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Boissier, Jérôme. "Sexe et schistosome : écologie des interactions hôte-parasite et parasite-parasite." Perpignan, 2001. http://www.theses.fr/2001PERP0478.
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Le cycle biologique du genre Schistosoma est analysé à travers les interactions hôte-parasite en fonction du sexe de l'infestation et à travers les interactions parasite-parasite sexe-dépendantes. L'analyse des interactions hôte-parasite en fonction du sexe de l'infestation révèle que les mâles schistosomes induisent une plus grande pathogénie que les femelles schistosomes aussi bien chez l'hôte mollusque que chez l'hôte vertébré. Chez l'hôte mollusque, les fonctions de nutrition, de relation et de reproduction sont plus affectées par un parasite mâle que par un parasite femelle. Chez l'hôte vertébré, la pathogénie dépend du sexe de l'hôte et du sexe du parasite. Les souris femelles sont plus affectées que les souris mâles et le parasite mâle stimule plus le système immunitaire de son hôte que le parasite femelle. Cette différence de pathogénie entre le mâle et la femelle révèle des stratégies différentes d'évolution au cours du cycle biologique des schistosomes. Les interactions parasite-parasite sont analysées aussi bien chez l'hôte mollusque que chez l'hôte vertébré. Chez l'hôte mollusque, la présence simultanée des deux sexes du parasite stimule la réussite de développement des larves infestantes émises par ce mollusque. Chez l'hôte vertébré, nous mettons en évidence des interactions intra et intersexes. Les femelles génétiquement différentes entreraient en compétition (interaction intrasexe) et feraient le choix du mâle (interaction intersexe). Ces interactions sont à rapprocher des phénomènes de sélection sexuelle qui pourraient influencer les traits de vie de ces parasitesThe life cycle of the genus Schistosoma is analysed both considering the host-parasite interactions as a function of the parasite sex and the parasite-parasite sex-dependant interactions. Studies of the host-parasite interactions according to the sex of infection revealed that male schistosomes are more pathogenic than females both in the mollusc and in the vertebrate host. Concerning the mollusc host, a male-infected mollusc was more affected in its nutrition, relation and reproductive functions than a female-infected mollusc. Concerning the vertebrate host, the pathogeny depended on the sex of the host and on the sex of the parasite. Female mice were less affected than male mice and male parasites had a higher stimulation on the immune system of the host than had female parasites. These differences between male and female pathogeny revealed different sexual strategies along the schistosome life cycle. The parasite-parasite interactions were analysed both in the mollusc and in the vertebrate hosts. Concerning the mollusc host, the simultaneous presence of both sexes, in a mollusc increases the development success of the larvae shed by this mollusc. Concerning the vertebrate host we showed intra and intersexes interactions. Genetically different females would complete each other (intrasexual interaction) and would choose there males (intersexual interaction). These interactions could be linked to sexual phenomena which could influence the life-history traits of these parasites
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Rakowitz, Michael. "ParaSITE." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/69401.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 1998.Includes bibliographical references (p. 71).
paraSITE proposes the appropriation of exterior ventilation systems on existing architecture to inflate pneumatic shelters that are designed for homeless people. This project involves the production of a series of inflatable prototypes, the distribution of these devices to a group of homeless people, and the subsequent use of these shelters in relation to a building.
by Michael Jonathan Rakowitz.
S.M.
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Schneider, Maria Victoria. "Modes de reproduction chez le parasitoi͏̈de solitaire Venturia canesces." Lyon 1, 2003. http://www.theses.fr/2003LYO10071.
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Venturia canescens, un parasitoi͏̈de ichneumonidé de chenilles de piralidés, a deux modes de reproduction : arrhénotoque, (mâles haploi͏̈des et femelles diploi͏̈des)) et thélytoque (des femelles vierges engendrent des filles diploi͏̈des). Cette thélytoquie n'est pas l'effet de bactéries symbiotiques. Dans le Sud de la France, les deux modes de reproduction coexistent en sympatrie. La thèse traite des questions soulevées par cette coexistence. Une étude de la distribution géographique et une analyse moléculaire des populations, ont montré l'existence d'un clone thélytoque très répandu. Cependant quelques individus thélytoques sont génétiquement très proches des individus arrhénotoques. Une importante partie de la variabilité chez les thélytoques est due à un flux génique à partir de mâles arrhénotoques. Pour mieux comprendre la coexistence des deux modes de reproduction, différents traits d'histoire de vie et compromis génétiques reflétants des différentes pressions de sélection ont été étudiés.
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Isomursu, M. (Marja). "Host–parasite interactions of boreal forest grouse and their intestinal helminth parasites." Doctoral thesis, Oulun yliopisto, 2014. http://urn.fi/urn:isbn:9789526203645.
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Abstract Parasites are an inseparable part of the life of wild birds. They may cause morbidity, mortality or reduction in fecundity. Parasite distribution in hosts is typically not uniform and many host factors (e.g. age) may affect the pattern of distribution. Under certain conditions, parasites even have the potential to regulate the host population. The grouse species of Finnish forests — the capercaillie Tetrao urogallus , the black grouse Lyrurus tetrix and the hazel grouse Tetrastes bonasia — harbour several species of intestinal helminth parasites. The populations have fluctuated in cyclic manner but the mechanisms behind the cycles are largely unknown. I studied the interactions of forest grouse and their intestinal helminth parasites by using intestinal samples collected by hunters in five game management districts during eight years (1995–2002). The most common parasite species in the samples was the nematode Ascaridia compar. Also, three species of cestodes (Skrjabinia cesticillus, Paroniella urogalli and Hymenolepis sp.) were found. Large size, male gender and age over 1 year were connected with an increased probability and intensity of A. compar infection. Juvenile grouse were commonly infected with cestodes while in adults infections were quite rare. The influence of inbreeding on the susceptibility to parasite infections was studied in the capercaillie by analysing microsatellite heterozygosity. The less heterozygous birds were more likely to be infected with A. compar and were more intensely infected suggesting negative influence of inbreeding on parasite resistance. An indirect negative effect of parasites was found by comparing bags hunted with a trained dog or without a dog. Grouse infected by cestodes were significantly more common in the dog-assisted bag. Thus, cestode infection seemed to make grouse more vulnerable to canine predation. The interaction between grouse population dynamics and parasites was studied by analyzing the grouse densities obtained from annual wildlife counts and parasite indices. A. compar was most common and most abundant in the years of grouse population decline. The grouse population growth rate was negatively correlated with the annual mean abundance of A. compar. Relative survival but not breeding success decreased as the abundance of A. compar increased. The findings suggest that A. compar influences the dynamics of Finnish grouse even though regular cyclic dynamics are no longer evidentTiivistelmä Loiset kuuluvat erottamattomana osana luonnonvaraisten lintujen elämään. Ne voivat aiheuttaa sairautta, kuolleisuutta tai hedelmällisyyden alentumista. Tyypillisesti loiset ovat levinneet isäntäpopulaatioon epätasaisesti ja monet isännän ominaisuudet (esim. ikä) vaikuttavat levinneisyyteen. Tietyissä oloissa loiset voivat jopa säädellä isäntäpopulaatiotaan. Suomalaiset metsäkanalinnut — metso Tetrao urogallus, teeri Lyrurus tetrix ja pyy Tetrastes bonasia — ovat useiden suolistoloismatolajien isäntiä. Metsäkanapopulaatiot ovat vaihdelleet syklisesti, mutta syklejä aiheuttavat mekanismit ovat yhä tuntemattomia. Tutkin metsäkanalintujen ja niiden suolistoloisten välisiä vuorovaikutuksia käyttäen metsästäjien vuosina 1995–2002 viidestä eri riistanhoitopiiristä keräämiä suolistonäytteitä. Yleisin loislaji näytteissä oli kanalintusuolinkainen, Ascaridia compar. Myös kolme heisimatolajia (Skrjabinia cesticillus, Paroniella urogalli ja Hymenolepis sp.) todettiin. Suuri koko, koirassukupuoli ja yli yhden vuoden ikä olivat yhteydessä suurempaan kanalintusuolinkaistartunnan todennäköisyyteen ja voimakkuuteen. Nuorilla (alle 1 v.) linnuilla heisimadot olivat yleisiä, kun taas aikuisilla tartunnat olivat varsin harvinaisia. Sisäsiittoisuuden vaikutusta loistartuntaherkkyyteen tutkittiin metsolla mikrosatelliittiheterotsygotian perusteella. Vähemmän heterotsygoottiset metsot olivat todennäköisemmin ja voimakkaammin suolinkaisten infektoimia, mikä viittaa sisäsiittoisuuden negatiiviseen vaikutukseen loisten vastustuskykyyn. Loisten epäsuora haitallinen vaikutus havaittiin, kun verrattiin koiran kanssa ja ilman koiraa metsästettyä lintusaalista. Heisimadot olivat selvästi yleisempiä linnuilla, jotka oli metsästetty koiran kanssa kuin ilman koiraa metsästetyillä. Heisimatotartunta näytti siis altistavan metsäkanoja koiraeläinten saalistukselle. Metsäkanalintu- ja loispopulaatioiden välistä vuorovaikutusta tutkittiin analysoimalla vuosittaisia metsäkanatiheyksiä ja loisten runsautta. Kanalintusuolinkainen oli yleisimmillään ja runsaimmillaan metsäkanatiheyden laskuvuosina. Metsäkanapopulaation vuosittainen kasvuvauhti korreloi negatiivisesti kanalintusuolinkaisen vuosittaisen runsauden kanssa. Suhteellinen elossasäilyvyys laski kanalintusuolinkaisen runsauden lisääntyessä, mutta lisääntymistuloksen suhteen ei ollut samaa ilmiötä. Löydökset viittaavat siihen, että kanalintusuolinkaisella on vaikutusta suomalaisten metsäkanalintukantojen vaihteluihin, vaikka syklisiä kannanvaihteluja ei enää havaitakaan
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St, Vincent Chad Michael. "'Parasite single' women of Japan : 'parasites' or search for a new identity? /." Title page, contents and introduction only, 2002. http://web4.library.adelaide.edu.au/theses/09AR/09ars7749.pdf.
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Goodhead, Ian Barry. "Genomic approaches to understanding host resistance and parasite virulence in Trypanosoma parasites." Thesis, University of Liverpool, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.570185.
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Roughly one-third of cattle in sub-Saharan Africa are at risk of contracting "Nagana" - a disease caused by Trypanosoma parasites similar to those that cause human "Sleeping Sickness". Laboratory mice can also be infected by trypanosomes, and different mouse breeds show varying levels of susceptibility to infection, similar to what is seen between breeds of cattle. We have applied next-generation technologies to identify shared polymorphisms between susceptible mice, and annotated these for potential function alongside publicly available SNP data sets. By so doing, short lists of genes at the QTL have been created to aid functional testing in cattle. This includes two promising 'candidate genes': Pram1 and Cd244, which can now be tested to confirm their effect on response to trypanosome infection. The human-infective parasite Trypanosoma brucei rhodesiense generally causes an acute form of "sleeping sickness" across Eastern Africa, compared to the more chronic T b. gambiense infections found in Western Africa. The 1988-1993 Ugandan T b. rhodesiense outbreak constituted infections by parasites with differences in their clinical manifestation. Two such sub types, termed Busoga 17 (B 17) and Zambesi 310 (Z31O), caused more acute, and more chronic infections, respectively. In order to investigate whether the major QTL that regulates survival in T congolense infections (Tir 1) does so in a similar manner in T b. rhodesiense, mice congenic for the C5 7BL/ 6 allele (Tirl CC) at Tir 1 were infected with Z310 and B 1 7 zymodeme T b. rhodesiense parasites. Whilst Tir 1 was not found to have a significant effect on survival, all mice had a significantly shorter mean survival time when infected with B 17 (~1O. 7 days) than those infected with Z31 0 (~15.6 days), in line with previous observations of human infections. In order to identify genetic loci that might underlie differences in virulence between T b. rhodesiense zymodemes, cluster analysis was performed on the microsatellite genotypes of 31 T b. rhodesiense isolates that represented nine different zymodemes. Despite STRUCTURE identifying three population clusters, the Z310 and B 17 parasite populations could not be distinguished, suggesting that either multiple genes control virulence, that there is gene flow between similar parasite populations, or that the microsatellite genotyping is insufficient to distinguish between different parasite populations. Finally, we present the first whole-genome sequences of T b. rhodesiense field isolates, one each of Z310 and B 1 7. Genomic analysis of east African T b. rhodesiense and west African T b. gambiense has suggested that recombination may be occurring between them. SNP genotyping of 32 T b. rhodesiense isolates showed that differences in clinical phenotypes were associated with differences in alleles on chromosome 8. The genome sequence suggests that chromosome 8 is heterozygous for alleles of west African origin in the more virulent strain, suggesting that recombination may be associated with parasite virulence. This suggests that the human subspecies of T brucei are not genetically distinct, which has major implications for the control of the parasite, the spread of drug resistance and understanding the variation in virulence and the emergence of human infectivity. Further genetic analysis of T b. brucei populations from Western, central and Eastern Africa may be necessary to ascertain whether recombination is occurring directly between human-infective subspecies, or in the underlying animal-infective population.
