disease. These efforts have managed to reduce incidence of malaria by an estimated 37% worldwide since 2000. However, despite the promising success of control efforts such as these, the World Health Organization reports a staggering 438,000 deaths from malaria in 2015. The continuing high death toll of malaria as well as emerging insecticide and antimalarial drug resistance suggests that while encouraging, success in reducing malaria incidence may be tenuous. Current vector control strategies are often complicated by ecological and behavioral heterogeneity of vector mosquito populations. As an additional obstruction, mosquito genomes are highly plastic as evidenced by the wealth or chromosomal inversions that have occurred in this genus. Chromosomal inversions have been correlated with differences in adaptation to aridity, insecticide resistance, and differences in resting behavior. However, a good understanding of the molecular mechanisms for inversion generation is still lacking. One possible contributor to inversion formation in Anopheles mosquitoes includes repetitive DNA such as transposable elements (TEs), tandem repeats (TRs) and inverted repeats (IRs). This dissertation provides physical maps for two important malaria vectors, An. stephensi and An. albimanus (Ch.2 and Ch. 3) and then applies those maps to the identification of inversion breakpoints in malaria mosquitoes. Repeat content of each chromosomal arm and the molecular characterization of lineage specific breakpoints is also investigated (Ch. 2 and Ch.4). Our study reveals differences in patterns of chromosomal evolution of Anopheles mosquitoes vs. Drosophila. First, mosquito chromosomes tend to shuffle as intact elements via whole arm translocations and do not under fissions or fusions as seen in fruitflies. Second, the mosquito sex chromosome is changing at a much higher rate relative to the autosomes in malaria mosquitoes than in fruit flies. Third, our molecular characterization of inversion breakpoints indicates that TEs and TRs may participate in inversion genesis in an arm specific manner.Ph. D.
Malaria is a complex and devastating disease vectored by the bite of a female Anopheles mosquito. This disease claimed an estimated 438,000 lives in 2015. The mobilization of funding and resources as part of global malaria eradication initiatives have reduced the global incidence of malaria by 37% in the last 15 years. Deaths from malaria are also 60% lower vs. the year 2000. These promising gains are threatened by the ability of Anopheles mosquitoes to adapt in the face of malaria control efforts. Anopheles mosquito chromosomes are known to be highly plastic, as evidenced by numerous chromosomal inversions. Recent years have seen increases in insecticide resistance, and behavioral change in mosquito populations that allow them to avoid insecticides and remain prolific vectors of disease. This ability of mosquito vectors to adapt threatens to unravel recent progress towards a malaria free world. The projects presented in this dissertation explore mechanisms of chromosomal evolution, specifically the potential role of repetitive DNA in the generation of chromosomal inversions. The exploration of chromosomal inversions was facilitated by the creation of physical maps for Anopheles species. Prominent malaria vectors An. stephensi andAn. albimanus were physically mapped in Chapter 2 and Chapter 3 respectively. In chapter 1 and chapter 3 physical maps are utilized for the identification of chromosomal inversion breakpoints using 2 species (Ch. 2) and many species (Ch. 4). Repeat content was quantified along each chromosomal arm (Ch 2,4) and in inversion breakpoint regions (Ch 3). This dissertation presents physical maps for two important malaria species that have been applied to the study of chromosomal evolution and will also serve as community tools for further study of malaria mosquitoes. Our work on chromosomal evolution has revealed the Anopheles chromosomes tend to undergo translocations as intact elements and do not under fissions and fusions as seen in fruitflies. We also find that the malaria mosquito sex chromosome changes much more rapidly relative to the autosomes than in fruitflies. Additionally, repetitive DNA including transposable elements (TEs) and tandem repeats (TRs) may be encouraging chromosomal inversions but with differing roles on different chromosomal arms.
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Frank, Anna Carolin. "Lifestyle and Genome Evolution in Vector-Borne Bacteria : A Comparison of Three Bartonella Species." Doctoral thesis, Uppsala universitet, Molekylär evolution, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5913.
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Bacterial genomes provide records of the molecular processes associated with emergence and evolution of different bacterial lifestyles. This thesis is based on whole-genome comparisons within the genus Bartonella, an excellent model system for studies of host- and vector-specificity and infection outcome in animal-associated bacteria. The louse-borne human specialist and trench fever agent Bartonella quintana was contrasted to the flea-borne generalist relatives Bartonella henselae and Bartonella grahamii, which cause asymptomatic infection in cat and mouse respectively. While B. henselae is commonly isolated from humans, and causes cat scratch disease, there is only one reported case of B. grahamii human infection. The gene complements of the three species are nested like Russian dolls with the smaller genome (B. quintana) being entirely contained in the medium sized (B. henselae), which in turned is contained in the largest (B. grahamii). Size differences reflect differences in the horizontally and vertically acquired gene content, and in the number of genus- and species- specific genes, owing to differential impact of bacteriophages and plasmids, and to different degrees of genome decay. These processes can be attributed to the three distinct lifestyles. Comparisons with other alpha-proteobacteria suggest that the Bartonella genus as a whole evolved from plant-associated species, and that horizontal transfer, in particular of genes involved in interaction with the host, played a key role in the transition to animal intracellular lifestyle. The long-term genome decay associated with this lifestyle is most advanced in the host-restricted B. quintana. The broad host-range species B. grahamii has the largest genome and the largest proportion of auxiliary DNA of the three, probably because it has access to a larger gene pool. In encodes all the known pathogenicity determinants found in the genomes of B. henselae and B. quintana, suggesting that these genes primarily evolved to facilitate colonization in the reservoir host.
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Auty, Harriet K. "Ecology of a vector-borne zoonosis in a complex ecosystem : trypanosomiasis in Serengeti, Tanzania." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/4223.
