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dc.contributor.authorAlberdi Vélez, María Pilaren
dc.date.accessioned2018-05-14T10:20:49Z
dc.date.available2018-05-14T10:20:49Z
dc.date.issued2000en
dc.identifier.urihttp://hdl.handle.net/1842/30103
dc.description.abstracten
dc.description.abstractEhrlichia phagocytophila (Genus Ehrlichia, Order Rickettsiales) is the pathogen responsible for Tick-borne fever, a disease of high morbidity in susceptible ruminants. These bacteria appear to be almost identical at serological and molecular level to granulocytic Ehrlichia species recently diagnosed in humans, dogs and horses of Europe and the United States.en
dc.description.abstractA molecular description of different isolates of the pathogen is given. Samples were derived from wild and domestic vertebrate hosts from the UK, where Tick-borne fever is endemic. Molecular characterisation of a fragment from the groE operon gene showed higher nucleotide variation than at 16S rDNA level. Human and equine isolates from Europe differed from North American samples, which at 16S appeared to be identical. Further differences were also found between ruminant and non-ruminant granulocytic samples from Europe. Genomic analysis of less conserved genes appears necessary to provide more useful phylogenetic information that will help to clarify the relationship between closely related bacterial species.en
dc.description.abstractPopulations of the vector tick, Ixodes ricinus, were sampled and analysed to determine the prevalence of infection and clarify their role in the epidemiology of the disease. The studies indicated a low infection prevalence that seems, however, enough to maintain the pathogen in nature. The prevalence varied according to widespread sites across Britain but it was always lower than expected from information in the literature. Attempts to determine the efficiency of latent infection in sheep to transmit Ehrlichia to ticks were unsuccessful.en
dc.description.abstractA seroepidemiological survey was undertaken using IFAT and involving samples from suspected vertebrate reservoirs of infection such as dogs, cats, horses, and deer in order to determine if those species were exposed to the pathogen and the range of hosts for the bacteria in widespread sites across Britain. The results suggested high rates of exposure in dogs from rural areas and wild roe deer. Cats showed also a high seroprevalence indicating the three vertebrate hosts were exposed to E. phagocytophila and mounted an immune response towards the pathogen. It remains to be elucidated if dogs, cats and horses are accidental or competent reservoirs of infection. The presence of E. phagocytophila in roe deer blood and spleen samples was confirmed by PCR. Tick counts from deer legs ratified that all three stages of tick (larvae, nymphs and adults) were able to feed simultaneously upon roe deer thus supporting their role as competent reservoirs for both ticks and E. phagocytophila together with the serological and molecular evidence.en
dc.description.abstractCytoecetes ondiri, an African relative of Ehrlichia phagocytophila, was shown to cross-react in immunoblots with E. equi and in IFAT with E. phagocytophila antigens thus confirming a close antigenic relationship.en
dc.description.abstractELISA were developed using crude E. equi and E. phagocytophila as antigens and samples from several vertebrate species. The assays were validated with previous results obtained by IFAT. Data suggested that E. equi is a useful surrogate antigen for serologic studies until E. phagocytophila is routinely grown in culture. The antigenic structure of Ehrlichia was further characterised using mitochondria as surrogate antigens under the evidence of the phylogenetic relationship between the organelles and the bacteria. Ehrlichia are classified in the a-subgroup of Proteobacteria, which are believed to be the closest relatives to mitochondria. Sera from experimentally inoculated animals recognised mitochondrial antigens prior and after exposure but the responses were significantly higher after infection and challenge. Further work should be directed towards the successful cultivation of the pathogen as for HGE and E. equi in order to develop more reliable serological tests for E. phagocytophila for future epidemiological surveys. Identification of the major antigenic components of the organism will also help towards vaccine development.en
dc.publisherThe University of Edinburghen
dc.relation.isreferencedbyAlready catalogueden
dc.subjectAnnexe Thesis Digitisation Project 2018 Block 18en
dc.titleEpidemiology and molecular characterisation of Ehrlichia phagocytophila in relation to emerging ehrlichiaeen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


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