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Ferté, Hubert. "Les nématodes parasites du tube digestif du chevreuil (Capreolus capreolus L. 1758) : à propos d'une enquête réalisée dans le nord-est de la France." Tours, 1987. http://www.theses.fr/1987TOUR3805.
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Mintsa, Nguema Rodrigue. "Interactions hôte-parasite dans le modèle Biomphalaria pfeifferi-Schistosoma mansoni du Dhofar (Oman) : génétique des populations de l’hôte, traits d’histoire de vie et conséquences sur la transmission du parasite." Perpignan, 2010. http://www.theses.fr/2010PERP0995.
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Cette thèse a été réalisée dans le contexte de la réémergence de la schistosomose à Schistosoma mansoni (plathelminthe trématode) dans le Dhofar en Oman. Le travail est centré sur les interactions hôte-parasite et sur leurs conséquences sur la transmission du schistosome. Une première partie est consacrée à l’étude spatio-temporelle de la structure génétique des populations de Biomphalaria pfeifferi (mollusque gastéropode d’eau douce). Elle a été réalisée à l’aide de neuf marqueurs microsatellites sur 18 populations de mollusques. Les populations de B. Pfeifferi étudiées sont caractérisées par une très faible variabilité génétique intra populationnelle. Par contre, elles sont fortement différenciées génétiquement. Une différenciation temporelle a également été enregistrée dans certaines populations. Une seconde partie est consacrée à l’étude des traits d’histoire de vie et des relations hôte-parasite. Elle a été réalisée à l’aide de huit combinaisons hôte-parasite qui diffèrent soit par la population de parasite (origine humaine ou origine murine), soit par la catégorie du site (naturel ou aménagé), soit par le morphe du mollusque (pigmenté ou albinos). Les traits d’histoire de vie suivants ont été analysés : croissance, fécondité et survie de B. Pfeifferi et taux d’infestation, période prépatente et production cercarienne de S. Mansoni. Les résultats montrent que la population de S. Mansoni et le morphe de B. Pfeifferi jouent un rôle majeur dans la transmission de la schistosomose dans le Dhofar. Les résultats sont discutés en termes de compatibilité hôte-parasiteThis thesis has been conducted in the context of the reemergence of schistosomiasis caused by Schistosoma mansoni (flatworm trematode) in Dhofar (Oman). The work focuses on the host-parasite interactions and their implications on schistosome transmission. The first part is devoted to a spatiotemporal study of the population genetics of Biomphalaria pfeifferi (freshwater gastropod snail). Nine microsatellite markers were used for characterization of 18 populations of B. Pfeifferi. The results showed that intrapopulations genetic variability was very low. However, the populations were highly differentiated. Temporal differentiation was also recorded in some populations. A second part concerns to the study of the life-history traits and host-parasite relationships. It was conducted using eight host-parasite combinations that differ either by the parasite population (human versus murine), by the waterbody category (natural versus man-made) or by the morph of the snail (pigmented versus albino). The following life-history traits were analyzed: growth, fecundity and survival of B. Pfeifferi and rate of infection, prepatent period and cercarial production of S. Mansoni. The results show that both the origin of S. Mansoni and the pigmentation of B. Pfeifferi play a major role in transmission of schistosomiasis in Dhofar. The results are discussed in terms of host-parasite compatibility
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Houngbédji, Tossimidé. "Rhamphicarpa fistulosa : infestation dans les bas-fonds rizicoles de la Région des Savanes (Togo) et étude des interactions hôte-parasite." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS455/document.
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Une des contraintes biotiques majeures de la riziculture de bas-fond au nord du Togo est l’adventice parasite Rhamphicarpa fistulosa (Hochst.) Benth. Afin d’évaluer les options stratégiques pour contrôler efficacement R. fistulosa, notre étude a été conduite avec comme principaux objectifs : 1) l’identification de la répartition de R. fistulosa et l’étude des facteurs qui favorisent son infestation, 2) l’étude de l’impact des niveaux d’infestation sur la flore adventice du riz, et 3) la caractérisation des interactions hôte-parasite et de leurs impacts sur le développement de l’hôte et les performances reproductives du parasite. A l’issu des prospections de terrain, les plus fortes infestations ont été retrouvées sur des sols majoritairement à texture sableuse et très pauvres en matière organique. Une flore adventice très diversifiée a été retrouvée en présence de R. fistulosa, certaines adventices pouvant être parasitées et constituer éventuellement un réservoir pour accroître le stock semencier du parasite. En conditions contrôlées, R. fistulosa se développe et se reproduit aussi bien sur le riz que sur la tomate, alors que le soja retarde la reproduction du parasite. La germination des graines de R. fistulosa est maximale en présence de graines de plantes cultivées ou adventices. Les graines nouvellement récoltées ont une dormance de plus de six mois, mais leur germination a été stimulée par la présence de phytohormones. En conclusion, les meilleures stratégies de lutte doivent impliquer le contrôle par les semis tardifs, les rotations culturales avec les légumineuses comme le soja, l’arachide ou le niébé, et les cultures maraîchèresMain biotic constraints to rain-fed lowland rice cultivation in northern Togo include the parasitic weed Rhamphicarpa fistulosa (Hochst.) Benth. In order to evaluate efficient strategies to control R. fistulosa, our study was performed taking into account the following main objectives: 1) Identification of the distribution of R. fistulosa and study of the factors favouring its infestation, 2) Study of the impacts of infestation levels on rice weed communities, and 3) Characterization of the host-parasite interactions and their impacts on the host development and the parasite reproduction. Following fields investigations, highest infestations were observed on sandy soils with low levels of organic matter.In addition, weed flora found in the presence of R. fistulosa was much diversified and some weeds were found to been parasitized and could possibly constitute reservoirs to increase the seed stock of the parasite. In controlled experiments, R. fistulosa grown and reproduced better on rice and tomato crops, than on soybean which delayed the reproduction of the parasite. Germination of R. fistulosa seeds was stimulated in presence of cultivated crops or weeds. New collected seeds shown six months dormancy but their germination was stimulated in presence of phytohormones. In conclusion, the best strategies to control R. fistulosa must include delayed sowing, crop rotation with leguminous species (i.e. soybean, peanut or cowpea) and vegetable cropsKeywords: Rhamphicarpa fistulosa, rice, lowland, parasitism, host-parasite interaction, weeds
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Oliveira, Ana Carolina Santos. "Mecanismos parasitários de escape ao sistema imunológico." Master's thesis, [s.n.], 2011. http://hdl.handle.net/10284/2486.
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Trabalho apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Ciências Farmacêuticas.A evasão ao sistema imunulógico, por parte dos parasitas, está actualmente omnipresente e envolve uma série de mecanismos moleculares, que reflectem a evolução, reprodução e crescimento parasitário. Existem uma série de formas e processos de escape parasitário permitindo com que estes garantam, simultaneamente, a sua sobrevivência e a do hospedeiro. A co-evolução convergente entre hospedeiro e parasita sustêm a base destes mecanismos que se baseiam na manipulação dos processos que fazem parte e regulam a resposta imunitária e o normal funcionamento das células de defesa do hospedeiro, ficando a resposta inata e adaptativa vulnerável à acção parasitária. O fenómeno de evasão parasitária foi descoberto há cerca de 100 anos, por aquele que é considerado o pai da Imunologia, Paul Erlich; este durante alguns dos seus estudos observou “o desaparecimento dos receptores” característicos dos anticorpos do sistema imune, em Trypanossomas africanos. A partir daí as funções genéticas, alterações de variantes antigénicas, moléculas supressoras do sistema imune têm sido amplamente descobertas e estudadas. A importância do conhecimento das adaptações parasitárias é fundamental para o desenvolvimento de terapeuticas na área da medicina, imunologia, parasitologia e farmacologia visto que destas se obtêm dados fundamentais sobre a interecção entre estes microorganismos e sobre as patologias que podem causar. Desta feita este trabalho aborda, então esses mecanismos, explicando ainda de forma sintética a constituição do sistema imune de forma a direccionar facilmente e localizar o centro de ataque parasitário, demonstrando a forma ágil e habilidosa com que estes seres conseguem ludibriar um complexo sistema como é o sistema imunitário de um indivíduo imunocompetente. Evasion of immunologic system, by parasites, is now ubiquitous and involves several molecular mechanisms that reflect the evolution, parasite growth and its reproduction. There are a number of forms and escape processes which have been adopted by parasits ensuring survival of both parasite and host. The convergent co-evolution of host and parasite is the basis of these mechanisms that rely on manipulation of the processes which are part of the immune response and regulate it, as well as, the normal functioning of host defense cells, leaving the innate and adaptive response vulnerable to parasite activity. The phenomenon of parasite evasion was discovered about 100 years ago, by one considered the father of Immunology, Paul Ehrlich. This has been found during some of his studies where disappearance of the antibody receptors characteristic of the immune system of the African trypanosome, was observed. Since then, gene functions, changes in antigenic variants and suppressing molecules of immune system have been extensively discovered and studied. The importance of the knowledge of parasitic adaptations is crucial for the development of new therapeutics in medicine, immunology, parasitology and pharmacology since these data reflect the interaction between microorganisms and the immune system and also related diseases. With this dissertation we will have an overview of these mechanisms and a brief explanation of the immune system in order to easily locate the center of parasitic attack, demonstrating how agile and skilled these living beings can evade a complex system like the immune system of immunocompetent individuals.
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Prior, Kimberley Faith. "The evolutionary ecology of circadian rhythms in malaria parasites." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/29562.
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Biological rhythms are thought to have evolved to enable organisms to organise their activities according to the Earth’s predictable cycles, but quantifying the fitness advantages of rhythms is challenging and data revealing their costs and benefits are scarce. More difficult still is explaining why parasites that exclusively live within the bodies of other organisms have biological rhythms. Rhythms exist in the development and traits of parasites, in host immune responses, and in disease susceptibility. This raises the possibility that timing matters for how hosts and parasites interact and, consequently, for the severity and transmission of diseases. Despite their obvious importance in other fields, circadian rhythms are a neglected aspect of ecology and evolutionary biology. The ambitions of this thesis are to integrate chronobiology, parasitology and evolutionary theory with mathematical models to obtain a greater understanding about how and suggest why malaria parasites have rhythms as well as the effect of infection on host rhythms. First, I identify how malaria parasites lose their developmental rhythms in culture, when they lack any potential time cues from the host. Next, I characterise parasite rhythms inside the mammalian host in terms of synchrony and timing and demonstrate there is genotype by environment interactions for characteristics of parasite rhythms. Then, I investigate the effect that parasite infection has on host rhythms and show there is variation between parasite genotypes in their effect on host locomotor activity and body temperature rhythms during infections. Finally, I explore which host rhythms may be driving parasite synchrony and timing and demonstrate the importance of peripheral host rhythms for the timing of malaria parasite developmental rhythms. The data presented here provides novel and important information on the role of rhythms during disease and opens up a new arena for studying host-parasite coevolution.