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Unravelling the complexities of a disease with multiple wildlife host and multiple tsetse vector species is no easy task. After over a century of field observations, experimental studies, anecdotal evidence and conjecture, the role of wildlife in the transmission of trypanosomes is still unclear. Recently, however, frameworks used in the studies of other vector-borne diseases with wildlife reservoirs showed that not only is it possible to understand transmission, but that spatio-temporal predictions of human disease risk and targeted control are realistic aims, even in such complex systems. This thesis explores the epidemiology of human African trypanosomiasis (HAT) in the Serengeti-Mara ecosystem in Northern Tanzania, where recent cases in tourists have highlighted the disease as a public health and economic concern. Assessment of the prevalence of trypanosome infections in different wildlife species is the first step in investigating the relative importance of different species in disease transmission. Identification of trypanosomes relies on sensitive and specific diagnostic tests. Polymerase chain reaction (PCR) protocols based on interspecies differences in the length of the ribosomal internal transcribed spacer (ITS) regions have been widely used in livestock to identify multiple trypanosome species in one PCR reaction. This study represents the first assessment of these protocols on blood samples collected from wildlife. Clonal sequence analysis of PCR products revealed a large range of trypanosomes circulating in wildlife, including Trypanosoma congolense, Trypanosoma brucei, Trypanosoma simiae Tsavo, Trypanosoma godfreyi and Trypanosoma vivax. In addition sequences similar to known sequences, termed Trypanosoma simiae-like and T. vivax-like trypanosomes, may reflect further diversity. However, further characterisation is needed before ITS protocols can be used widely for epidemiological studies in wildlife. The prevalence of T. brucei s.l. and T. congolense varied widely between species. This variation was predominantly explained by taxonomic classification, suggesting intrinsic differences in response to trypanosomes. Trypanosoma brucei rhodesiense, the subspecies responsible for HAT, was identified in lion, hyaena and reedbuck. Age significantly affected the prevalence of T. congolense in lion and hyaena, with the highest prevalence in subadults. The lack of statistically significant differences in prevalence between animals sampled live or after death confirmed that post-mortem sampling provides a method for increasing sample sizes in wildlife studies. The complex relationship between tsetse density and prevalence of trypanosome infections illustrated the difficulties of assessing data from diverse ecosystems with many potential confounding factors. A cross-sectional study of Glossina swynnertoni and Glossina pallidipes, the main tsetse species in Serengeti, highlighted the difficulties of integrating the results of microscopy and PCR to generate meaningful measures of the prevalence of transmissible T. brucei infections for epidemiological studies. However, PCR results suggested that G. pallidipes may be more important as a vector of T. brucei s.l. than has been previously recognised. Spatial variation in both tsetse density and the prevalence of trypanosome infections suggests human disease risk is heterogeneous. The results of this study, along with relevant literature, are considered within the context of frameworks used for other vector-borne diseases and the implications for disease management discussed.
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Kisinza, William Nhandi. "Natural history of Ornithodoros & vector control of tick-borne relapsing fever in Tanzania." Thesis, University of Liverpool, 2006. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431724.
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Tangena, Julie-Anne Akiko. "The risk of vector-borne disease exposure in rubber plantations of northern Lao PDR." Thesis, Durham University, 2016. http://etheses.dur.ac.uk/11981/.
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Unprecedented economic growth in South-East Asia has encouraged the expansion of rubber plantations. Outbreaks of vector-borne diseases occur in these plantations, yet data on the vector dynamics is limited. In this thesis I describe the mosquito ecology in rubber plantations compared to neighbouring habitats in northern Lao PDR, to assess the risk of vector-borne diseases for rubber workers and villagers, and to identify how to mitigate these risks. I carried out a study to identify an ethically sound alternatives to human landing catches (HLC). The human-baited Double Net trap (HDN) collected similar numbers of Anopheles and Culex as HLC, but under-estimated the number of Aedes albopictus. As both HLC and HDN are crude ways of identifying the human-biting rate, the HDN is a representative method to estimate the human-biting rate outdoors without exposing collectors to mosquito bites. Using the HDN, I compared the adult mosquito dynamics in the secondary forests, immature rubber plantations, mature rubber plantations and villages. A total of 113 species were identified, including 61 species not documented in Lao PDR before The highest number of mosquitoes were collected in the secondary forests. Three of the four most common species found were vector species; the dengue and chikungunya vector Ae. albopictus, the lymphatic filariasis vector Ar. kesseli and the JE vector Cx. vishnui. Additionally, in all habitats a daily exposure to malaria vectors was found. To assess the risk of exposure to vector-borne diseases I explored the local human behaviour using sociological methods. Compared to staying in the village, dengue exposure risk increased when working in the plantations, which was exasperated when also living in these man-made forests. By contrast, malaria vector exposure risk decreased when living in the plantations. I identified the characteristics of mosquito breeding sites in rubber plantations and villages. Aedes albopictus immature stages were most frequently collected from tyres and latex collection cups in the mature rubber plantations and from tyres and water containers (< and > 10 L) in the villages. A majority of the Cx. quinquefasciatus were collected from water containers (< and > 10 L) in the mature rubber plantations and villages. Anopheles dirus s.l. were mostly collected from puddles in the immature rubber plantations and villages. This thesis emphasizes the importance of implementing mosquito control in the rubber plantations for the control of dengue disease. Larval control and personal protection methods are possible vector control methods for our study area. The successful implementation of vector control requires an inter-sectoral approach, with strong collaboration between the health sector, rubber industry and local communities.
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Chapman, Gail Elaine. "Mosquito-borne arboviruses of horses : vector presence, competence and disease prevention in the UK." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3022449/.
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Mosquito-borne arboviruses cause significant morbidity and mortality in horses worldwide and can have substantial welfare and economic ramifications. Eight main arboviruses of equids are discussed in this thesis: the flaviviruses West Nile Virus (WNV), Japanese encephalitis virus (JEV), Murray Valley encephalitis virus (MVEV), and the alphaviruses Eastern equine encephalitis, Western equine encephalitis virus (WEEV), Venezuelan equine encephalitis virus (VEEV), Ross River virus (RRV), and Getah virus (GETV). Except for Getah virus, these viruses cause disease in humans as well as equids. To investigate the risk to horses in the UK, work included in this thesis comprised investigation of mosquito species presence on equine premises, and assessment of vector competence for equine arboviruses. Strategies for protection of horses from mosquito-biting were investigated, and the knowledge of horse owners with regards to equine arboviral diseases, vectors and control and prevention was explored, as this knowledge is important in disease preparedness, surveillance and control. Known and potential vectors of equine arboviruses are present on equine premises across England. The most widespread was found to be Culiseta annulata, which was also demonstrated to be a competent laboratory vector for JEV and has been shown previously to be competent for WNV. The most abundant species trapped was Ochlerotatus detritus, which has been previously shown to be a competent vector for some flaviviruses (JEV, WNV) and was demonstrated here to be laboratory competent for RRV. Container habitats of Culex pipiens were commonly found on equine premises and this species was shown here to transmit JEV at high rates at 18°C, which represents average temperatures which may be experienced in a warm summer period in the south of England. Both Cs. annulata and Oc. detritus were only inefficient laboratory vectors of epizootic VEEV. Apparent virus clearance and nonlinear temperature-transmission relationships were demonstrated for several virus-vector pairs studied. Horse-owner knowledge of equine arboviral disease was shown to be limited. Spray repellents were shown to have some benefit in the protection of individual horses from mosquito biting, and the potential for some degree of utility in reducing the risk of infection by arboviruses, under low to moderate infection pressure, and in situations in which there is no vaccine available.
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Thomas, Stephanie Verfasser], and Carl [Akademischer Betreuer] [Beierkuhnlein. "Vector-borne Disease Risk Assessment in Times of Climate Change: The Ecology of Vectors and Pathogens / Stephanie Thomas. Betreuer: Carl Beierkuhnlein." Bayreuth : Universität Bayreuth, 2014. http://d-nb.info/1063995566/34.
