Dissertations / Theses: 'Vector Borne'

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Maître, Apolline. "Modulating the vector microbiota for the control of vector-borne pathogens." Electronic Thesis or Diss., Maisons-Alfort, École nationale vétérinaire d'Alfort, 2024. http://www.theses.fr/2024ENVA0005.

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Le cheptel corse, composé d'ovins, de caprins, de porcins et de bovins, est principalement élevé dans des systèmes d'élevage extensifs. Les interactions fréquentes entre le bétail, la faune sauvage et les populations humaines favorisent donc la circulation des tiques et des micro-organismes transmis par les tiques. Une forte prévalence de bactéries transmises par les tiques des familles Rickettsiaceae et Anaplasmataceae a été signalée chez les chèvres (Anaplasma ovis), les moutons (A. ovis), les bovins (Anaplasma marginale, Anaplasma phagocytophilum et Ehrlichia minasensis) et les tiques (Rickettsia spp.) en Corse. Certaines de ces bactéries (par exemple, A. phagocytophilum et Rickettsia sp.) sont zoonotiques et pathogènes pour l'homme. Actuellement, il n'existe pas de mesures préventives pour le contrôle des tiques et des maladies transmises par les tiques. Le microbiome des tiques est un ensemble très complexe de micro-organismes en interaction qui ont un impact sur la physiologie des tiques et leur compétence vectorielle. Récemment, nous avons montré que les vaccins anti-microbiote des tiques peuvent produire une mortalité élevée chez celles-ci pendant leur alimentation. Les vaccins anti-microbiotiques peuvent également moduler le microbiome des tiques et peuvent donc être utilisés comme outil de contrôle de la transmission des pathogènes transmis par les tiques. Dans ce projet, nous utiliserons le séquençage de nouvelle génération des amplicons 16S pour étudier la diversité taxonomique et fonctionnelle du microbiome de Rhipicephalus bursa et Hyalomma marginatum, les principales tiques vectrices de pathogènes chez le bétail en Corse. En utilisant les réseaux de co-occurrence et la détection à haut débit des pathogènes, nous identifierons ensuite les bactéries clés interagissant avec les pathogènes détectés transmis par les tiques. Les bactéries clés de voûte seront utilisées pour formuler des vaccins anti-microbiotiques afin de bloquer l'acquisition et/ou la transmission des pathogènes The Corsican livestock population, composed of sheep, goats, pigs and cattle, is mainly raised in extensive farming systems. Frequent interactions between livestock, wildlife and human populations can favor the circulation of ticks and tick-borne microorganisms. A high prevalence of tick-borne bacteria of the families Rickettsiaceae and Anaplasmataceae has been reported in goats (Anaplasma ovis), sheep (A. ovis), cattle (Anaplasma marginale, Anaplasma phagocytophilum, and Ehrlichia minasensis) and ticks (Rickettsia spp.) in Corsica. Some of these bacteria (e.g., A. phagocytophilum and Rickettsia sp.) are zoonotic and pathogenic to humans. Currently, there are no preventive measures for the control of ticks and tick-borne diseases. The tick microbiome is a very complex set of interacting microorganisms that impact tick physiology and vector competence. Recently, we have shown that tick microbiota vaccines can produce high mortality in ticks during feeding. Anti-microbiota vaccines can also modulate the tick microbiome and thus can be used as a tool to control the transmission of tick-borne pathogens. In this project, we will use next-generation sequencing of 16S amplicons to study the taxonomic and functional diversity of the microbiome of Rhipicephalus bursa and Hyalomma marginatum, the main pathogen-vector ticks in cattle in Corsica. Using co-occurrence networks and high-throughput pathogen detection, we will then identify keystone bacteria interacting with the detected tick-borne pathogens. The keystone bacteria will be used to formulate antimicrobial vaccines to block pathogen acquisition and/or transmission

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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 Veterinária This 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. N/A

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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 Philosophy Department 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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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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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 potentiels Our 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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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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PEPA, A. DELLA. "VECTOR-BORNE DISEASES IN COLONY STRAY CATS OF MILAN CITY." Doctoral thesis, Università degli Studi di Milano, 2013. http://hdl.handle.net/2434/219128.