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Vandame, Rémy. "Importance de l'hybridation de l'hôte dans la tolérance à un parasite : cas de l'acarien parasite Varroa jacobsoni chez les races d'abeille Apis mellifera européenne et africanisée, en climat tropical humide du Mexique." Lyon 1, 1996. http://www.theses.fr/1996LYO10306.
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Williams, Emily Rose-Margaret. "Parasites and the ecological undead: marine snails and their suite of trematodes." Thesis, The University of Sydney, 2012. https://hdl.handle.net/2123/28920.
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The invisible interactions between parasites and their hosts are important elements of the ecology and biology of host populations. Parasites can shape the morphology, distribution, physiology and behaviour of individual hosts - some commonly studied host-parasite interactions often involve gastropods and trematodes. Trematodes can have detrimental effects on their snail hosts, yet many such relationships are relatively unknown. One such relationship is that of the mud whelks, Velacumantus australis, many of which are infected by several species of parasitic trematode. Australian estuaries and lagoons are commonly populated with these snails. Little work has been done, however, on how these snails are affected by their trematodes. My overall aim was to create a more comprehensive picture of the relationship between trematodes and their snail hosts, since it is unknown what is occurring within populations of these snails in Australia. Through dissections and experiments, I described all the species infecting the snails, including those previously unknown to science; quantified infection prevalence within different populations of snails in New South Wales; compared infection with host size, both in situ and through growth of host bodies over time; assayed proteins and lipids from host tissues to quantify energy reserves; and finally, tested whether snails displayed different behaviours depending on infection status. My results show that parasitism varies temporally and on small and large spatial scales, most likely because of recruitment and presence of other hosts. The effects of parasitism on the host body include differences in growth and energy reserves, and appear to be influenced depending on the species of trematode. The activity and locomotory behaviour of snails is also affected by trematode infection, whether the snail has a neighbour, and the infection status of the neighbouring snail. These results show that the relationship between V australis and its trematodes is more complex than predicted and is influenced by dynamic interactions between spatial variability and parasitism. Future experiments with these snails and other snail-trematode relationships in similar systems should include different spatial scales as well as different species of trematodes in order to disentangle the relationships between parasitism and environmental variation.
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Campbell, Scott Edward. "Secreted proteins in Microsporidian parasites : a functional and evolutionary perspective on host-parasite interactions." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/14523.
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The Microsporidia form a phylum of obligate intracellular parasites known to cause disease in humans and a diverse range of economically important animal species. Once classified as ‘primitive’ eukaryotes, it is now recognised that the peculiarities of microsporidian genomics and cell biology are, in fact, the consequence of extreme reduction allowed by an intimate relationship with the host cell. Excluding survival as an extracellular spore, microsporidia are in direct contact with the host throughout their developmental lifecycle, from entry to egress. Host cell manipulations have been described in morphological terms, but despite this, characterisation of such processes at the molecular level remains challenging. The logistics of the microsporidian lifecycle suggest secreted proteins and membrane proteins with extracellular domains may be involved in virulence and implicated in host cell manipulation. This study employs bioinformatic tools to predict secreted proteins in diverse microsporidia and comparative genomics to identify conserved proteins which may be required for host cell manipulation, pathogenicity and lifecycle progression. The protein complement secreted into the extracellular environment during microsporidian spore germination, a lifecycle stage required for host cell invasion, is identified experimentally. This analysis suggests that novel microsporidian specific hypothetical proteins, that is, proteins with no functional annotation or domain, play a significant role during parasite invasion of the host and provides the first identification of potential microsporidian effector proteins. Aiming to address microsporidian pathogenicity during intracellular stages, candidate virulence factor proteins, namely a hemolysin and a protein tyrosine phosphatase are also characterised and localised in situ. Lastly, an animal-derived horizontal gene transfer event is used in conjunction with both the fossil record and molecular dating approaches to add timescale to the microsporidian diversification. This work suggests that microsporidia radiated recently, achieving extreme cellular diversity, acquiring a novel infection mechanism and undergoing vast speciation in a short evolutionary timescale, likely within the last 200 million years.
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O'Brien, Chris. "Appreciating the Importance of Parasites: Analyzing and Understanding the Ecology of Parasite-Host Interactions." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194212.
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There is a growing interest in the nature of parasite-host interactions, the role these relationships play in ecological communities, and how human activities alter these associations. Furthermore, because inference about these interactions is usually gained by methods of statistical hypothesis testing, additional importance should be placed on the analysis and interpretation of parasite-host interactions. In this dissertation I address these ideas in three separate but interrelated studies with the three following questions: 1) How do two parasites with complex life-cycles alter the behavior of a novel amphipod host, and how do host and non-host predators respond to infected amphipod prey? In contrast to other studies, I found that two parasites of an endemic amphipod at Montezuma Well had little affect on their amphipod host, and that these associations had little affect on predation rates by both host and non-host predators. Results from this study underscore the importance of further investigating novel parasite-host interactions and placing them in their phylogenetic and evolutionary context. 2) Does human recreation affect spatial patterns of infection in an otherwise natural ecosystem? This study demonstrates that human visitors to Montezuma Castle National Monument alter patterns of waterfowl space use that in turn affect spatial patterns of disease in invertebrate hosts. This is the first study to document such an effect, and I discuss the important implications of this finding. 3) How is hypothesis testing applied in studies of wildlife disease, what conclusions can we make about the relative usefulness of these methodologies, and how can the analysis and interpretation of wildlife disease studies be improved? In this final study I conducted a literature review, computed statistical power for methodologies used in the literature, and re-analyzed published data to provide an example of the advantages of my suggested approach. I conclude that many studies report findings using methods that could be more informative and some studies may lack statistical power, demonstrating the importance of using prospective power analysis in the design of future studies. Furthermore, using statistical techniques that estimate the observed effect size can aid in increasing information transfer in studies of wildlife disease.
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Grenier, Simon. "Biologie et physiologie des relations hôtes-parasitoïdes chez 3 tachinaires (Diptera, Tachinidae) d'intérêt agronomique : développement en milieux artificiels : lutte biologique." Lyon 1, 1986. http://www.theses.fr/1986LYO10004.
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Morgan, Andrew. "Experimental host-parasite coevolution." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424864.
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Jones, R. S. "Parasite-induced warning colouration." Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3006078/.
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Parasites are ubiquitous in nature and are capable of exerting strong selection pressures on their hosts to enhance (or potentially reduce) transmission. Parasite manipulation of hosts can therefore drive evolution of various traits and phenotypes in the host to the benefit of the parasite. These adaptations can serve a number of purposes, working to enhance survival and reproduction of the parasite within its host. This thesis aims to elucidate the roles of various defences induced by the nematode Heterorhabditis bacteriophora and its symbiotic bacterium Photorhabdus luminescens in its obligate insect host, in which predation of the host is fatal for the parasitic colony. To do this I utilised both laboratory and field experiments to test a number of the defences with a variety of predators. To begin with I extended a previous study examining predation rates on uninfected and infected individuals by examining the effect of background on predation rates in the field. I found that prey that were conspicuous against their background received fewer attacks and were consumed less than those that were cryptic with respect to their background, enhancing survival for the parasitic colony within infected hosts. Following this I was then able to test a number of the defences utilising ground beetles, birds and mice as predators. In a laboratory setting I tested whether beetles could use any of the parasite-induced cues to avoid predation of infected waxworm hosts. I found infections were vulnerable early on (day 3 post-infection) in terms of chemical defence as beetles would consume this infection stage to a greater extent than either day 5 or 7 post-infection waxworms. However, beetles utilised the olfactory cue to avoid predation of infected hosts across all infection stages, protecting the parasite colony. Having seen an effect of the visual cue, and perhaps olfactory cue in the initial field experiment, I decided to test both these components in concert and singly in a laboratory environment with wild-caught great tits in Finland. There was not a clear benefit to multimodality in terms of attacks but there was in terms of consumption of infected waxworms at various stages of infection. Additionally, there was evidence that the olfactory cue overshadowed the visual cue in terms of attack at various stages of infection. Having examined the visual, chemical and olfactory cues, I then tested the role of bioluminescence in this nematode-bacterium system. Utilising house mice as predators I tested both the olfactory cue and bioluminescence cue with the same experimental design under differing light conditions, where the bioluminescence was and was not visible. Unlike in other predators tested, the olfactory cue did not elicit a strong avoidance response, resulting in only discriminatory behaviour towards later stage infections (day 7 post-infection). However, I found that bioluminescence was an effective cue at causing deterrence in house mice as mice spent less time near glowing than non-glowing prey. Overall, this thesis provides novel insights into the role of defences induced by a nematode-bacterium complex in protecting the infected host carcass against predation, which is fatal for the parasitic colony. Furthermore, the thesis provides ideas for future research to develop these findings further.
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Syed, Abeer. "Microsystems for parasite enrichment." Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4353/.
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The aim of this project was to develop a lab-on-chip platform upon which activities in engineering and parasitology can be brought together to create new low cost diagnostic technologies for Human African Trypanosomiasis, a disease also known as sleeping sickness, for use in resource-poor environments like Sub-Saharan Africa. Filtration and separation of particles is essential for many biochemical and analytical assays. This work describes the development of novel techniques to enhance the separation/enrichment of parasites from whole blood. Techniques like chemotaxis, inertial microfluidics and density based separation were used to achieve the separation/enrichment. This thesis describes (i) development of an assay to confirm the chemotaxis of Trypanosoma brucei towards higher concentrations of glucose, (ii) designing, fabrication and use of inertial microfluidic device for continuous sorting of trypanosomes from blood cells, (iii) density based separation of trypanosomes from whole blood using a two phase Dextran-Ficoll system, and (iv) density based enrichment of trypanosomes using surface acoustic waves. This work represents an important step towards improving the detection of trypanosomes in blood for which microscopy is still considered to be the gold standard.
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Serne-Delaves, Micheline. ""Blastocystis hominis" Brumpt, 1912 et blastocystose humaine : un parasite méconnu, une parasitose discutée." Paris 5, 1993. http://www.theses.fr/1993PA05P017.
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Bell, Andrew Stuart. "Studies on the biosystematics and biology of strigeids (Digenea) parasitic in freshwater fish." Thesis, University of Stirling, 1995. http://hdl.handle.net/1893/3383.