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Thomas, Stephanie [Verfasser], and Carl [Akademischer Betreuer] Beierkuhnlein. "Vector-borne Disease Risk Assessment in Times of Climate Change: The Ecology of Vectors and Pathogens / Stephanie Thomas. Betreuer: Carl Beierkuhnlein." Bayreuth : Universität Bayreuth, 2014. http://d-nb.info/1063995566/34.
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Retief, Liezl. "Molecular detection and characterisation of potentially zoonotic bacteria in bathyergids from the Western Cape Province." Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/67139.
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Globally emphasis has been given to identify emerging and re-emerging pathogens. Rapid urban
expansion creates a problem which is two-fold. Firstly, increasing slum living conditions due to
inadequate rate of infrastructure development results in an increased reliance on natural resources,
including the capture and consumption of surrounding wildlife to subsist, thereby facilitating the transfer
of emergent zoonotic pathogens. Secondly, through activities such as pollution or alien species
introductions, the rapid transformation of once pristine environments, alters natural systems, potentially
exposing these environments to new bacterial pathogens. Therefore, the main aim of this study was to
assess overlooked bacterial species harboured by four host species (Bathyergus suillus, Georychus
capensis, Cryptomys hottentotus hottentotus and Fukomys damarensis) belonging to the subterranean
rodent family Bathyergidae, which inhabit an environment well-suited for an array of bacterial species,
and which varied in their exposure to human settlements. Bacterial prevalence and diversity was initially
evaluated using broad-range PCR techniques in combination with nucleotide sequencing. This revealed
high levels of bacterial prevalence (82.91%) and mixed infections (22.60%) in bathyergid species. Two
bacterial groups, the Bacillus cereus complex (a group of soil-dwelling bacterial strains with pathogenic
potential with an overall prevalence of 8.55%) and haemotropic Mycoplasma strains (vector-borne
bacterial strains of zoonotic potential with an overall prevalence of 1.28%) were subsequently selected for
further genetic analysis with genus and species-specific PCRs. Bacillus molecular screening and
phylogenetic analyses was achieved by targeting four gene regions with seven published primer assays
and two novel PCR assays. This enabled identification of two B. cereus complex strains in bathyergid
lungs and revealed an overall B. cereus complex prevalence of 17.95% for the 234 bathyergid lung
samples screened. Bacillus genome prevalence was significantly higher in B. suillus individuals (45.35%),
sampled in a peri-urban environment, compared to the other bathyergid species sampled from pristine
habitats (ranging from 0% - 4.44%). Anthropogenic activities in the area where B. suillus was sampled
could, at least partially, attribute to the perceived difference between urban and naturally sampled
bathyergid species, highlighting the role of B. suillus to act as both a reservoir of potentially zoonotic
pathogens and as a sentinel for anthropogenic soiling. Mycoplasma molecular screening using three
different PCR assays, all targeting the 16S rRNA gene region, confirmed an overall haemotropic
Mycoplasma prevalence of 24.13% in the 286 bathyergid organs (lung, spleen and liver) screened. A
significantly higher prevalence and diversity of haemotropic Mycoplasma strains was found in B. suillus
lungs (41.86%) compared to its naturally occurring relatives (ranging from 0%-36%). Phylogenetic analyses identified six novel haemotropic Mycoplasma strains, all grouping within a discrete
monophyletic cluster, sister to Mycoplasma coccoides, and comprising two well-supported sub-clusters.
The human introduction of commensal rodents harbouring Mycoplasma strains transferred through
cosmopolitan arthropod vectors to indigenous bathyergids, likely underlies the higher prevalence in urban
areas, although other biotic and abiotic factors affecting ectoparasite load also merit consideration. The
data generated by the current study indicate the need to identify largely overlooked and potentially
zoonotic bacterial pathogens in subterranean mammals and emphasises the importance of monitoring
anthropogenically-introduced, opportunistic pathogens and the threats they pose to vulnerable
communities and co-occurring, free-living animal speciesDissertation (MSc)--University of Pretoria, 2017.
Airports Company of South Africa (ACSA)
National Research Foundation (NRF)
Zoology and Entomology
MSc
Unrestricted
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Millins, Caroline Louise. "Ecological drivers of a vector borne pathogen : distribution and abundance of Borrelia burgdorferi sensu lato and its vector Ixodes ricinus in Scotland." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7311/.
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Vector-borne disease emergence in recent decades has been associated with different environmental drivers including changes in habitat, hosts and climate. Lyme borreliosis is among the most important vector-borne diseases in the Northern hemisphere and is an emerging disease in Scotland. Transmitted by Ixodid tick vectors between large numbers of wild vertebrate host species, Lyme borreliosis is caused by bacteria from the Borrelia burgdorferi sensu lato species group. Ecological studies can inform how environmental factors such as host abundance and community composition, habitat and landscape heterogeneity contribute to spatial and temporal variation in risk from B. burgdorferi s.l. In this thesis a range of approaches were used to investigate the effects of vertebrate host communities and individual host species as drivers of B. burgdorferi s.l. dynamics and its tick vector Ixodes ricinus. Host species differ in reservoir competence for B. burgdorferi s.l. and as hosts for ticks. Deer are incompetent transmission hosts for B. burgdorferi s.l. but are significant hosts of all life-stages of I. ricinus. Rodents and birds are important transmission hosts of B. burgdorferi s.l. and common hosts of immature life-stages of I. ricinus. In this thesis, surveys of woodland sites revealed variable effects of deer density on B. burgdorferi prevalence, from no effect (Chapter 2) to a possible ‘dilution’ effect resulting in lower prevalence at higher deer densities (Chapter 3). An invasive species in Scotland, the grey squirrel (Sciurus carolinensis), was found to host diverse genotypes of B. burgdorferi s.l. and may act as a spill-over host for strains maintained by native host species (Chapter 4). Habitat fragmentation may alter the dynamics of B. burgdorferi s.l. via effects on the host community and host movements. In this thesis, there was lack of persistence of the rodent associated genospecies of B. burgdorferi s.l. within a naturally fragmented landscape (Chapter 3). Rodent host biology, particularly population cycles and dispersal ability are likely to affect pathogen persistence and recolonization in fragmented habitats. Heterogeneity in disease dynamics can occur spatially and temporally due to differences in the host community, habitat and climatic factors. Higher numbers of I. ricinus nymphs, and a higher probability of detecting a nymph infected with B. burgdorferi s.l., were found in areas with warmer climates estimated by growing degree days (Chapter 2). The ground vegetation type associated with the highest number of I. ricinus nymphs varied between studies in this thesis (Chapter 2 & 3) and does not appear to be a reliable predictor across large areas. B. burgdorferi s.l. prevalence and genospecies composition was highly variable for the same sites sampled in subsequent years (Chapter 2). This suggests that dynamic variables such as reservoir host densities and deer should be measured as well as more static habitat and climatic factors to understand the drivers of B. burgdorferi s.l. infection in ticks. Heterogeneity in parasite loads amongst hosts is a common finding which has implications for disease ecology and management. Using a 17-year data set for tick infestations in a wild bird community in Scotland, different effects of age and sex on tick burdens were found among four species of passerine bird (Chapter 5). There were also different rates of decline in tick burdens among bird species in response to a long term decrease in questing tick pressure over the study. Species specific patterns may be driven by differences in behaviour and immunity and highlight the importance of comparative approaches. Combining whole genome sequencing (WGS) and population genetics approaches offers a novel approach to identify ecological drivers of pathogen populations. An initial analysis of WGS from B. burgdorferi s.s. isolates sampled 16 years apart suggests that there is a signal of measurable evolution (Chapter 6). This suggests demographic analyses may be applied to understand ecological and evolutionary processes of these bacteria. This work shows how host communities, habitat and climatic factors can affect the local transmission dynamics of B. burgdorferi s.l. and the potential risk of infection to humans. Spatial and temporal heterogeneity in pathogen dynamics poses challenges for the prediction of risk. New tools such as WGS of the pathogen (Chapter 6) and blood meal analysis techniques will add power to future studies on the ecology and evolution of B. burgdorferi s.l.