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LEISHMANIA INFANTUM INFECTION IN STRAY CATS IN A NON-ENDEMIC AREA IN NORTHERN ITALY E. Spada, DVM, PhD, Researcher 1, A. Della Pepa, DVM 1, A. Migliazzo, DVM, PhD 2, G. Bagnagatti De Giorgi, DVM 1, R. Perego, DVM, PhD 1, D. Proverbio, DVM, PhD, Professor 1 1Dipartimento di Scienze Veterinarie per la Salute, la Produzione Animale e la Sicurezza Alimentare, Universita degli Studi di Milano, Milan, Italy 2Centro di Referenza Nazionale per le Leishmaniosi,Istituto Zooprofilattico Sperimentale della Sicilia, Palermo, Italy Tipologia: Ricerca Originale Area di interesse: Medicina interna Purpose of the work. To assess the prevalence of leishmaniosis in a large representative sample of stray cats from this non-endemic area, and to analyze the results according to clinical, laboratory and infectious data 2. MOLECULAR STUDY ON VECTOR-BORNE INFECTIONS IN URBAN STRAY COLONY CAT IN NORTHENRN ITALY Eva Spada§, DVM, PhD, Researcher Daniela Proverbio§, DVM, PhD, Professor Alessandra Della Pepa§, DVM Paola Galluzzo*, Biologist Roberta Perego§, DVM, PhD Giada Bagnagatti De Giorgi§, DVM Abstract Feline vector-borne diseases are caused by a wide range of pathogens, which are transmitted by arthropods. Many of these infections have zoonotic implications and feral cats may potentially act as sentinels of human and pet health. The present study investigated the prevalence of vector-borne infections in feral colony cats in the city of Milan in northern Italy. Blood samples from 260 feral cats were evaluated, with conventional PCR, for the presence of DNA associated with hemoplasmas (Mycoplasma haemofelis and Mycoplasma haemominutum), Rickettsia spp., Anaplasma phagocytophilum, Ehrlichia spp. and Babesia microti. Odd ratios (OR) were calculated to identify risk factors for infection with vector-borne pathogens. Positive PCR was found in 156 out of 260 subjects (60%), with a prevalence of 33.1% for hemoplasmas, 31.9% for Rickettsia spp., 17.7% for A. phagocytophilum , 6.7% for Ehrlichia spp. (out of 30 samples), and 1.2% for B. microti spp (out of 168 samples). Statistical analysis revealed a correlation between infections with Rickettsia spp. and hemoplasmas (OR=1.95, P=0.02). Additionally, Rickettsia spp. infection was associated with ocular infection (OR=2.21, P=0.02). We conclude that vector-borne infections, including zoonotic diseases, are present in feral cats of Milan. Thus, domestic cats exposed to the outdoors should be routinely monitored and treated for ectoparasites to minimize disease onset and potential transmission of zoonotic agents to humans. Moreover, as these vector-borne infections are transmitted through blood, feline blood donors from this area should be screened by PCR.

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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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Moschini, Pamela M. "Mathematical models for vector-borne disease: effects of periodic environmental variations." Doctoral thesis, University of Trento, 2015. http://eprints-phd.biblio.unitn.it/1389/1/PhDThesis_Moschini.pdf.

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Firstly, I proposed a very simple SIS/SIR model for a general vector-borne disease transmission considering constant population sizes over the season, where contact between the host and the vector responsible of the transmission is assumed to occur only during the summer of each year. I discussed two different types of threshold for pathogen persistence that I explicitly computed: a "short-term threshold" and a "long-term threshold". Later, I took into account the seasonality of the populations involved in the transmission. For a single season, the model consists of system of non linear differential equations considering the various stages of the infection transmission between the vector and the host population. Assuming the overwintering in the mosquito populations, I simulated the model for several years. Finally, I studied the spatial spread of a vector-borne disease throught an impusive reaction-diffusion model and I showed some simulations.

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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 mututaliste Numerous 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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Federico, Stefano. "Towards innovative tools against vector-borne diseases: focusing on Plasmodium and Leishmania spp." Doctoral thesis, Università di Siena, 2022. http://hdl.handle.net/11365/1194525.