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This study is concerned with two strigeid genera which utilise fish as their second intermediate host and piscivorous birds as a definitive host, i.e. Apatemon (Apatemon) Sudarikov, 1959 and Ichthyocotylurus Odening, 1969. Although the lifecycle has been ascertained for most Ichthyocotylurus spp., confusion and disagreement still exist as to the constituent species, while all of the life-stages have been described for only a single member of the subgenus Apatemon (Apatemon). In order to clarify species membership to these taxa and indeed the taxonomic position of the subgenus Apatemon (Apatemon) further information was required on the life-cycles and life-stages of these strigeids. Although, metacercariae from this family have been recorded from a variety of British fishes, confirmed records, i.e. those supported with life-cycle data, are limited to a single species. It was this lack of confidence in identifying metacercariae recovered from fishes and the lack of known good criteria for distinguishing the adults that prompted the present study. Collections of metacercariae from a variety of hosts and locations were made, from which all subsequent life-cycle stages were obtained. The project aims were to establish the identity of the forms occurring in British fishes, by applying discriminatory techniques to the experimentally reared life-stages. In addition to traditional methods, techniques with little previous application to these genera were used and included, scanning electron microscopy (SEM), chaetotaxy, principal components analysis (PCA), and karyology. Furthermore, behavioural aspects such as the release patterns of cercariae from their molluscan hosts were studied to investigate whether they would prove to be of diagnostic value. Metacercariae obtained from the sampling survey were tentatively identified, using all currently employed methods for their determination, i.e. morphology, nature of cyst, host and site specificities, as Ichthyocotylurus erraticus (Rudolphi, 1809), I. variegatus (Creplin, 1825), Apatemon gracilis (Rudolphi, 1819) and A. annuligerum (Nordmann, 1832). Material collected from Finland was considered to contain both Ichthyocotylurus spp. recovered in the U.K., as well as I. platycephalus (Creplin, 1825) and I. pileatus (Rudolphi, 1802). The Ichthyocotylurus spp. were found to be more host specific than A. gracilis, although A. annuligerum was considered oioxenic to perch Perea fluiatilis L. Records of I. erraticus from gwyniad Coregonus lavaretus (L.) and grayling Thymallus thymallus (L.), and A. gracilis from arctic charr Salvelinus alpinus (L.) constitute first listings from Britain. The large number of sensilla present on the body surface of these metacercariae, observed by SEM and chaetotaxy, precluded their diagnostic use. PCA was, however, found to be of value for distinguishing between species and determining morphological variation within a species. I. erraticus, I. variegatus and A. gracilis adults were successfully reared in experimental hosts using metacercariae from a variety of fish hosts, sites within a single fish host and geographical sites. The adults obtained enabled clarification of the identities assigned to the metacercariae. Those metacercariae believed to represent I. pileatus and A. annuligerum failed to establish in experimental hosts. Herring gulls and lesser black-backed gulls proved to be extremely good experimental hosts for both Ichthyocotylurus spp., with the vast majority of infections establishing and providing high yields of eggs and adults. These infections yielded information on the establishment, development, fecundity, site specificity, longevity and morphological variability of the adults. Aspects of the morphology and biology of I. variegatus adults recorded were found to support its validity as a species discrete from I. platycephalus which was in some doubt. The experimental hosts used for A. gracilis infections, domestic and mallard ducklings, were found to be less satisfactory. Challenges were performed with A. gracilis metacercariae from three sources, rainbow trout, salmon parr and stone loach. The latter source was the only one to result in egg producing adults, with specimens exhibiting normal morphology and demonstrating an increased longevity over adults raised from salmonid metacercariae. These findings suggest that the metacercarial host may affect the successful completion of the life-cycle. Eggs of known origin were collected for all three cultured strigeid species, enabling further life-cycle studies, these were incubated and miracidia successfully raised. Developmental periods were found to be temperature dependent and differed for the three species at 20°C: A. gracilis < I. erraticus < I. variegatus. Light microscopy revealed the morphology of all three species to be identical, as were the epidermal plate formulae and chaetotaxy, indicated by silver-staining. The nomenclature for the distribution of miracidial sensilla derived by Dimitrov et al. (1989) was amended to enable a full description of these species. Osmotic shock resulted in an improved deciliation of the miracidia compared to sonication and subsequent SEM observation confirmed the arrangement of body surface structures, while revealing sensilla forms. Behavioural aspects of I. variegatus miracidia were examined, with a maximum longevity (< 11 hours) recorded at the lowest temperature studied (l0 degrees C), and host finding demonstrated to occur by an increased turning response in the presence of substances emitted from the susceptible snail host, following an initial unresponsive dispersal phase. Ichthyocotylurus cercariae were found in naturally infected Valvata piscinalis which constitutes the first record in Britain of cercariae of this genus. Cercariae of I. erraticus and I. variegatus were successfully raised experimentally from miracidia of known identity and origin within naive, experimentally raised V. piscinalis hosts, while A. gracilis cercariae were obtained from laboratory reared Lymnaea peregra. Cercarial developmental periods within the molluscan host were found to be temperature dependent and markedly different for the strigeid genera investigated, as were their behaviour and morphology. The Ichthyocotylurus spp. exhibit a distinct diurnal emergence rhythm from their molluscan host, being shed during the hours of daylight, while A. gracilis cercariae demonstrate a reciprocal pattern, emerging during the hours of darkness. Behavioural contrasts were also observed in longevities, emergence strategies (route of exit) and swimming behaviour. The two Ichthyocotylurus spp. were extremely similar, the only cercarial features found to be of diagnostic use were: the presence or absence of eye-spots; their differing developmental periods from miracidium to cercaria; the number and distribution of sensilla when compared by PCA; and their differing longevities at 20 degrees C. Characters considered to be of value in differentiating between strigeid cercariae at the species level, including the armature, chaetotaxy pattern and resting posture, did not differ between these two species. SEM observations enabled descriptions of the variety and structure of sensilla present on different life-stages, while transmission electron microscopy revealed the internal structure of cercarial sensory structures. Experimentally raised cercariae were found to be infective and the life-cycle was completed for the three strigeid species. Host specificities were observed for I. erraticus and A. gracilis, being particularly stringent for the latter species, while site specificities recorded were as observed in natural infections. Metacercarial maturation periods (for encystment) were highly temperature dependent, being comparable for the two Ichthyocotylurus spp. and more rapid than for A. gracilis specimens.
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Pereira, Felipe Bisaggio. "Estrutura da comunidade de helmintos associados ao lagarto Tropidurus torquatus (Squamata: Tropiduridae) em uma área de afloramento rochoso no distrito de Toledos, Juiz de Fora, MG." Universidade Federal de Juiz de Fora (UFJF), 2010. https://repositorio.ufjf.br/jspui/handle/ufjf/3017.
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CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
A comunidade parasitária do lagarto Tropidurus torquatus em uma área de campo rupestre localizada no estado de Minas Gerais, sudeste do Brasil, foi estudada. Dos 110 hospedeiros analisados, 92 (83,6%) estavam infectados. Foram encontradas cinco espécies de helmintos, três de nematóide: Physaloptera lutzi, Parapharyngodon sp. e Oswaldofilaria sp., uma espécie de cestóide e um cistacanto não identificados. Apenas as espécies de nematóides apresentaram dados suficientes para analises ecológicas, sendo P. lutzi a espécie mais prevalente (67,3%) e com maior intensidade parasitária (4,86±4,85). Somente para Oswaldofilaria sp. foram encontradas diferenças significativas na prevalência e intensidade parasitária entre hospedeiros fêmeas e machos, esses últimos apresentando os maiores valores. A intensidade parasitária total e de P. lutzi também diferiram entre os sexos de hospedeiros com machos apresentando os maiores valores. O tamanho corporal do hospedeiro correlacionou-se de forma positiva com a intensidade de infecção de todas as espécies de nematóides. A sazonalidade local não influenciou de forma significativa a estrutura da comunidade componente de parasitos estudada. Aspectos do hospedeiro como dieta, dimorfismo sexual e comportamento (territorialiasmo e forrageamento) representaram importantes fatores na determinação da estrutura dessa comunidade de helmintos. De maneira geral, a comunidade parasitária apresentou baixa riqueza de espécies e um caráter não interativo, características comuns em comunidades parasitárias de répteis como hospedeiros.
The helminth community of the lizard Tropidurus torquatus from a rocky outcrop located in Minas Gerais state, southeast Brazil, was studied. Ninety two of the one hundred ten individuals examined (83,6%) harbored helminths. A total of five helminth species were found, tree nematodes: Physaloptera lutzi, Parapharyngodon sp. and Oswaldofilaria sp., one cestode species and one acanthocaphalan cystacanth not identified. Only nematode species had sufficient data to perform ecological analysis with Physaloptera lutzi showing the highest prevalence (67,3%) and mean intensity (4,86±4,85). Prevalence and intensity of infection between males and females hosts differed only for Oswaldofilaria sp., with males showing the highest values. Total and P. lutzi intensity of infection were different among males and females hosts, with males showing the highest values. The host body size was positively related to intensity of infection for all nematode species. Local seasonality had no influence in the helminth community structure. Host diet, sexual dimorphism and behavior (territorialism, forage strategy) represented important factors in the structuring of this parasite community. In general lines, the helminth community was species poor and non interactive, representing a typical community structure found in herps hosts.
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Besnard-Cochennec, Nathalie. "Bonamia ostreae, parasite de l'huître plate, Ostrea edulis : sa position taxonomique parmi les parasites du groupe "microcell" : analyses des interactions hôte-parasite chez plusieurs populations d'huître plates." La Rochelle, 2001. http://www.theses.fr/2001LAROS073.
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La Bonamiose, maladie due au protozaire Bonamia ostreae a été détectée en 1979 pour la première fois en Bretagne au cours d'épisodes de mortalité. Depuis, cette maladie s'est propagée à tous les centres ostréicoles français, puis européens. Une autre espèce, B. Sp. A été décrite en Nouvelle Zélande et en Australie. En outre, deux autres parasites ont été rapprochés du genre Bonamia. Il s'agit de Mikrocytos mackini qui affecte les huîtres creuses, Crassostrea gigas au Canada et M. Roughleyi qui affecte les huîtres sauvages en Australie, Saccostrea commercialis. Ces quatre parasites sont regroupés sous le nom " microcell ". Les caractérisations ultrastructurales et moléculaires de ces parasites ont été réalisées. Elles ont permis d'inclure les parasites B. Ostreae, B. Sp et M. Roughleyi dans le phylum des Haplosporidia. Une nouvelle espèce a été créée pour B. Sp. , B. Exitiosus. Des outils moléculaires de détection des genres B. Spp. Et M. Spp et d'identification d'espèces ont été mis au point (PCR, PCR-RFLP, Hybridation in situ). L'analyse en cytométrie en flux nous a permis de caractériser morphologiquement et fonctionnellement les effecteurs cellulaires des mécanismes de défense des huîtres plates, les hémocytes circulants. Trois types hémocytaires ont été décrits sur la base de leur taille et de leur granularité. La répartition hémocytaire indique que la population des cellules agranuleuses est majoritaire dans l'hémolymphe. Quatre lectines hétérologues ont permis de discriminer les populations granuleuses et agranuleuses. La mise au point de dosage d'activités cellulaires a permis d'évaluer pour chaque type cellulaire l'expression de six activités déterminantes dans les mécanismes post-phagocytaires. Ces activités sont majoritaires dans les granulocytes. Les grandes cellules agranuleuses et les petits hyalinocytes présentent les mêmes activités mais les taux d'expression sont plus faibles. Les résultats de phagocytose, in vitro, suggèrent que le parasite B. Ostreae intervient de manière active dans la phagocytose. Les résidus glycosylés présents sur la membrane cytoplasmique du parasite sont identiques à ceux présents à la surface des granulocytes suggérant un rôle important des lectines dans les phénomènes de reconnaissance et d'internalisation. Afin de rechercher d'éventuelles relations entre ces paramètres et la résistance à la Bonamiose, différentes populations d'huîtres sensibles et sélectionnées ont été comparées. L'étude a permis de mettre en évidence une corrélation entre l'expression des estérases des grandes cellules agranuleuses et la résistance à la Bonamiose. Ces paramètres pourront servir de critère de sélection dans les programmes d'amélioration génétique.
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Ibikounle, Moudachirou. "Les Schistosomoses au Bénin : épidémiologie et écologie des interactions hôte-parasite." Perpignan, 2006. http://www.theses.fr/2006PERP0706.
