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dc.contributor.authorBeard, Philippa Maryen
dc.date.accessioned2018-05-14T10:14:43Z
dc.date.available2018-05-14T10:14:43Z
dc.date.issued2001en
dc.identifier.urihttp://hdl.handle.net/1842/29893
dc.description.abstracten
dc.description.abstractParatuberculosis is a common and fatal disease of ruminants, caused by the bacterium Mycobacterium avium subsp. paratuberculosis (M.a. paratuberculosis). The disease causes significant economic and welfare concerns for affected farms and ruminant livestock industries worldwide, however, the pathogenesis and epidemiology of paratuberculosis are poorly understood, resulting in few successful strategies available for control or prevention programmes. This thesis describes investigations into three aspects of the epidemiology and pathogenesis of paratuberculosis - the extent to which non-ruminant wildlife are infected with M.a. paratuberculosis, the initial host response to M.a. paratuberculosis exposure, and, finally, the influence of host genotype on susceptibility to the disease.en
dc.description.abstractIn response to the recent discovery of natural M.a. paratuberculosis infection of non-ruminant wildlife in Scotland, the pathology of natural rabbit paratuberculosis was investigated and described. Infected rabbits exhibited mild or severe histopathological lesions in the gastrointestinal tract and associated lymphoid tissues. M.a. paratuberculosis was cultured from both the faeces and urine of naturally infected rabbits, revealing two possible routes of transmission of the organism.en
dc.description.abstractTo investigate the impact of natural rabbit paratuberculosis on the disease in ruminant livestock, young calves were orally inoculated with an isolate of M.a. paratuberculosis from a naturally infected rabbit. After an incubation period of six months, the organism was recovered from the intestinal tissues of seven out of eight inoculated calves, with three of these calves also exhibiting pathological changes consistent with chronic paratuberculosis. This indicates that M.a. paratuberculosis organisms excreted by infected rabbits have the potential to cause paratuberculosis in cattle. In a parallel experiment, two groups of rabbits were inoculated with either a bovine or leporine-derived isolate of M.a. paratuberculosis but no evidence of infection was noted in any animal after a six month incubation period, implying that further, as yet unidentified factors, are involved in the pathogenesis of paratuberculosis in rabbits.en
dc.description.abstractThe discovery of paratuberculosis in rabbits has resulted in a reassessment of the natural host range of M.a. paratuberculosis. A survey of wildlife in rural Scotland was undertaken to 10 determine the extent of natural non-ruminant paratuberculosis infection. It revealed evidence of infection in 10 species of wildlife - fox, stoat, weasel, crow, rook, jackdaw, rat, wood mouse, hare and badger. This is the first report of natural M.a. paratuberculosis infection in any of these species. The results from this survey were compared with two further investigations. A group of 27 foxes from urban areas of London, with no known exposure to paratuberculosis-affected ruminants or rabbits, were examined, but no evidence of M.a. paratuberculosis infection was detected. This implies that M.a. paratuberculosis infection of foxes is dependent on contact with infected ruminants or rabbits. However, screening of foxes and rabbits from four paratuberculosis-affected farms in Northern England did not reveal any evidence of natural paratuberculosis, suggesting that the mere presence of paratuberculosis in domestic animals may not be sufficient for infection of wildlife to occur. Further investigations are indicated to clarify the inter-relationships of paratuberculosis cycles in domestic ruminants, rabbits, and other species of wildlife.en
dc.description.abstractImmunological changes following oral inoculation with M.a. paratuberculosis were investigated in young lambs. After an incubation period of four weeks, analysis of the lymphocyte subsets present in the jejunal and ileal Peyer's patches and mesenteric lymph node revealed a predominately cell mediated immune response. Using immunohistochemical methods, an increase in the number of γδ T cells in the jejunal and ileal Peyer's patches was demonstrated, indicating a possible role for this class of T cells in the early immune response to M.a. paratuberculosis exposure. No change in the number of CD1* cells was apparent in the intestinal lymphoid tissue in response to M.a. paratuberculosis inoculation.en
dc.description.abstractPreliminary evidence of genetic susceptibility to paratuberculosis was identified in a naturally infected flock of sheep, with the offspring of one ram exhibiting a statistically higher incidence of the disease when compared with the offspring of the other sires (p=0.019), indicating that host genotype may have an effect on susceptibility to paratuberculosis. A specific base pair substitution in the natural resistance associated macrophage protein (NRAMP) gene is known to confer susceptibility to murine mycobacterial infection, however, analysis of the genome of 18 paratuberculosis-affected and 60 clinically normal ruminants revealed no evidence of this mutation.en
dc.publisherThe University of Edinburghen
dc.relation.isreferencedbyAlready catalogueden
dc.subjectAnnexe Thesis Digitisation Project 2018 Block 18en
dc.titleEpidemiology and pathogenesis of paratuberculosisen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


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