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Vu, Hai Vinh. "Salivary antigenic proteins from Ixodidae and Anopheles : a novel tool for vector-borne diseases monitoring." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM5052/document.
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Les MVs sont un problème majeur de santé publique. L'émergence des MVs nécessite de nouveaux outils pour la surveillance de ces maladies. Ce projet s’intéresse aux deux familles de vecteurs: Ixodidae (R. sanguineus, D. reticulatus et I. ricinus) et Anophèles (An. gambiae s.l. et An. funestus). Une revue synthétise les données actuelles des MTTs et leur vectors, avant de présenter des méthodes de surveillance de ces maladies. La partie expérimentale s'est concentré sur l'élaboration de méthodes pour la sélection des utiles protéines salivaires pour l'évaluation du contact hôte-vecteur. Pour Ixodidae, la stratégie antigénique utilisée a permis d’identifier des protéines salivaires antigéniques communes et spécifiques d’espèce de ces tiques. Ces protéines pourraient servir pour l’évaluation de l’exposition de l’hôte aux Ixodidae. Pour Anophèles, la stratégie candidate utilisée a révélé une protéine salivaire antigénique d’Anopheles (f-5’nuc) pouvant être marqueur prometteur distinguant l'exposition aux Anophèles au niveau de l'espèce. Pour conforter ces résultats, l’établissement d’une relation entre la cinétique des réponses d'anticorps de l’hôte contre ces candidats salivaires, la faune Culicidienne et la variation de densité des populations de moustiques est en cours. Ce projet a souligné que tous les deux vectors peuvent induire une réponse immunitaire chez leur hôte contre des protéines salivaires antigéniques injectées. Il a permis également d’identifier des protéines salivaires permettant la discrimination de l'exposition d'hôte aux vecteurs au niveau du genre ou de l’espèce, offrant de nouvelles stratégies pour la surveillance des MVsVector-borne diseases (VBD) are a major health problem worldwide. The emergence of VBD requires novel monitoring tools. The present project focused on two vector families: Ixodidae (R. sanguineus, D. reticulatus and I. ricinus) and Anopheles (An. gambiae s.l. and An. funestus). A review updates the repartition of TBD, their vectors in Europe, prior to present the different tools for monitoring of TBD transmission. The experimental part focused on establishing methods for selection of useful vector salivary proteins for host-vector contact assessment. Concerning Ixodidae, the studied antigenic strategy successfully identified the shared and discriminant tick salivary antigenic proteins. These identified proteins could be an useful tool to measure host exposition to Ixodidae bites. Concerning Anopheles, the studied candidate strategy revealed an salivary antigenic protein ( f-5’nuc) that could be a promising antigenic marker to distinguish malaria vector exposure at the species level. To comfort these results, the relationship between the kinetic host antibody response against anopheline salivary candidates and the Anopheles fauna population and density variations is under progress. The present work underlined that both two studied vector families following blood meal can elicit a host antibody response against injected vector salivary antigenic proteins. This project proposed for the first time some vector salivary proteins allowing discriminating host exposure to vector bites from genus to species level, opening new strategies for VBD monitoring at the individual and population levels
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Ouma, David Omondi. "Bionomics of vector-borne diseases in sites adjacent to lakes Victoria and Baringo in Kenya." Thesis, University of the Western Cape, 2016. http://hdl.handle.net/11394/5338.
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Philosophiae Doctor - PhDBionomics of vector-borne pathogens (VBPs) is a complex phenomenon that involves understanding the ecology of arthropod borne pathogens and vertebrate hosts potentially involved in their transmission cycles. Investigations into the bionomics of viral and bacterial VBPs circulating in Baringo and Homa Bay Counties of Kenya were carried out. Specifically, vertebrate hosts represented in mosquito bloodmeals, presence of arboviruses in blood fed mosquitoes and patients presenting with acute undiagnosed febrile illnesses in rural health facilities, and tick borne pathogens (TBPs) diversity in ticks of animals were identified. Mosquitoes were trapped by BG sentinel and CDC light traps, while ticks were sampled directly from domestic animals and tortoises close to human habitation along the shores and adjacent islands of Lakes Victoria and Baringo in Kenya. Blood and sera were also sampled from patients presenting with acute febrile illnesses visiting four rural health facilities in Homa Bay County. Mosquitoes and ticks were sorted and identified to species using standard morphological taxonomic keys. All the biological samples (blood-fed mosquitoes, ticks and blood/sera) were processed using molecular and culture procedures for detection of VBPs (arboviruses, Ehrlichia, Anaplasma, Rickettsia and protozoa). Among 445 blood-fed Aedeomyia, Aedes, Anopheles, Culex, Mansonia, and Mimomyia mosquitoes, 33 bloodmeal hosts were identified including humans, eight domestic animal species, six peridomestic animal species and 18 wildlife species. Further detection of Sindbis and Bunyamwera viruses was done on blood-fed mosquito homogenates by Vero cell culture and RTPCR in Culex, Aedeomyia, Anopheles and Mansonia mosquitoes from Baringo that had fed on humans and livestock. In TBPs assay, 585 tick pools were analysed consisting of 4,126 ticks collected in both study areas. More ticks were sampled in Baringo (80.5%), compared to Homa Bay (19.5%). In Baringo, agents of ehrlichiosis were detected from Amblyomma and Rhipicephalus ticks including Ehrlichia ruminantium (12.3%), Ehrichia canis (10.5%) and Paracoccus sp. (4.4%). Agents of anaplasmosis included Anaplasma ovis (7.2%), Anaplasma platys (4.4%) and Anaplasma bovis (4.0%), all from Hyalomma, Amblyomma and Rhipicephalus ticks, as well as agents of rickettsiosis, including Rickettsia africae, Rickettsia aeschlimannii, Rickettsia rhipicephali, Rickettsia montanensis and a Rickettsia sp. that was not conclusively characterized. Babesia caballi, Theileria sp. and Hepatozoon fitzsimonsi were also detected from both Rhipicephalus ticks and Amblyomma ticks. In Homa Bay, Ehrichia ruminantium (17.5%) and Ehrichia canis (9.3%) were isolated from Amblyomma latum and Rhipicephalus pulchellus, as well as Anaplasma platys (14.4%) and Anaplasma ovis (14.4%) from Amblyomma and Rhipicephalus species. In determination of the occurrence of arboviruses among patients presenting with acute febrile illnesses, acute Bunyamwera 3 (0.9%) and Sindbis 2 (0.6%) infections were detected by RT-PCR and cell culture and Sindbis seroprevalence was determined by plaque assay. Though a significant proportion of these patients tested positive for low Plasmodium parasitemia, none were co-infected with Plasmodium parasites and arboviruses. This study highlights the presence and relative importance of zoonotic VBPs in both study areas.