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Ce travail présente une étude épidémiologique et une étude des interactions hôte-parasite sur les schistosomoses au Bénin. Au plan épidémiologique, une synthèse bibliographique de l'état des travaux réalisés sur les schistosomoses dans l'espace de la Communauté Economique des Etats de l'Afrique de l'Ouest (CEDEAO) a été menée. Au Bénin, nos analyses épidémiologiques ont permis de confirmer l'existence de deux espèces de schistosomes humains : S. Haematobium et S. Mansoni sur les cinq signalées dans l'espace CEDEAO dans lequel le Bénin se situe (S. Haematobium, S. Mansoni, S. Guineensis, S. Bovis et S. Curassoni). La prévalence générale obtenue pour S. Haematobium est de 85% et celle de S. Mansoni est de 30%, avec l'existence de foyers de transmission mixtes. Les prospections malacologiques ont révélé la présence au Bénin d'au moins cinq espèces de mollusques potentiellement vectrices : B. Forskalii, B. Globosus et B. Truncatus, vectrices de S. Haematobium, B. Pfeifferi, vectrice de S. Mansoni et I. Exustus, mollusque exotique au Bénin, connu comme vecteur de S. Indicum, S. Spindale et S. Nasale en Asie du sud-est. Nous signalons la présence de I. Exustus pour la première fois au Bénin où ce mollusque semble être, pour le moment, passif dans la transmission des schistosomoses. Au plan de l'écologie des interactions mollusque-parasite, notre étude a montré que les différentes populations de S. Haematobium sont différemment compatibles avec trois des quatre groupes de mollusques Bulinus : le groupe africanus, le groupe forskalii et le groupe reticulatus alors que les différentes populations de S. Mansoni sont toutes également compatibles avec B. Pfeifferi. L'analyse de six traits d'histoire de vie, période prépatente, prévalence, production cercarienne chez le parasite et croissance, reproduction et survie des mollusques a été abordée avec cinq populations locales de schistosomes dont trois populations de S. Haematobium (Doh, Sô-Tchanhoué et Toho-Todougba) et deux populations de S. Mansoni (Kpinnou et Toho-Todougba) et a révélé que si les populations de S. Haematobium semblent être adaptées à un vecteur local, ce n'est pas le cas chez l'espèce S. Mansoni. Au plan de l'écologie des interactions vertébré-parasite, notre étude a révélé l'existence d'un rythme d'émission cercarienne horaire particulier, de type infradien, à la fois chez S. Haematobium et chez S. Mansoni. L'étude anthropique réalisée au niveau d'un des foyers de transmission (Toho-Todougba) où les deux espèces sont présentes a permis de constater une parfaite synergie entre la chronobiologie cercarienne et la dynamique des activités chez l'Homme : il pourrait s'agir d'une stratégie développée par le parasite pour maintenir ses rendez-vous avec son hôte naturel vertébréThis work presents an epidemiological and an ecological study of schistosomiasis in Benin. A synthesis of the epidemiological knowledge of schistosomiasis in the space of the Economic Community of West Africa States (ECOWAS) was carried out. Furthermore, in Benin, we confirmed the existence of the two human schistosomes : S. Haematobium and S. Mansoni on the five existing in the ECOWAS space in which Benin is located (S. Haematobium, S. Mansoni, S. Guineensis, S. Bovis and S. Curassoni). The prevalence obtained for S. Haematobium was 85% and that for S. Mansoni was 30%, and there was evidence for mixed human infections. We could find in Benin at least five potentially snail vector species : B. Forskalii, B. Globosus and B. Truncatus for S. Haematobium, B. Pfeifferi for S. Mansoni and I. Exustus, an exotic snail known to be the snail vector for S. Indicum, S. Spindale and S. Nasale in South-East Asia. I. Exustus is recorded for the first time in Benin in this work and no evidence of active transmission was made. The study of the snail-schistosome interactions showed that the different S. Haematobium populations were differently compatible with three of the four groups of Bulinus : the africanus group, the forskalii group and the reticulatus group and that the different S. Mansoni populations were equally compatible with B. Pfeifferi. The six life-history traits, parasite prepatent period, prevalence and cercarial production and snail growth, reproduction and survival were analyzed using five schistosome populations from Benin including three populations of S. Haematobium (Doh, Sô-Tchanhoué and Toho-Todougba) and two populations of S. Mansoni (Kpinnou and Toho-Todougba) and revealed that if the S. Haematobium populations seemed to be adapted to a local vector, this was not the case for the S. Mansoni populations. The study of the vertebrate-schistosome interactions revealed the existence of an infradian rhythm in the cercarial emissions of both S. Haematobium and S. Mansoni. The human behaviour, followed in one of the transmission sites (Toho-Todougba) where both schistosome species are present, was perfectly correlated with the schistosome chronobiology. This was interpreted in terms of adaptative strategy favouring the transmission of the parasite to its human host
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Fredensborg, Brian Lund, and n/a. "Ecological interactions between the trematode parasite Maritrema novaezealandensis (Microphallidae) and its intermediate hosts in the New Zealand intertidal soft-sediment community." University of Otago. Department of Zoology, 2005. http://adt.otago.ac.nz./public/adt-NZDU20060810.154001.
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Most, if not all, animals will at some stage in their lives encounter parasites. Some of the most widespread and abundant parasites belong to the Class Trematoda. Trematodes often have a substantial negative impact on individual intermediate host ecology. In this thesis, I investigate ecological and evolutionary consequences of the interaction between the microphallid trematode, Maritrema novaezealandensis, and its intermediate snail and crustacean hosts.
Parasites often show a heterogeneous spatial distribution pattern in natural animal host populations. In this study, factors determining the spatial distribution of larval trematodes in Zeacumantus subcarinatus were investigated at two spatial scales (within and among bays). The distribution of shorebird definitive hosts explained a significant amount of the variation in the distribution of trematodes among bays. However, within a bay, other factors override the effect of bird distribution.
The influence of larval trematodes on reproduction, survival and population density of Z. subcarinatus was investigated using laboratory and field studies. In the laboratory, it was found that larval trematodes induce castration and mortality of Z. subcarinatus. The field study revealed that the local prevalence of trematodes had a significant negative effect on population density of Z. subcarinatus.
Through castration, trematodes act as strong selective agents on snail host life history. The effect of trematodes on life history characteristics (reproductive effort, juvenile growth, size at maturity and susceptibility to trematode infections) were investigated among natural populations of Z subcarinatus. Reproductive effort was not higher for uninfected females from populations where the risk of becoming infected was high. However, offspring from those populations were significantly larger, and laboratory-reared juveniles grew significantly faster than conspecifics from other populations. In addition, size at maturity was negatively correlated with trematode prevalence across snail populations. Z. subcarinatus thus adapts to a high local risk of trematode infection by reaching maturity early, thereby increasing the chance of reproducing.
The influence of M. novaezealandensis on the survial of the amphipod host, Paracalliope novizealandiae was examined using experimental infections and field observations. The experimental infections demonstrated that parasite-induced mortality was intensity-dependent. The number of M. novaezealandensis per amphipod was too low to significantly induce host mortality in the field. However, the transmission strategy of this parasite allows it to affect host populations during weather conditions ideal for trematode transmission.
Trematode strategies in the second intermediate host are important to the understanding of host-parasite co-evolution and the evolution of parasite life cycles. In this study, potential density-dependent effects at the metacercarial stage on size and fecundity of in vitro adult M. novaezealandensis was examined in both experimentally infected P. novizealandiae and naturally infected Macrophthalmus hirtipes. For this purpose, a method to excyst and cultivate M. novaezealandensis metacercariae to an egg producing stage, was developed. Naturally infected M. hirtipes also harboured larval stages of three other helminths. Crowding effects in the two crustacean hosts were expressed as a decreased volume and smaller egg production of in vitro adult M. novaezealandensis. In addition, interspecific interactions among parasite species were observed in crab hosts.
The work in this thesis provides evidence that M. novaezealandensis significantly and negatively affect intermediate host ecology. The heterogeneous distribution of trematodes causes differential effects among host populations with subsequent effects on the life history of snail hosts. In addition, this study demonstrates that parasites interact within their second intermediate host with possible implications for the way parasites exploit their hosts.
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Badets, Mathieu. "Etude de la plasticité de développement de Polystoma gallieni, parasite de la rainette méridionale Hyla meridionalis : approches écologiques et moléculaires." Perpignan, 2008. http://www.theses.fr/2008PERP0937.
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La théorie synthétique de l'évolution attribue aux processus du développement une nouvelle dimension dans notre compréhension de l'histoire de la vie. Comme les forces de sélection naturelles et sexuelles, les forces du développement pourraient favoriser ou contraindre la diversification des espèces. Par le jeu d'une combinatoire génétique et par une étonnante capacité d'interaction avec l'environnement, le développement d'un individu pourrait donc être dévié dans sa trajectoire afin d'augmenter survie et reproduction. Ainsi, le développement qui permet l'expression d'une information (génétique) dans un système (écologique), serait le siège de compromis stratégiques touchant le cœur même du mot adaptation. Dans le cas des espèces ayant un mode de vie parasite, la stratégie de développement recouvre souvent celle de la transmission. D'un hôte à un autre au sein d'un écosystème, l'espèce parasite doit passer outre de nombreux filtres qui limitent sa capacité à se transmettre et à se reproduire. Que dire alors de cette surprenante plasticité dont fait preuve un parasite du genre Polystoma pour achever son cycle ? En fonction des caractéristiques de son hôte, le parasite alterne ses modes de développement pour profiter au mieux des opportunités qui lui sont offertes. Ce travail tente de décrire comment cette dualité stratégique parasite traduit l'importance des contraintes historiques et écologiques pour identifier les sources de pressions sélectives. Un questionnement intégratif du développement permet alors de rendre compte de la transmission au sein d'un écosystème temporaire et hétérogèneWithin the synthetic theory of evolution, the processes and patterns of development highlight a new dimension into our understanding of the history of life. Like the natural and sexual forces of selection, development could promote or constrain the diversification of species. Through a combination of genetic modules and an amazing ability to interact with the environment, the development of an individual could be deflected in its trajectory to increase survival and reproduction. Therefore development which allows the expression of information (genetic) in a (ecological) system, would involve strategic trade-off revealing fine tuned adaptations. When species present a parasitic lifestyle, developmental strategy often includes this of transmission. Going from host to host within an ecosystem, the parasite has to bypass many filters that limit its ability to transmit and reproduce. What about the surprising plasticity triggered by a parasite of the genus Polystoma to complete its cycle? Depending on the characteristics of its host, the parasite alternates its developmental pathways in regards of transmission opportunities. This work shade lights on the importance of historical and ecological constraints behind developmental mechanisms and tempts to identify the source of selective pressures. Sole an integrative approach of the parasite development can report how the transmission may occur within a temporary and heterogeneous ecosystem
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Dubois, Jacques. "Phylogénie moléculaire et morphologique des Pimplinae (Hymenoptera, Ichneumonidae) parasites d'araignées : scénarios évolutifs du mode de parasitisme." Paris, Muséum national d'histoire naturelle, 2005. http://www.theses.fr/2005MNHN0063.
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Les Pimplinae sont une des sous-familles d’Ichneumonidae dont les modalités de relation hôtes-parasitoïdes sont les plus diversifiées et dont la biologie est parmi les mieux connues. Des hypothèses phylogénétiques ayant déjà été établies sur des bases morphologiques pour la sous-famille, nous avons (1) confirmé ces hypothèses à l’échelle générique à partir de données moléculaires originales basées sur l‘étude des ADNr 28S,16S et du CO1; (2) approfondi les relations de parenté au sein du groupe de genres Polysphincta ; (3) établi des hypothèses sur l’évolution du parasitisme au sein du groupe. Une phylogénie morphologique robuste du groupe de genres Polysphincta (parasitoïdes d’araignées) a permis de délimiter 21 genres dont trois nouveaux. L’inclusion dans la matrice de caractères biologiques a permis de retracer l’histoire évolutive du groupe à travers l’évolution du mode de parasitisme et d’autres traits comportementaux liés à la larve et à son coconPimplinae are the subfamily whose parasitism patterns are the most diversified and biology one of the best known within the Ichneumonidae. Hypotheses on Pimplinae phylogeny being already established from morphological data, this work aimed at (1) supplying original molecular data, based on 28S and 16S rDNAs and CO1 analyses, in order to test the morphological hypotheses at a generic level; (2) detailing relationships within the Polysphincta genus group ; (3) establishing hypotheses about the evolution of parasitism patterns within this group. The study of the Polysphincta genus group, based on a morphological phylogeny, led to the redefinition of 21 genera, among which 3 were new. The subsequent inclusion of biological characters in the matrix enabled to retrace the evolutionary history of this group through the evolution of parasitism patterns and other behavioural traits of the larva and its cocoon
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Le, Brun Nathalie. "Spécificité des relations hôtes-parasites : le modèle Cyprinidae-Diplozoon." Montpellier 2, 1988. http://www.theses.fr/1988MON20055.
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La spécificité parasitaire est abordée à travers les modèles fournis par 4 espèces du genre Diplozoon, parasite branchial de Cypirindae. Plusieurs populations de Diplozoon sont étudiées et comparées dans le sud de la France et en Suisse (lac de Neuchatel)
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Tabouret, Guillaume. "Oestrus ovis(linné 1761) [Diptera : oestridae] chez les ovins : application à la caractérisation des tumeurs mammaires." Toulouse 3, 2001. http://www.theses.fr/2001TOU30021.