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Up to date, the World Health Organization (WHO) recognizes twenty conditions belonging to neglected tropical diseases (NTDs) caused by parasites, viruses, bacteria, and snake envenoming that affect some of the World’s poorest areas, predominantly in Africa, Asia, and the Americas. NTDs, that affect more than a billion people worldwide, are referred to as “neglected” as they receive inadequate attention, e.g., in terms of research funding, when compared to other diseases. Of the twenty NTDs recognized by the WHO, twelve are caused by parasites. Based on data provided by the 2019 Global Burden of Disease Study (GBD), over 20 million disability adjusted life years (DALYs) are caused by NTDs and approximately 750,000 people died because of NTDs and malaria. Taken together, these data lead malaria and NTDs to be the 15th leading cause of death worldwide. Regarding malaria, based on our previous study on bridged bicyclic 2,3-dioxabicyclo[3,3,1]dioxanes as antimalarial agents, in this work we aimed at improving the potency and the pharmacokinetic profiles of the latter by developing two new classes of bridged bicyclic endoperoxides. The introduction of protonable chains at R1 led to a marked increase in potency with respect to previous derivatives; additionally, the introduction of until-now unexplored triazine-based R1 substituents paved the way for the rational design of novel optimized antimalarial agents. Both classes of endoperoxides showed good inhibitory potency toward P. falciparum, and these results were also rationalized by in silico analysis of the interaction between the peroxide bridge and Fe(II)-heme. Furthermore, taking inspiration from the anticancer properties of ART-derived dimers, three new sets of endoperoxide-based dimers were designed and synthesized. The study design aimed at unveiling the main feature required for the explication of the antitumor activity. Preliminary biological investigation performed in human leukemia HL-60 cell line highlighted compounds 66d and 66g as the most promising derivatives of the series. In conclusion, 24 new chemical entities were synthesized and subjected to biological investigation. As per NTDs, we have identified 25 new chemical entities active against Leishmania (and possibly other trypanosomatids) trypanothione reductase, derived from the hit compound 138a. The potent and selective TR inhibitor 138a, identified by screening of GSK LeishBox, acts by selectively bind the TS2 binding pocket of TR (with respect to hGR). Further structural information were obtained by crystallography studies, which led to the resolution of the co-crystal structure of 138a in complex with TbTR, thus confirming the mechanism of inhibition. The intensive SAR analysis led to the identification of the most important features of the parent compound. The most promising derivatives, in terms of IC50 values against LiTR, were also evaluated in phenotypic assays against axenic amastigote and microphage-infecting promastigote life cycle stages of L. infantum. Moreover, the toxicity profile for some of the best compound was assessed in 3T3 and HepG2 cell lines to get preliminary information about the selectivity of the latter versus human hosts. Further biological studies are ongoing to validate the therapeutic potential of this new class of TR inhibitors in an in vivo murine model of Leishmania infection.

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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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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 species Dissertation (MSc)--University of Pretoria, 2017. Airports Company of South Africa (ACSA) National Research Foundation (NRF) Zoology and Entomology MSc Unrestricted

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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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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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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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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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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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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 - PhD Bionomics 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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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 MVs Vector-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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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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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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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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Kimaro, Esther. "Cattle vector-borne disease occurrence and management and climate change experiences in pastoral communities in Northern Tanzania." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/18812.

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The livestock sector is vital to Tanzanian economy, and pastoralists largely depend on livestock production for their livelihood. The Vector-Borne Diseases (VBDs) of cattle, East Coast fever (ECF) and African animal trypanosomosis (AAT), whose occurrence are known to be influenced by climatic conditions, cause substantial cattle production losses in pastoralist communities that may be heightened with climate change. However, little is documented on pastoralists’ experiences and observations on climate change and ECF and AAT occurrence. Further, information on management practices for ECF and AAT is outdated following privatisation of veterinary services in Tanzania. This research employed 10 randomly selected villages of Monduli District in Northern Tanzania in 2014-2015. The study explored pastoralist indigenous knowledge of the relationship between climate parameters (temperature and rainfall) and ECF and AAT using participatory epidemiology approaches. The study also quantified the seasonal prevalence of Theileria parva and trypanosome infection in 960 cattle during the wet and dry seasons. Entomological surveys for brown ear ticks (Rhipicephalus appendiculatus) and tsetse flies (Glossina spp.) were also carried out. Assessment of management practices for ECF and AAT, seasonal movements and wildlife interactions in Maasai ecosystem were investigated. This research was the first to explore pastoralists’ understanding, observation and experiences on climate parameters and ECF and AAT. The findings on seasonal prevalence of T. parva and trypanosome infection will help inform decision-making on current and future cattle VBD control strategies. In addition, the information gathered from this thesis will inform the design and implementation of active surveillance, better control and preventive strategies to manage vectors and cattle vector-borne diseases in a changing climate in pastoral communities.

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Marini, Giovanni. "The importance of climatic and ecological factors for vector-borne infections: Culex pipiens and West Nile virus." Doctoral thesis, Università degli studi di Trento, 2017. https://hdl.handle.net/11572/368006.