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Rock, Kat. "How much do we care about biting insects? : modelling the dynamics of vector-borne diseases." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/63017/.
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Mathematical models of disease can aid understanding of, and provide a framework for, the study of disease spread and control. Vector-borne diseases are not only amongst the most significant diseases but also require tailored mathematics to model the specific biological interactions important in their spread. A key model in vector-borne epidemiology is the Ross-Macdonald ODE model. Simplification of this model using the quasi-equilibrium assumption (QEA) allowed stability and bifurcation analysis to be performed. The QEA was then used to examine the effect of avian malaria upon the Hawaiian honeycreeper, including ecological factors such as predation and climate change. In contrast, amendments to the Ross-Macdonald model can incorporate higher levels of biological detail, specifically age and bite structure in the vector population. This was facilitated via a PDE model which led to the better understanding of biological mechanisms upon disease transmission and control. Disease-free analytic solutions of the PDE were derived, however the complexity introduced by disease necessitated the use of numerical analysis in order to solve the system. This novel PDE model enabled the study of human African trypanosomiasis. Effects of starvation and teneral susceptibility of tsetse were introduced in a way which is not possible using ODE models. This provides a new framework capable of investigating the impact of these on the control of disease.
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Veronesi, Eva. "Temperature and strain-related variation in the infection and dissemination of bluetongue virus in Culicoides." Thesis, Royal Veterinary College (University of London), 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618282.
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Merchant, Farid. "Simulating the Spread of Malaria: A Cellular Automaton Based Mathematical Model & A Prototype Software Implementation." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/31313.
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Every year three million deaths are attributed to malaria, of which one-third are of children. Malaria is a vector-borne disease, where a mosquito acts as the vector that transmits the disease. In the last few years, computer simulation based models have been used effectively to study the vector population dynamics and control strategies of vector-borne diseases. Typically, these models use ordinary differential equations to simulate the spread of malaria. Although these models provide a powerful mechanism to study the spread of malaria, they have several shortcomings. The research in this thesis focuses on creating a simulation model based on the framework of cellular automata, which addresses many shortcomings of previous models. Cellular automata are dynamical systems, which are discrete in time and space. The implementation of the model proposed can easily be integrated with EpiSims/TRANSIMS. EpiSims is an epidemiological modeling tool for studying the spread of infectious diseases; it uses social contact network from TRANSIMS (A Transport Analysis and Simulation System). Simulation results from the prototype implementation showed qualitatively correct results for vector densities, diffusion and epidemiological curves.Master of Science
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Rückert, Claudia. "Alphavirus and flavivirus infection of Ixodes tick cell lines : an insight into tick antiviral immunity." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/10063.
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Arthropod-borne viruses, arboviruses, have the ability to replicate in both vertebrates and invertebrates and are transmitted to susceptible vertebrate hosts by vectors such as mosquitoes and ticks. Ticks are important vectors of many highly pathogenic arboviruses, including the flavivirus tick-borne encephalitis virus (TBEV) and the nairovirus Crimean-Congo haemorrhagic fever virus. In contrast, alphaviruses are principally mosquito-borne and have been isolated only rarely from ticks; ticks have not been implicated as their vectors. Nevertheless, the alphavirus Semliki Forest virus (SFV) replicates in cell lines derived from many different tick species, including those of the genus Ixodes, which includes vectors of TBEV and its lesspathogenic relative Langat virus (LGTV). In vertebrate cells, arboviruses generally cause cytopathic effects; however, arbovirus infection of arthropod cells usually results in a persistent low-level infection without cell death. While little is known about antiviral immunity in tick cells, the immune system of other arbovirus vectors such as mosquitoes has been studied extensively over the last decade. In insects, pathways such as RNA interference (RNAi), JAK/STAT, Toll, Imd and melanisation have been implicated in controlling arbovirus infection, with RNAi being considered the most important antiviral mechanism. In tick cells, RNAi has been shown to have an antiviral effect, but current knowledge of other immunity pathways is limited and none have been implicated in the antiviral response. In the present study, SFV and LGTV replication in selected Ixodes spp. tick cell lines was characterised and the Ixodes scapularis-derived cell line IDE8 was identified as a suitable cell line for this project. Potential antiviral innate immunity pathways were investigated; putative components of the tick JAK/STAT, Toll and Imd pathways were identified by BLAST search using available sequences from well-studied arthropods including the fruit fly Drosophila melanogaster. Using gene silencing, an attempt was made to determine whether these pathways play a role in controlling SFV and LGTV infection in tick cell lines. Selected genes were silenced in IDE8 cells using long target-specific dsRNA and cells were subsequently infected with either SFV or LGTV. Effects of gene silencing on virus replication were assessed by quantitative real time PCR (qPCR) or luciferase reporter assay. Effects on infectious virus production were measured by plaque assay. Replication of the orbivirus St Croix River virus (SCRV), which chronically infects IDE8 cells, was also quantified by qPCR after silencing of selected genes. Interestingly, SFV or LGTV infection of IDE8 cells resulted in a significant increase in SCRV replication, possibly as a result of interference with antiviral pathways by SFV and LGTV or possibly due to diversion of cellular responses from sole control of SCRV. No evidence for an antiviral role for the JAK/STAT or Toll pathways was found in IDE8 cells. However, an antiviral effect was observed for protein orthologues putatively involved in the RNAi response. Argonaute proteins play an important role in translation inhibition and target degradation mediated by RNAi, and silencing of selected Argonaute proteins resulted in a significant increase in SFV and SCRV replication. The carboxypeptidase CG4572 is essential for an efficient antiviral response in D. melanogaster, and supposedly involved in the systemic RNAi response. A putative tick orthologue of CG4572 was identified and this appeared to be involved in the antiviral response in IDE8 tick cells. When expression of CG4572 was silenced and cells subsequently infected with SFV or LGTV, replication of both viruses was significantly increased. In addition, it was shown that three mosquito orthologues of CG4572 also had an antiviral role against SFV in Aedes mosquito cells. In conclusion, of the tick cell lines investigated, IDE8 provided a suitable model system for investigating tick cell responses against arboviruses and new insight into the nature of the tick cell antiviral response was gained.