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Nno, Mabiala Alix Dania. "Mécanismes et agents de la virulence chez les parasitoïdes hyménoptères Braconides du genre Asobara : le cas particulier d'A. Japonica." Amiens, 2009. http://www.theses.fr/2009AMIE0109.
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Le succès reproducteur d'un parasitoïde dépend en grande partie de sa capacité à infester son hôte et à s’y développer. Les parasites sont généralement capables d’éviter, de neutraliser ou de détourner la réponse immunitaire innée de leur hôte. Le processus le plus répandu est la production de facteurs immunosuppresseurs bloquant cette réponse, ou de facteurs toxiques provoquant la mort des cellules de défense. Ce travail de thèse porte sur la comparaison des mécanismes et des agents de la virulence chez les Hyménoptères braconides du genre Asobara. L’étude a porté sur deux espèces, A. Japonica et A. Persimilis, parasitoïdes de larves de D. Melanogaster. Les résultats ont été comparés à ceux précédemment décrits chez A. Tabida et A. Citri. Nous avons montré que la stratégie d’immunosuppression développée par l’espèce A. Japonica lui permet d’échapper dans 100 % des cas à l’encapsulement par les larves de D. Melanogaster. La stratégie de virulence de ce parasitoïde est basée sur une altération complète de l’organe hématopoïétique, ce qui se traduit par une incapacité de la larve hôte à amplifier sa population hémocytaire, toutes catégories hémocytaires confondues. En revanche, les œufs d’A. Persimilis se font encapsuler dans 13% des cas par les larves de D. Melanogaster. Ce parasitoïde affecte également l’organe hématopoïétique mais de façon plus limitée. Chez les larves hôtes, la prolifération des seuls lamellocytes semble être affectée suite à l’infestation par A. Persimilis. La recherche des facteurs responsables de la virulence a conduit à la démonstration d’un effet paralysant puis mortel des venins d’A. Japonica et d’A. Persimilis. De façon remarquable, cet effet peut-être régulé par l’injection d’extraits ovariens de ces parasitoïdes. Les sécrétions venimeuses et ovariennes des femelles d’A. Japonica et d’A. Persimilis seraient donc indispensables au succès du développement parasitaire. L’identification des composés venimeux a été initiée chez A. Japonica, espèce chez laquelle les effets toxiques et immunosuppresseurs sont les plus marqués. On s’est aussi interrogé sur la convergence, ou non, des stratégies et agents développés par les Hyménoptères parasitoïdes pour immuno-déprimer leur hôte. On constate qu’au sein de la communauté des parasitoïdes larvaires de drosophiles, il existe une hétérogénéité des mécanismes et agents immunosuppresseurs, et que cette hétérogénéité dépasse le cadre du genre AsobaraSuccess of parasitoids depends on their ability to infest a host and to complete their development. Endophagous parasites are able to avoid, neutralize or deflect the innate immune response of encapsulation by the hemocytes of their host. The most common mechanism is the production of either immunosuppressive factors blocking this response or of toxic factors causing the death of the hemocytic cells. In this thesis, we compared the mechanisms and agents of the virulence in Hymenoptera braconid species of the genus Asobara. The two species A. Japonica and A. Persimilis, parasitoids of Drosophila larvae, were studied. Results were compared to those previously obtained in A. Tabida and A. Citri. We here show that A. Japonica strategy of immunosuppression permits the parasitoid to successfully escape encapsulation in 100% of the D. Melanogaster parasitized hosts. The virulence strategy of this species is based on the overall destruction of the host’s hematopoietic organ, associated with the inability of the larval host to amplify any hemocyte type. Differently, A. Persimilis eggs are encapsulated in 13% of D. Melanogaster host larvae. This parasitoid species affects, too, the host hematopoietic organ, although this effect is limited compared to A. Japonica. Lamellocytes, which number does not increase post-parasitization, seem to be the only host’s hemocyte type which is affected by A. Persimilis. The analysis of the factors responsible of the parasitoids virulence permitted to demonstrate a paralyzing then deadly effect of the venoms from both A. Japonica and A. Persimilis. Surprisingly, the deadly effect is regulated by the female wasps’ ovarian fluids. Therefore, both venom and ovarian fluids of the female wasps appear to be required for the successful development of the parasitoids. The identification of the wasps’ venom components has been initiated in A. Japonica, the species presenting the most toxic and immunosuppressive effect. We ask the question of the possible convergence between the strategies and agents developed by hymenopteran parasitoids to immunodepress their hosts. It appears that within the community of Drosophila larval parasitoids, there is some heterogeneity of the mechanisms and agents of immunosuppression, and that this heterogeneity is beyond the scope of the Asobara genus
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Davies, Charlotte Mary. "Snail-schistosome interactions and the evolution of virulence." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343421.
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Kelly, Colleen Kay. "Host use and foraging in the parasitic plant Cuscuta subinclusa." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184543.
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Foraging theory predicts active responses by organisms upon encounter with a resource, as opposed to the passive responses of differential survivorship and growth. Stems of the parasitic plant Cuscuta subinclusa invest in resource acquisition (coil) relative to host quality in a way predicted by the marginal value theorem (MVT) in that: (1) stem coiling, the necessary antecedent and determinant of resource uptake, precedes exploitation of host materials; and (2) mean coiling on a host species is proportional to: (a) mean growth/haustorium, (b) mean biomass accumulation over the season, and (c) mean parasite growth/host individual. Coiling is correlated with growth/host individual for the 5 native host species examined, but not when a non-native species is added to the model, suggesting coiling response is a result of natural selection. Preliminary evidence indicates that coiling in C. subinclusa is induced by host bark chemicals. Resource-poor stems of C. subinclusa are more likely to coil, and coil more, than resource-rich stems, thus nutritional state of the parasite as well as host value affects foraging responses. Evidence from other experiments suggests that the costs of growth, or "search costs", may affect host acceptability. When water is readily available, transplanted C. subinclusa stems are less likely to coil on branches of Platanus racemosa. During the dry season, when cellular expansion is difficult, all p. racemosa branches were coiled upon. Large parasites are more likely to over-winter and set seed a second season, and parasites that start from over-wintered tissue are significantly larger at flowering than are those that have started from seed. Seed set is correlated with parasite size, thus linking foraging response and fitness of the plant. C. subinclusa's foraging response does not, however, predict population level patterns of host use. The principal determinant of host use by C. subinclusa is average proximity of a species to Malosma laurina. Parasite individuals infest many host species each season, but initially establish, set most seed, and over-winter only on M. laurina. Individual response of C. subinclusa contributes to the model of host use only after proximity to M. laurina is accounted for, suggesting that mechanisms maximizing exploitation of a host take effect after contact between host and parasite.
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McKay, Derek Mark. "Aspects of the neurobiology of two parasitic platyhelminths, with observations on host-parasite interactions." Thesis, Queen's University Belfast, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335561.
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Pollok, Richard. "Cryptosporidium parvum : host-parasite interactions." Thesis, Queen Mary, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402442.
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Herbert, Julian Richard. "Stochastic processes for parasite dynamics." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368164.
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Watson, Andrew Keith. "Characterising microsporidian host-parasite interactions." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3504.
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Microsporidia are an enormously successful group of obligate intracellular fungal parasites that infect most eukaryotes including humans. In my thesis I have analysed and compared microsporidian genomes to identify which genes have been conserved, and which lost, during the transition of the group to parasitism, sequenced the transcriptome of a mixed infection of Trachipleistophora hominis in a rabbit kidney cell line, and provided a description of the T. hominis intracellular lifecycle. My results demonstrate that microsporidian genome evolution is extremely dynamic; with huge loss of genes in the microsporidian common ancestor balanced by group and lineage-specific gene family expansion and innovation. Genes that are conserved among microsporidians are generally expressed at higher than average levels in the transcriptome of T. hominis. Lineage-specific genes show greater variation in expression, but some are very highly expressed suggesting that they play important roles in T. hominis biology. The transcriptomics data for T. hominis confirmed that it contains one of the largest microsporidian genomes in terms of gene content and also identified previously unannotated genes, some of which may have important roles in the parasite. Detailed analysis of my gene expression data demonstrated that differential expression of duplicate genes is a general feature of T. hominis gene families, including nucleotide transport proteins that are already known to have important roles in the microsporidian lifestyle. A method for partially synchronising the T. hominis infection was established and used to investigate the development of the infectious cycle using light microscopy and antibodies to T. hominis proteins. My observations suggest that the infection proceeds in a reproducible and predictable pattern under the experimental conditions used; providing a tool for future detailed study of how T. hominis infects and exploits eukaryotic host cells.
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Hallowell-Evans, Cara Louise. "Parasite control on thoroughbred studs." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3022893/.
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Gastrointestinal parasite infections impact on the health and welfare of Thoroughbreds (TB). The parasites of concern include the strongyles; cyathostomins and Strongylus vulgaris, Parascaris equorum and Anoplocephala perfoliata. In addition, there is increasing recognition of liver fluke infections in horses. Life-long parasite control is needed and use of anthelmintic drugs is the major approach, but decades of intensive anthelmintic usage has promoted widespread resistance particularly in cyathostomins and Parascaris equorum. Intensive anthelmintic usage is defined as the administration of an anthelmintic drug at set intervals, based on the original egg reappearance period (ERP) of the pioneer product, with the aim of egg output suppression; following the recognition and widespread nature of anthelmintic resistance targeted selective treatment regimens are now being advocated. Targeted selective treatment is defined by the American Association of Equine Practitioners (AAEP) as basing treatments during high transmission periods on diagnostic testing and identification of high egg shedding individuals in order to reduce pasture contamination while leaving a parasitic population in refugia, due to the current limitations in detection whole herd moxidectin and praziquantel treatments are still advocated annually as a minimum, with frequency dependent on a risk analysis and utilisation of available assays. The aim of this project was to identify parasite control practices on UK TB studs, determine drug efficacy on a subset of TB studs and evaluate the diagnostic potential of faecal diagnostic tests. Faecal diagnostic tests for F. hepatica and A. perfoliata were examined. A McMaster-based short method for F. hepatica was applied to known positive donkey (n=18) and horse (n=1) samples which were simultaneously evaluated with the standard sedimentation method. Mean egg per gram (epg) count was 21.0epg (0.2-138epg) and 31.0epg (0.4-202epg) for the short method and standard sedimentation, respectively. The centrifugal flotation (CF) method was investigated for detection of A. perfoliata eggs and compared to the validated double sugar flotation (DCF) test. In total 140 samples were tested. Of these, 25.7% (±7.2%, n=36/140) tested positive using CF and 22.1% (±6.9%, n=31/140) using DCF. Nine TB studs have undergone drug efficacy testing based on their anthelmintic use, control strategies and clinical disease concerns, mebendazole was tested on one stud, pyrantel on five studs; ivermectin on three and moxidectin on two. Tests were conducted for adults and youngstock independantly. The CF faecal egg count (FEC), sensitive to 1epg, was used to detect strongyle-type, Parascaris spp and A. perfoliata eggs. On studs where >10 animals showed > 50epg (strongyle), faecal egg count reduction tests (FECRT) were performed to determine resistance status. ERP was defined as when group arithmetic mean FEC post-treatment exceeded 10% of group FEC arithmetic mean pre-treatment. Larval culture and morphological identification of strongyle third-stage larvae were also performed. On stud B, youngstock [YS] (n=7) PYR efficacy was 98.5% (97.9-99.0%), ERP = 3 weeks, and 93.2% (91.9-94.3%) in mares (n=8), ERP = 4 weeks; stud D only YS (n=31) showed resistance to PYR (reduction = 58.8% (57.6-60.0%)), sensitivity to IVM (100.0% (99.9-100.0%)) but borderline efficacy to MOX (94.5% (93.9-95.1%); ERP 4 weeks); stud F showed PYR resistance (n=23 YS, n=13 mares) with 0.1% (0.0-0.7%) and 69.5% (67.0-71.8%) reductions, IVM and MOX efficacy were 100.0% (99.9-100.0%) but ERP shortened to 6 weeks (IVM) and 8 weeks (MOX) in YS; stud G YS showed PYR resistance (n=18, 67.5% (64.9-69.9%) reduction). One stud (stud E) was referred to the project due to high levels of tapeworm-related disease in broodmares (~60-70% of mares affected per year). All stock were tested using the CF and DCF faecal methods and University of Liverpool (UofL) serum ELISA (adults, n=86; YS, n=64). For adult stock 74.4% (±9.7%, n=58/78) recorded negative A. perfoliata FEC using the CF method and 79.5% (±9.0%, n=62/78) using the DCF; for YS (n=48) 75.4% (±10.8%, n=46/61) were recorded as negative by both CF and DCF. Over the study period February 2015 to Jul 2016 94.7% (±3.6%, n=142/150) of all samples tested by ELISA were reported to have a moderate to high infection intensity. Highest proportion showing high infection intensity (O.D. > 0.201) on ELISA occurred in June 2015 (100% of adults and YS). Despite intensive three monthly praziquantel treatments from February to September 2015, no apparent decline in O.D. values was noted for either cohort, but FEC analysis revealed fewer horses were FEC positive over time. A questionnaire survey was conducted with, questionnaires distributed to active studs (n=184) with the option to complete by post, online or telephone. Response rate was 39 studs (21.2%). FEC had been performed by 80.6% (±12.9%, n=28/36) but 17.1% (±12.2%, n=6/36) only used FEC at suspicion of disease. 97.1% (±5.7%, n=33/34) were very concerned about resistance to worming drugs, despite this 40.0% (±16.2%, n=14/35) of studs use intensive regimens with only 27.3% (±14.6%, n=10/36) having performed a FECRT. Faeces were only removed from pasture on 53.9% (±15.9%, n=20/38) of studs with harrowing being performed annually on 23 (59.0% ±15.4%, n=23/39) 60.0% (±16.2%, n=21/35) of studs use targeted selective management, however, not all of these studs correctly defined the principle of targeted selective treatment so true level of implementation is unknown. This work has provided vital information to TB studs about drug efficacy. By evaluating current diagnostic tests for their ability to detect infection with other parasites it raises the possibility of a holistic and time-efficient approach to targeted selective parasite control. It has highlighted the crucial role diagnostics have in detecting parasitic infection and parasite-associated disease and has identified current practice on stud. Together these findings can be used to better support targeted selective treatment of parasites in TB horses and improve parasite control on studs.