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About three quarters of human emerging infectious diseases are caused by zoonotic pathogens, and many of them are spread by vectors such as mosquitoes. Mathematical models nowadays represent very powerful tools to make investigations and predictions for biological dynamical systems, providing helpful insights that can be extremely valuable for several aims. In this thesis, we will focus on a particular mosquito-borne zoonosis, West Nile virus (WNV), a flavivirus of emerging public health relevance in Europe and North America, and its main European vector, Culex pipiens mosquitoes. As the transmission of mosquito-borne diseases is largely driven by the abundance of the vector, to design appropriate control strategies it is crucial to understand the population dynamics of existing vector populations and evaluate how it depends on biotic and environmental factors. This thesis presents some new mathematical models that provide insights on several aspects of mosquito population dynamics by using different statistical and computational approaches, including for instance Linear Models and Markov chain Monte Carlo technique. Specifically, they aim to study the effect of biotic and abiotic factors on Cx. pipiens dynamics by using adult mosquito trapping data, gathered over several years in Northern Italy, to feed theoretical models. Furthermore, the effects of host competition and vector feeding preferences on the dynamics of a vector-borne infection (such as WNV) are investigated through a more theoretical study.

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Marini, Giovanni. "The importance of climatic and ecological factors for vector-borne infections: Culex pipiens and West Nile virus." Doctoral thesis, Università degli studi di Trento, 2017. http://hdl.handle.net/10449/40146.

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About three quarters of human emerging infectious diseases are caused by zoonotic pathogens, and many of them are spread by vectors such as mosquitoes. Mathematical models nowadays represent very powerful tools to make investigations and predictions for biological dynamical systems, providing helpful insights that can be extremely valuable for several aims. In this thesis, we will focus on a particular mosquito-borne zoonosis, West Nile virus (WNV), a flavivirus of emerging public health relevance in Europe and North America, and its main European vector, Culex pipiens mosquitoes. As the transmission of mosquito-borne diseases is largely driven by the abundance of the vector, to design appropriate control strategies it is crucial to understand the population dynamics of existing vector populations and evaluate how it depends on biotic and environmental factors. This thesis presents some new mathematical models that provide insights on several aspects of mosquito population dynamics by using different statistical and computational approaches, including for instance Linear Models and Markov chain Monte Carlo technique. Specifically, they aim study the effect of biotic and abiotic factors on Cx. pipiens dynamics by using adult mosquito trapping data, gathered over several years in Northern Italy. Furthermore, the effects of host competition and vector feeding preferences on the dynamics of a vector-borne infection (such as WNV) are investigated through a more theoretical study.

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Marini, Giovanni. "The importance of climatic and ecological factors for vector-borne infections: Culex pipiens and West Nile virus." Doctoral thesis, University of Trento, 2017. http://eprints-phd.biblio.unitn.it/1996/1/Marini_PhD_thesis.pdf.

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Abstract:

About three quarters of human emerging infectious diseases are caused by zoonotic pathogens, and many of them are spread by vectors such as mosquitoes. Mathematical models nowadays represent very powerful tools to make investigations and predictions for biological dynamical systems, providing helpful insights that can be extremely valuable for several aims. In this thesis, we will focus on a particular mosquito-borne zoonosis, West Nile virus (WNV), a flavivirus of emerging public health relevance in Europe and North America, and its main European vector, Culex pipiens mosquitoes. As the transmission of mosquito-borne diseases is largely driven by the abundance of the vector, to design appropriate control strategies it is crucial to understand the population dynamics of existing vector populations and evaluate how it depends on biotic and environmental factors. This thesis presents some new mathematical models that provide insights on several aspects of mosquito population dynamics by using different statistical and computational approaches, including for instance Linear Models and Markov chain Monte Carlo technique. Specifically, they aim to study the effect of biotic and abiotic factors on Cx. pipiens dynamics by using adult mosquito trapping data, gathered over several years in Northern Italy, to feed theoretical models. Furthermore, the effects of host competition and vector feeding preferences on the dynamics of a vector-borne infection (such as WNV) are investigated through a more theoretical study.

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Ciocchetta, Silvia. "The vector potential of the mosquito Aedes koreicus." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/119157/1/Silvia%20Ciocchetta%20Thesis.pdf.

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Despite the recent establishment and spread of Aedes koreicus mosquitoes in Europe, its natural history and its potential public health impact remain poorly described. This thesis provides the first detailed insights into the biology of Aedes koreicus and its capacity to transmit arboviral diseases. Field work in Italy evaluated a variety of surveillance techniques for this species and its propensity to bite humans. A laboratory colony established in Australia was used to characterise its reproductive biology and its ability to transmit chikungunya virus. The findings help us understand the invasion risks and the public health threat posed by Aedes koreicus

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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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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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Dissertations / Theses on the topic 'Vector Borne'

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