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Shukullari, Enstela [Verfasser], and Kurt [Akademischer Betreuer] Pfister. "Parasites and vector-borne diseases in client-owned dogs in Albania / Enstela Shukullari. Betreuer: Kurt Pfister." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/1096162628/34.
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Bucheli, Tamara Mancero. "Information-use for decision-making in the vector-borne disease control programmes of Ecuador and Colombia." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250346.
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Boreham, Peter F. L. "Pathophysiological, chemotherapeutic and epidemiological studies of some parasitic infections, with special reference to vector-borne diseases." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/46968.
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Knutsson, Sofie. "Towards Mosquitocides for Prevention of Vector-Borne Infectious Diseases : discovery and Development of Acetylcholinesterase 1 Inhibitors." Doctoral thesis, Umeå universitet, Kemiska institutionen, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-119924.
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Diseases such as malaria and dengue impose great economic burdens and are a serious threat to public health, with young children being among the worst affected. These diseases are transmitted by mosquitoes, also called disease vectors, which are able to transmit both parasitic and viral infections. One of the most important strategies in the battle against mosquito-borne diseases is vector control by insecticides and the goal is to prevent people from being bitten by mosquitoes. Today’s vector control methods are seriously threatened by the development and spread of insecticide-resistant mosquitos warranting the search for new insecticides. This thesis has investigated the possibilities of vector control using non-covalent inhibitors targeting acetylcholinesterase (AChE); an essential enzyme present in mosquitoes as well as in humans and other mammals. A key requirement for such compounds to be considered safe and suitable for development into new public health insecticides is selectivity towards the mosquito enzyme AChE1. The work presented here is focused on AChE1 from the disease transmitting mosquitoes Anopheles gambiae (AgAChE1) and Aedes aegypti (AaAChE1), and their human (hAChE) and mouse (mAChE) counterparts. By taking a medicinal chemistry approach and utilizing high throughput screening (HTS), new chemical starting points have been identified. Analysis of the combined results of three different HTS campaigns targeting AgAChE1, AaAChE1, and hAChE allowed the identification of several mosquito-selective inhibitors and a number of compound classes were selected for further development. These compounds are non-covalent inhibitors of AChE1 and thereby work via a different mechanism compared to current anti-cholinergic insecticides, whose activity is the result of a covalent modification of the enzyme. The potency and selectivity of two compound classes have been explored in depth using a combination of different tools including design, organic synthesis, biochemical assays, protein X-ray crystallography and homology modeling. Several potent inhibitors with promising selectivity for the mosquito enzymes have been identified and the insecticidal activity of one new compound has been confirmed by in vivo experiments on mosquitoes. The results presented here contribute to the field of public health insecticide discovery by demonstrating the potential of selectively targeting mosquito AChE1 using non-covalent inhibitors. Further, the presented compounds can be used as tools to study mechanisms important in insecticide development, such as exoskeleton penetration and other ADME processes in mosquitoes.
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Gitonga, Robert Muraguri. "Epidemiological and financial impact of vector-borne diseases on productivity of smallholder cattle in the coastal lowlands of Kenya." Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339971.
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Harrison, Thomas A. "The impact of deer on invertebrate communities and the role of deer in vector-borne pathogen cycles." Thesis, Queen's University Belfast, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534729.
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Hahn, Nina. "Investigations into the vector competency of arthropods for two Ehrlichias: Ehrlichia risticii and Cowdria rumantium." Diss., Virginia Tech, 1990. http://hdl.handle.net/10919/39407.
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Three studies relating to the vector competency of several species of ticks and Simulium spp. (blackflies) for Ehrlichia risticii, causative agent of Potomac horse fever (PHF) and Amblyomma variegatum for Cowdria ruminantium, causative agent of heartwater, are described.
Dermacentor variabilis, Rhipicephalus sanguineus, Amblyomma americanum and Ixodes scapularis ticks were investigated for their ability to acquire and transmit PHF. Larval and nymphal ticks were exposed to E. risticii by feeding on mice inoculated with the organism. Molted exposed ticks were then allowed to feed on susceptible ponies or mice and were examined by light and electron microscopy. No evidence of transmission, either clinically or by seroconversion in mice or ponies was observed.
Blackflies (Simulium spp.) were trapped in an area endemic for PHF and inoculated into mice in an attempt to demonstrate I. risticii. No evidence of seroconversion by mice to E. risticii was observed.
Two laboratory colonies of Amblyomma variegatum ticks were investigated for their ability to acquire and transmit C. ruminantium and was febrile. Nymphs from both laboratory groups were simultaneously fed on a goat that had been infected with C. ruminantium and was febrile. Engorged nymphs from both groups were replete from feeding on three consecutive days. Nymphs from both groups were then incubated under identical conditions until molting.Ph. D.
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Nordwall, Malin. "New Zealand as a model for vector borne disease emergence : Effects of social and environmental factors on dengue." Thesis, Stockholm University, Stockholm Resilience Centre, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-41256.
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The geographic distribution of dengue fever has increased worldwide in recent years and is at present the most widespread vector borne viral disease in the world (Halstead 2002). Because of its rapid spread and increasing seriousness of its complications it is considered to be the most troubling vector borne disease (Wilcox and Colwell 2005, Phillips 2008). Dengue fever is the one vector borne disease that poses the greatest threat to New Zealand. Imported cases are being reported in ever increasing numbers and all the components for a mosquito borne disease cycle is already present (Ministry of Health 1997). Furthermore, New Zealand’s geographic isolation makes it a unique location for studying the emergence of vector borne diseases, such as dengue. The objective of this thesis was - by using case studies on dengue fever on a global scale and the potential emergence of the disease in isolated New Zealand as examples – to explore the interlinkages between global changes (climate change and rapid urbanisation), globalisation (rapid travel and trade), and their local impacts on vulnerability and health (i.e. changes in local climate, travel and trade patterns and demographic changes that affect emergence and transmission of disease). This was done by 1) reviewing the ecological and environmental conditions necessary for dengue transmission; 2) examining key social and environmental factors contributing to the recent global increase in dengue fever and dengue hemorrhagic fever (DHF) and 3) drawing projections to 2070 in order to build future scenarios for epidemic dengue risks in New Zealand. Regression analysis were used to analyse 16 years of area specific dengue rates from 232 geographical areas in relation to key social and environmental factors proposed to contribute to dengue emergence. The results were tested on the mainland of New Zealand in order to build future scenarios for epidemic dengue risks in New Zealand for 2070. The outcome from the regression analysis proved to have a good ability to predict dengue rates based on national characteristics and it predicted a nearly fourfold increase in risk of epidemic for New Zealand’s North Island based on climate projections for 2070. The projected increase in population density however, had much less of an effect on the perceived risk than the projected climate change despite an estimated increase of 33% in population density. This is the first study that makes an attempt to measure the relative importance of different social and environmental variables proposed to contribute in the recent global increase in dengue.