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Caldevilla, Sonia. "Demodex folliculorum : parasite de l'homme." Paris 5, 1999. http://www.theses.fr/1999PA05P094.
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Ali, K. S. M. "Immunity to Leishmania mexicana parasite." Thesis, Nottingham Trent University, 2014. http://irep.ntu.ac.uk/id/eprint/156/.
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Background: Cutaneous Leishmaniasis caused by the Leishmania mexicana complex is associated with unpleasant or disfiguring lesions, for which there only limited treatment options. The life cycle of L. mexicana consists of two stages which involve different immune evasion mechanisms: promastigote and amastigote. Understanding parasitic interactions with host cells and developing a protective vaccine could improve the management and treatment of the disease. Aims: • To construct and compare the immunogenicity of 3 Leishmania genes in 3 different plasmids. • Study the effect of long term in vitro culture on the virulency of L. mexicana and its interaction with host cells. • To analyse the influence of Leishmania infection on MHC class I expression by susceptible human cell lines (U937 macrophages, U937 and MonoMac-6 monocytes), and Toll-like receptor, cytokines and chemokines gene expression profiles. Methodology: Three Leishmania genes (L. mexicana GP63, L. donovani centrin1 and L. donovani centrin3) were cloned into three plasmids (pcRT7/CT-TOPO; VR1012; and pcDNA3.1/Hygro(-)). The immunogenicity of the prepared DNA constructs and their empty counterparts was assessed in Balb/c mice using gene gun immunisation method. An in vivo model of attenuated L. mexicana was produced by growing the parasite in vitro for up to passage 20, and testing the infectivity of these parasites in vivo and in vitro. The influence of infecting target cells with virulent and avirulent L. mexicana at different growth stages on MHC class I expression was determined by flow cytometry. Gene expression profiles were determined by qPCR analysis of extracted mRNA. Results: All tested Leishmania DNA constructs were highly immunogenic compared to the controls, as assessed using ELISPOT and cell proliferation assays. A novel survival assay developed in this study illustrated that macrophages derived from immunised mice were resistant to Leishmania infection. The parasite at passage 1 was highly infectious (virulent), but this progressively decreased to be completely avirulent at passage 20. This was associated with a significant down regulation of virulence-associated genes (GP63, LPG2, CPC, CPB2, CPB2.8, CHT1, LACK and LDCEN3) at passage 20, and was also accompanied by morphological changes. The avirulent parasite was unable to transform to the pathogenic amastigote stage in infected target cells. The gene expression profile of toll-like receptors (TLR-1, TLR-2, TLR-4, and TLR-9), cytokines (IL-1, IL-6, IL-10, IL-12β, TNF-α, and TGF-β), and chemokines (CCL-1, CCL-2, CCL-3, CCL-4, CCL-5, and CCL-22) in target cells was were induced and inhibited according to the virulence status of the parasite. Similar and significant down regulation of MHC class 1 was induced by infection of target cells for 24 hours with both virulent and avirulent L. mexicana parasite, however after 48 hours of infection only cells infected with avirulent but not virulent parasite have significantly restored their MHC class I expression. Conclusions: Since no differences in the immunogenicity of the three plasmids encoding the same Leishmania gene were observed, immunogenicity is not dependent on the plasmid type. The failure of the avirulent L. mexicana parasite to infect Balb/c mice, and its inability to produce the pathogenic amastigote stage in vitro suggests that it might have potential as a vaccine candidate. This was also supported by the up regulation of Th2 mediators following the infection with virulent compared avirulent parasites. The level of MHC class I down regulation was dependent on parasite growth stage, virulency and infection dose.
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Morga, Benjamin. "Etude des interactions hôte/parasite chez l'huître plate Ostrea edulis et son parasite Bonamia ostreae." Phd thesis, Université de La Rochelle, 2010. http://tel.archives-ouvertes.fr/tel-00618480.
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L'histoire de l'ostréiculture française met en évidence la fragilité de cette production face à la surexploitation des stocks et l'apparition de maladies. En particulier, la production d'huître plate, Ostrea edulis, a fortement diminué suite à l'apparition de deux maladies parasitaires dont la bonamiose. Les moyens de lutte contre la bonamiose sont relativement restreints. Ils sont essentiellement basés sur la surveillance de la santé des huîtres afin de limiter la dissémination et la propagation de la maladie. Cependant l'utilisation de modèles prédictifs de l'évolution de la maladie en zone infectée permettrait d'optimiser la gestion des stocks et minimiser l'impact des agents pathogènes. De plus, le développement d'animaux résistants à l'infection pourrait permettre de relancer cette production. Ces différentes approches nécessitent des outils diagnostiques adaptés, une bonne connaissance du cycle de vie de l'agent pathogène, et, plus particulièrement des interactions du parasite avec son hôte. Dans ce contexte, l'objectif principal du travail de thèse proposé est de comprendre les interactions entre l'huître plate Ostrea edulis et son parasite Bonamia ostreae, et, plus particulièrement les bases moléculaires de la résistance au parasite. Dans un premier temps, la réalisation d'une banque soustractive d'ADNc a permis d'identifier des ESTs différentiellement exprimées chez des hémocytes en réponse au parasite. L'expression de certains gènes dont une galectine a été mesurée en PCR en temps réel dans le contexte d'infections in vitro. En complément, la réponse cellulaire a été étudiée par cytométrie en flux et l'infection contrôlée en microscopie. Ces expériences ont montré une multiplication parasitaire dans les hémocytes au cours du temps associée à une diminution de la production d'EOR et d'estérases. Dans un second temps, il a été entrepris une étude comparative entre une population d'huîtres plates résistantes à la bonamiose et une population naturelle. Les résultats obtenus tendent à montrer qu'une modulation de l'apoptose et une diminution de la phagocytose seraient impliquées dans les mécanismes liés à la résistance à la bonamiose. Ce travail est le premier à étudier la réponse des hémocytes d'huîtres plates à une infection par le parasite Bonamia ostreae au niveau cellulaire et moléculaire.
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Brewster, Bernice. "Aquatic Parasite Information : a database on parasites of freshwater and brackish fish in the United Kingdom." Thesis, Kingston University, 2016. http://eprints.kingston.ac.uk/39278/.
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A checklist of parasites of freshwater fish in the UK is an important source of information concerning hosts and their distribution for all aspects of scientific research. An interactive, electronic, web-based databse, Aquatic Parasite Information has been designed, incorporating all freshwater and brackish species of fish, parasites, taxonomy, synonyms, authors and associated hosts, together with records for their distribution. One of the key features of Aquatic Parasite Information is this checklist can be updated. Interrogation of Aquatic Parastie Information has revealed that some parasites of freshwater and brackish species of fish, such as the unicellular groups or those metzoans that are difficult to identify using morphological characters, are under reported. Aquatic Parasite Information identified the monogenean family Dactylogyridae and the cestodes infecting UK freshwater fish as under-represented groups, owing to the difficulties identifying them morphologically. Both the Dactylogyridae and cestodes have implications for pathology, outbreaks of disease and morbidity in freshwater fish in the UK, therefore accurate identification is critical. Studies were undertaken using both standard morphological techniques of histology and molecular techniques to identify dactylogyrid species and tapeworms commonly found parasitizing fish in the UK. Morphological studies demonstrated that histological processes could lead to distortion of the specimins and permanent mounting may affect the orientation which may obscure vital characteristics. Moleculr techniques were successfully employed using ITS1 for the Dactylogyridae and cox1 and r28s for the cestodes, to demonstrate genetic variability for the interspecific identification of species. Histology, scanning electron microscopy and molecular techniques have also identified an Atractolytocestus sp. tapeworm, parasitizing carp in the UK, as a potentially new species. Analysis of parasite records extracted from Aquatic Parasite Information has implicated freshwater fishery management policies as impacting on the dissemination and distribution of parasites, resulting in the spread of some species and decline of others.
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Lester, Hannah. "Anthelmintic resistance in equine parasites : an epidemiological approach to build a framework for sustainable parasite control." Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2029559/.
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Faecal egg count (FEC) directed targeted anthelmintic treatment programmes and regular efficacy testing using the faecal egg count reduction test (FECRT) have been advocated to support evidence-based helminth control in horses. One major hurdle to their widespread application is that horse owners/managers and those that prescribe anthelmintics may have insufficient knowledge on which to base evidence-based protocols. The ultimate aim of this study was to create a framework for a decision support system (DSS) to support evidence-based helminth control in horses. To create the framework, the diagnostic performance of FEC and FECRT methodologies were evaluated. In addition, the efficacy of the three licensed anthelmintic classes was tested in several equine populations. The prevalence and distribution of helminths was determined in these populations, and an analysis undertaken to investigate factors associated with different levels of strongyle egg shedding in individuals. The consistency of egg shedding patterns in individuals over time was evaluated and the resource implications of following a FEC directed targeted treatment investigated. The FEC analysis findings support the rationale of FEC directed targeted anthelmintic treatments in horses to reduce treatment frequency in order to mitigate the impact of anthelmintic resistance. Moreover, the results show that such a strategy may be cost effective. The efficacy studies revealed that the macrocyclic lactone anthelmintics were highly effective in reducing strongyle egg output at two weeks after treatment, but further studies are required to analyse the strongyle egg reappearance period after treatment with these anthelmintics. In summary, this study validates the use of FEC directed treatment protocols in the field and the next step will be to use the derived information to design user-friendly online support tools.
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Davis, Richard Elliot. "Neutrophil responses to infection with leishmania parasites: MHC class II-expression and parasite life-stage interactions." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/2200.
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The vector-borne protozoan Leishmania spp. cause the spectrum of disease known as leishmaniasis in human and animal hosts. The most common manifestations of leishmaniasis are the chronic, ulcerative skin disease cutaneous leishmaniasis (CL), and the more serious visceral leishmaniasis (VL) in which parasites take up residence in internal organs, causing death if not treated. The role of neutrophils (PMNs) in the immune response to CL and VL is unclear. It is s generally thought that PMNs are only a short-lived effector cell, and have been disregarded as playing a role in chronic Leishmania spp. infection. As both CL and VL are diseases characterized by increased inflammatory immune mediators, we hypothesized that PMNs from human or animal models of chronic leishmaniasis would display different properties from PMNs from healthy controls. We found in a subset of CL and VL patients circulating PMNs expressing HLA-DR, the human form of MHC class II, a molecule thought to be restricted primarily to professional antigen cells. When we examined PMNs recruited to CL skin lesions in human patients, or similar lesions in experimental murine model of CL, we found significantly increased MHC class II+ PMNs. Circulating HLA-DR+ PMNs also expressed the co-stimulatory molecules CD80, CD86 and CD40. While this suggested an antigen-presenting cell-like phenotype by these HLA-DR+ PMNs, compared to conventional HLA-DR- PMNs, HLA-DR+ PMNs showed not only a neutrophil-like appearance and function, but in fact increased activation, degranulation, intracellular MPO and phagocytosis of parasites and zymosan particles. Incubation of healthy control whole blood with inflammatory cytokines resulted in increased HLA-DR+ PMNs and the presence of hladrb1 mRNA, suggesting a connection between neutrophil “priming” and upregulation of HLA-DR.
In addition to HLA-DR+ PMNs in CL patients, we also identified the presence of so-called “low-density” neutrophils (LD-PMNs). These neutrophils, which are enriched in low-density fractions following centrifugation of blood over a density gradient, are reported in numerous disease states, including cancer, HIV, and systemic lupus erythematosus. In some disease states, LD-PMN are reported to be immunosuppressive toward T cell activation and proliferation. However, LD-PMNs from leishmaniasis patients showed no evidence of immunosuppression. Additionally, we found that LD-PMNs show significantly increased surface expression of MHC class II, suggesting a heretofore unappreciated connection between these atypical neutrophil phenotypes. We also investigated the in vitro interactions with different Leishmania infantum life-stages, both those that cause acute infection (promastigotes) and amastigotes, which are found during chronic stages of the disease. We found that PMNs are readily infected by all L. infantum life-stages, but that amastigotes may have different methods of interacting with PMN surface receptors and are better equipped to avoid PMN anti-microbial responses.
These data suggest that circulating PMNs in chronic leishmaniasis may have unique phenotypes and interact differently with the Leishmania spp. life-cycle present during chronic infection. Further investigation of the role of PMNs and atypical PMN phenotypes in chronic disease may help identify new immunomodulatory roles for this cell type.
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Bouchut, Anne. "La compatibilité dans l’interaction Biomphalaria glabrata/Echinostoma caproni : recherche de gènes candidats." Montpellier 2, 2007. http://www.theses.fr/2007MON20009.
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Les interactions hôte-parasite entre mollusques et trématodes se caractérisent par un polymorphisme de compatibilité qui se manifeste par la présence de couples compatibles (hôte susceptible et/ou parasite virulent) et de couples incompatibles (hôte résistant et/ou parasite avirulent) en populations naturelles. Afin d’appréhender les déterminants moléculaires responsables de cette compatibilité différentielle entre le mollusque Biomphalaria glabrata et le trématode parasite Echinostoma caproni, plusieurs études moléculaires comparatives ont été réalisées sur deux souches de B. Glabrata, susceptible et résistante à E. Caproni. Des travaux antérieurs ayant mis en évidence des différences plasmatiques et hémocytaires entre ces souches, nos approches moléculaires ont été menées dans un premier temps sur ces compartiments biologiques. Nous avons développé (i) une approche protéomique pour comparer le contenu protéique de leur plasma et hémocytes, (ii) une approche transcriptomique plus ciblée sur les transcrits correspondant à des gènes potentiellement impliqués dans les processus d’adhérence dans les hémocytes. Enfin, les résultats obtenus nous ont conduits à réaliser une approche transcriptomique plus globale par banques soustractives sur mollusques entiers de façon à identifier d’autres gènes exprimés par d’autres compartiments ou tissus. Ces travaux nous ont permis d’identifier toute une série de candidats différentiellement représentés entre mollusques susceptibles et résistants et potentiellement impliqués dans les différences de compatibilité entre souches. Parmi eux, on trouve des gènes potentiellement impliqués dans (i) la reconnaissance du parasite et les voies de signalisation (Calcium binding Protein, glycosidases et C-type lectin), (ii) la mobilité et l’adhérence (protéines à domaines Von Willebrand, cadhérine, dermatopontines et protéine de filament intermédiaire), (iii) la régulation de l’expression des gènes (histone H4), ou encore (iv) des gènes codant les effecteurs de la réponse immunitaire (inhibiteurs de protéases, protéases et aplysianin). Mots-clés : Biomphalaria glabrata, Echinostoma caproni, interaction hôte-parasite, compatibilité, susceptibilité-résistance, invertébré, approches moléculaires comparativesHost/parasite interactions involving snails and trematodes showed a strong polymorphism for compatibility. This polymorphism leads to the existence of susceptible and resistant snails to the parasite in the same host population. In order to understand the molecular determinants responsible for the differential compatibility of the mollusc Biomphalaria glabrata for the trematode Echinostoma caproni, we developed several molecular approaches to compare two host strains, one susceptible and one resistant to E. Caproni. Previous studies provided evidence that differences exist between susceptible and resistant hosts humoral factors and that constitutive differences exist between susceptible and resistant hemocytes that concern their adhesion abilities. To further investigate the molecular basis of differences pointed out, we carried out (i) a comprehensive proteomic approach to compare protein content extracted from plasma or hemocytes, (ii) a transcriptomic approach, well targeted on genes potentially involved in adhesion processes in hemocytes and (iii) finally, the results we obtained led us to perform a complementary transcriptomic approach by constructing subtractive libraries on entire snails in order to identify other cellular compartments or tissues potentially involved in susceptibility-resistance processes. These studies revealed several candidate genes differentially expressed between susceptible and resistant snails and potentially implied in different functions that could participate in compatibility processes: (i) Parasite recognition and signalling pathways (Calcium binding Protein, glycolytic enzymes and C-type lectin) ; (ii) Mobility and adhesion (proteins containing Von Willebrand domains, cadherin, dermatopontins and intermediate filament protein) ; (iii) Immune defence effectors (protease inhibitors, proteases and aplysianin) and (iv) Regulation of gene expression (histone H4). Keywords: Biomphalaria glabrata, Echinostoma caproni, host-parasite interaction, compatibility, susceptibility-resistance, invertebrate, comparative molecular approaches
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Khalaf, Sahira. "Parasite epidemiological and pollution/parasite interaction studies on sticklebacks (Gasterosteus aculeatus L.) from the River Wandle." Thesis, King's College London (University of London), 1998. https://kclpure.kcl.ac.uk/portal/en/theses/parasite-epidemiological-and-pollutionparasite-interaction-studies-on-sticklebacks-gasterosteus-aculeatus-l-from-the-river-wandle(86b59e83-fa4d-4a7c-8a08-87112517c39b).html.
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White, Emily Claire. "Infection by the gastrointestinal parasite Trichuris muris : defining the microbiota of the parasite and the host." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/infection-by-the-gastrointestinal-parasite-trichuris-muris-defining-the-microbiota-of-the-parasite-and-the-host(e29ed75d-014d-4e36-87ed-a6db82845511).html.
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Intestinal dwelling parasites live in close association with the complex microbiota that inhabit our intestinal tracts. The intestinal helminth, Trichuris muris, depends on these bacteria for egg hatching and successful establishment of infection within the epithelium of the caecum and colon. Infection causes significant alterations to the host intestinal microbiota, including a decrease in bacterial diversity and shifts in proportions of certain bacterial groups. This is accompanied by a decrease in Foxp3+ regulatory T cells and changes to the metabolic potential of the host microbiota, consequently impacting host health. However, the factor(s) driving these changes and the existence and role of its own intestinal microbiota is unknown. Infection of C57BL/6 and immunodeficient SCID mice with a high dose (~ 200 embryonated eggs) and a low dose (~ 20 embryonated eggs) of T. muris was used to determine the impact of worm burden and the adaptive immune system on the host intestinal microbiota, in comparison to naïve controls. Microbiota analysis was performed by 16S rRNA gene denaturing gradient gel electrophoresis (DGGE) and Illumina sequencing. This revealed that infection-induced microbiota changes were dose dependent and high level infection caused an increase in the Bacteroidaceae and Enterobacteriaceae families, independently of the host adaptive immune system. Development of a surface sterilisation protocol enabled the internal T. muris microbiota to be analysed by 16S rRNA gene DGGE and fluorescence in situ hybridisation (FISH). The resulting data indicated that T. muris requires its own diverse intestinal microbiota that is derived from, but distinct to, that of its host. A core microbiota is selected and maintained by the parasite regardless of the surrounding host microbiota. The parasite microbiota is important for its fitness, shown in vitro using an antibiotic motility assay and in vivo using germ free (GF) mice. Furthermore, infection with T. muris causes a significant reduction in caecal butyrate concentrations and consequently a decrease in the expression of butyrate transporters in caecal tissue. Interestingly, the T. muris microbiota is able to produce the short-chain fatty acid (SCFA) butyrate, which the parasite is unable to make itself yet secretes into its local environment. Together these strategies promote the long term survival of T. muris within the intestinal niche, adding a new level of complexity to the interaction between the pathogen, the host and their respective microbiotas that underpins successful chronic nematode infection.
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Raine, John Dale. "Proteomic analysis of the malarial parasite." Thesis, Imperial College London, 2005. http://hdl.handle.net/10044/1/11358.
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Tompkins, Daniel Michael. "Evolutionary ecology of bird-parasite associations." Thesis, University of Oxford, 1996. http://ora.ox.ac.uk/objects/uuid:a5f5ea19-b799-490b-b738-99ff52df25c1.
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This thesis investigates the ecological determinants of chewing louse (Insecta: Phthiraptera) host-specificity on four species of Malaysian swiftlets (Aves: Apodidae). Influences of host coloniality on louse ecology were also demonstrated, illustrating the dependence which these permanent ectoparasites have on their hosts. Louse collections were made to look for incidences of host-specific lice occurring on the "wrong" host ("straggling"). Straggling was observed, implying that lice disperse among host species. Thus, opportunity for louse dispersal (or lack thereof) does not govern the host-specificity of chewing lice on swiftlets. Experimental transfers of lice between hosts were conducted. Louse survival was reduced on foreign host species. This implies adaptation to specific host characters, suggesting that specialisation governs chewing louse host-specificity on swiftlets. There was no evidence for reciprocal adaptation of swiftlets to their normal louse species. Lice had no impact on the fitness of either swiftlets or the related common swift. Furthermore, neither swiftlet nor swift lice were transmitting pathogenic endoparasites. This implies that chewing lice and Malaysian swiftlets have not "coevolved". Survival of transferred lice was determined by the relatedness of donor and recipient hosts. Closer related swiftlet species are more similar in body size and feather dimensions. When the feather dimensions of the microhabitat distributions of the same louse species on different hosts were compared the results suggested that lice keep the dimensions of barb and barbule diameter, at which they occur, "constant" through microhabitat shifts. This suggests that feather dimensions are the host characters which determine the survival (and host-specificity) of chewing lice on birds. The ability of chewing lice to survive on hosts with similar feather morphology implies that "host-switching", between distantly related hosts with similar morphological characters (due to parallel or convergent host evolution), may have been an important factor in the evolution of bird-louse associations.
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Edwards, J. C. "Parasite-induced changes in host behaviour." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380108.
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Huggins, Mary L. "A parasite model for lung eosinophilia." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240928.
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