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Ehlers, Julian [Verfasser], and Jörg [Akademischer Betreuer] Ganzhorn. "Investigations on the abundance of ectoparasites and vector-borne pathogens in southwest Madagascar / Julian Ehlers ; Betreuer: Jörg Ganzhorn." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2020. http://d-nb.info/1214370411/34.
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Liebig, Katrin [Verfasser], Stefanie [Akademischer Betreuer] Becker, Klaus [Akademischer Betreuer] Jung, and Gerhard [Akademischer Betreuer] Dobler. "Competence of the vector restricting tick-borne encephalitis virus spread / Katrin Liebig ; Stefanie Becker, Klaus Jung, Gerhard Dobler." Hannover : Stiftung Tierärztliche Hochschule Hannover, 2020. http://d-nb.info/1224232917/34.
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Faverjon, Céline. "Risk based surveillance for vector-borne diseases in horses : combining multiple sources of evidence to improve decision making." Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22604/document.
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Les maladies émergentes à transmission vectorielle sont une préoccupation croissante et particulièrement lorsqu’elles affectent les chevaux, une population spécifiquement à risque vis-à-vis de la propagation de maladies. En effet, les chevaux voyagent fréquemment et, malgré l’impact sanitaire et économique des maladies équines, les règlementations sanitaires et les principes de biosécurité et de traçabilité censés assurer la sécurité des mouvements d'équidés ne sont pas toujours en place. Notre travail propose d'améliorer la surveillance des maladies à transmission vectorielle chez les chevaux en utilisant différentes méthodes pour estimer la probabilité d'émergence d'une maladie. Tout d'abord, nous avons développé un modèle quantitatif et spatio-temporel combinant différentes probabilités pour estimer les risques d'introduction de la peste équine et de l’encéphalose équine. Ces combinaisons permettent d’obtenir une image plus détaillée du risque posé par ces agents pathogènes. Nous avons ensuite évalué des systèmes de surveillance syndromique par deux approches méthodologiques: l'approche classique avec un seuil d'alarme basé sur un multiple de l'erreur standard de prédiction, et l'approche bayésienne basée sur le rapport de vraisemblance. Nous avons travaillé ici principalement sur la détection précoce du virus West Nile en utilisant les symptômes nerveux des chevaux. Les deux approches ont fourni des résultats prometteurs, mais l’approche bayésienne était particulièrement intéressante pour obtenir un résultat quantitatif et pour combiner différentes informations épidémiologiques. Pour finir, l'approche bayésienne a été utilisée pour combiner quantitativement différentes sources d'estimation du risque : surveillance syndromique multivariée, et combinaison de la surveillance syndromique avec les résultats d’analyses de risques. Ces combinaisons ont données des résultats prometteurs. Ce travail, basé sur des estimations de risque, contribue à améliorer la surveillance des maladies à transmission vectorielle chez les chevaux et facilite la prise de décision. Les principales perspectives de ce travail sont d'améliorer la collecte et le partage de données, de mettre en oeuvre une évaluation complète des performances des systèmes de surveillance multivariés, et de favoriser l'adoption de ce genre d’approche par les décideurs en utilisant une interface conviviale et en mettant en place un transfert de connaissanceEmerging vector-borne diseases are a growing concern, especially for horse populations, which are at particular risk for disease spread. In general, horses travel widely and frequently and, despite the health and economic impacts of equine diseases, effective health regulations and biosecurity systems to ensure safe equine movements are not always in place. The present work proposes to improve the surveillance of vector-borne diseases in horses through the use of different approaches that assess the probability of occurrence of a newly introduced epidemic. First, we developed a spatiotemporal quantitative model which combined various probabilities in order to estimate the risk of introduction of African horse sickness and equine encephalosis. Such combinations of risk provided more a detailed picture of the true risk posed by these pathogens. Second, we assessed syndromic surveillance systems using two approaches: a classical approach with the alarm threshold based on the standard error of prediction, and a Bayesian approach based on a likelihood ratio. We focused particularly on the early detection of West Nile virus using reports of nervous symptoms in horses. Both approaches provided interesting results but Bayes’ rule was especially useful as it provided a quantitative output and was able to combine different epidemiological information. Finally, a Bayesian approach was also used to quantitatively combine various sources of risk estimation in a multivariate syndromic surveillance system, as well as a combination of quantitative risk assessment with syndromic surveillance (applied to West Nile virus and equine encephalosis, respectively). Combining evidence provided promising results. This work, based on risk estimations, strengthens the surveillance of VBDs in horses and can support public health decision making. It also, however, highlights the need to improve data collection and data sharing, to implement full performance assessments of complex surveillance systems, and to use effective communication and training to promote the adoption of these approaches
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Ehlers, Julian Verfasser], and Jörg U. [Akademischer Betreuer] [Ganzhorn. "Investigations on the abundance of ectoparasites and vector-borne pathogens in southwest Madagascar / Julian Ehlers ; Betreuer: Jörg Ganzhorn." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2020. http://nbn-resolving.de/urn:nbn:de:gbv:18-105085.
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Fischer, Dominik Verfasser], and Carl [Akademischer Betreuer] [Beierkuhnlein. "Applying regional climate change projections for spatio-temporal risk analyses of vector-borne diseases / Dominik Fischer. Betreuer: Carl Beierkuhnlein." Bayreuth : Universitätsbibliothek Bayreuth, 2012. http://d-nb.info/1020016558/34.
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Al-Mrabeh, Ahmad. "Aphid-borne viruses of potato : investigations into virus/host/vector interactions, serological detection using recombinant antibodies and control strategies." Thesis, University of Newcastle Upon Tyne, 2011. http://hdl.handle.net/10443/1181.
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Potato is one of the most important food crops in the world, and viruses are largely responsible for the degeneration of this vegetatively propagated crop. At least 35 viruses have been reported to infect potato naturally. The majority and the most economically important ones are vectored by aphids. The objective of this study was to conduct molecular and biological investigations into virus transmission mechanisms, including developing diagnostic methods to help to control the spread of aphid-borne potato viruses, and disrupting the vectoring ability of their aphid vectors by insecticide spray. One way to control the spread of aphid-borne viruses is to control their aphid vector, but this is not always feasible as the majority of aphid-borne potato viruses, including the most important ones, are transmitted non-persistently, being acquired within a very short time before agrochemicals can act. Thus an alternative approach to controlling this class of viruses is through a full understanding of the interaction between the virus, the host plant and the aphid vector, which was the first objective of this project. In this respect, some aphid cuticle proteins were identified to interact with potato virus Y helper component (HC-Pro) through screening of an aphid cDNA expression library, and their potential role in virus transmission was discussed. Moreover, the concept of short retention of non-persistent viruses inside their aphid vectors was challenged; the results show that PVY can be retained inside its aphid vector for a long time but it is not transmissible. This novel finding together with binding to aphid cuticle proteins, generated some new ideas about transmission mechanisms that were proposed and discussed. In addition, the effect on aphid vectoring ability of the plants used to rear aphid colonies, as a virus source, and as a virus recipient was investigated. From laboratory studies of aphid transmission, it was concluded that the transmission efficiency of PVY was significantly affected by the host plant species used to rear M. persicae, or that used as a virus recipient plant. The availability of sensitive and cheap virus detection methods is critical for early detection and control of potato viruses. In this project a sensitive fully recombinant ELISA was developed and validated for routine testing of potato leafroll virus. This technology can be applied to detect other potato viruses and has the potential to replace the commonly used immune reagent antisera.
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Belhouchet, Mourad. "Analysis of an anti-silencing mechanism involved in immune evasion by vector-borne dsRNA animal viruses of family Reoviridae." Thesis, University of Oxford, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.711672.
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Bates, Tyler Alexander. "Usutu Virus: An Emerging Arbovirus Threat." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/102268.
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Mosquito-borne viruses, such as dengue virus (DENV), Zika virus (ZIKV), chikungunya virus (CHIKV), yellow fever virus (YFV), Japanese encephalitis virus (JEV), and West Nile virus (WNV) are major threats to global public health resulting in millions of infections and hundreds of thousands of deaths annually. The presence of these viruses and their increasing emergence/spread continues to escalate. Notably, Usutu virus (USUV; Genus: Flavivirus; Family: Flaviviridae) is one such pathogen currently causing mass die-offs of avian hosts throughout Europe.
USUV is categorized in the Japanese Encephalitis virus (JEV) antigenic complex and thus shares many antigenic and pathologic characteristics with fellow members, such as JEV and WNV. Respective to human infections, USUV cases are generally asymptomatic; nonetheless, acute cases have been reported. These acute cases typically cause mild symptoms, such as fevers and rashes; however, more severe cases can result in neurologic diseases, such as encephalitis and/or meningoencephalitis.
In addition to these pathologic similarities, USUV shares several ecological and geographical traits with WNV, a pathogen responsible for several outbreaks during its spread from Africa, to Europe, and eventually the United States. Currently, WNV is considered endemic in areas across the United States due to its transmission via Culex spp.; mosquitoes that are ubiquitous in the United States. These parallels suggest the possible emergence of USUV into the United States and therefore, it is imperative to broaden our knowledge of USUV and assess its potential to become a major global health concern.
The overall goal of this thesis was to characterize USUV and evaluate its emergence potential in the United States by: (1) developing infectious clones of recent European and African USUV isolates as tools for characterization and analysis of USUV and (2) assessing the transmission potential of several species of North American mosquitoes. In Aim 1, we show that the aforementioned infectious clones infect and replicate similarly to their parental strains in vitro in both vertebrate and invertebrate models, as well as in transiently immunocompromised CD-1 and IFNAR-/- murine models, and thus serve as useful tools for future molecular studies focusing on USUV. Furthermore, in Aim 2, we describe the ability of field-caught (Southwest Virginia, USA) Culex spp. and Aedes spp. mosquitoes to become infected with a recent European isolate of USUV; although, we report an overall limited potential for these species to transmit this virus.
Altogether, these studies form a foundation for understanding the potential emergence of USUV in the United States as well as provide necessary tools needed to aid future research on USUV emergence, transmission, and pathogenesis.Master of Science
Usutu virus (USUV) is an emerging mosquito-borne virus that was first isolated from a mosquito in 1959 in South Africa, and since then, has become a major problem throughout Africa and Europe causing acute to severe infection in dozens of patients. Additionally, this virus is causing massive die-offs in Eurasian blackbird populations. This is particularly problematic because birds play a critical role in ecosystems as they act as forms of pest control, pollinators, and seed dispersers. Depletion of these species could lead to an imbalance and, eventually, collapse of our natural ecosystem. Additionally, there is a growing concern of USUV making its way into the United States, following a similar track of emergence to WNV's introduction in New York in 1999 and its subsequent spread throughout the states. WNV's introduction to the United States was detrimental to native bird populations and humans, and has caused tens of thousands of infections and thousands of deaths since this introduction. Research has shown USUV causes similar disease symptoms to WNV. The self-limiting illness from these viruses typically includes fever and rashes but some infections can result in more severe cases causing inflammation of the brain and surrounding areas. Like many other prominent mosquito-borne viruses, there is no specific treatment or vaccine for WNV or USUV. Because USUV is so closely related to WNV, and their similar characteristics may point towards similar emergence in the United States, it is essential to garner more information on USUV. The overall goal of this thesis was to establish a reliable tool(s) for further characterization of USUV and demonstrate the potential for USUV emergence in the United States. We first developed molecular tools, known as viral clones, that are valuable to the scientific community which allows the manipulation of USUV genetic material to perform further downstream studies. Our objective for this initial study was to create a molecular tool that would behave similarly to their natural, or "parental", virus. The results from this study suggest we have successfully produced these tools. Furthermore, we sought to determine the potential for field-caught mosquitoes from Southwest Virginia, USA to transmit a recently isolated strain of USUV. These data suggest that while these mosquitoes do have the ability to become infected with USUV, they have a limited potential to transmit this virus to animal hosts. Altogether, these studies have allowed us to expand our knowledge on USUV's potential emergence in the United States and develop powerful tools to continue this essential research.
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Lambert, Rebecca Click. "Chagas Disease in the United States: the Emerging Threat and the Role Climate and Awareness Play in Its Spread." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/42377.
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This study evaluates the roles of temperature variability and disease awareness in the emergence of Chagas disease (American trypanosomiasis). Chagas disease is endemic in Latin America and primarily spreads to humans directly via the triatomine vector. Hosts for most triatomine species are mainly rodents and occasionally dogs. The disease itself is caused by a parasitic protozoan, Trypanosoma cruzi (T. cruzi) which is found in the triatomineâ s feces and is often spread while the triatomine is consuming a blood meal. T. cruzi from feces enters the body via an abrasion on the skin, the mucous membranes, conjunctivae, or through consumption.
To determine the risk of Chagas disease transmission one must define qualities that make the triatomine an effective disease vector as well as investigate the level of disease awareness among physicians and the population within the vectorâ s range. This thesis maps triatomine species within the U.S. that harbor T. cruzi naturally and that exhibit qualities of domesticity. These qualities are defined by whether the species bites humans and dogs as well as reports that the species has been found in the domestic setting. Ranges illustrating temperature thresholds for increased triatomine activity for 2000 and 2030 are also depicted. Additionally, outcomes of a physician survey are presented to gauge the status of Chagas disease awareness in areas at higher risk for disease transmission. Results reveal limited consideration of Chagas disease in physician diagnosis despite the higher risk range which extends through the southern U.S. and is predicted to expand significantly by 2030.Master of Science
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Cheng, Yanchao [Verfasser], and Carl [Akademischer Betreuer] Beierkuhnlein. "Assessing spatio-temporal risks of vector-borne diseases : an interdisciplinary view integrating ecological and epidemiological models / Yanchao Cheng ; Betreuer: Carl Beierkuhnlein." Bayreuth : Universität Bayreuth, 2021. http://d-nb.info/1233353381/34.
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