| Summary: | Salmon Pancreas Disease Virus (SPDV) is the only viral species of the genus Alphavirus, family Togaviridae, affecting fish. SPDV induces two conditions historically recognised independently as Pancreas disease (PD) and Sleeping disease (SD), affecting Atlantic salmon (Salmo salar L) and rainbow trout (Oncorhynchus mykiss), respectively. Infection by SPDV can lead to clinical disease with characteristic acinar pancreatic necrosis and a range of myopathies of the skeletal and heart muscle. Mortality is not a necessary outcome of the disease and usually is not significant. However, affected fish stop eating and therefore present a reduced growth rate and the disease can also leave visible lesions at the fillet level that lead to downgrading at slaughter. SPDV can affect in the fresh and sea water environments, but a higher and most relevant impact reported in the latter. Historically, PD has posed a significant challenge to the Atlantic salmon farming industry in the UK, as well as in other salmon producing countries. This thesis was developed and conducted at Marine Scotland Science (MSS), the Scottish National Reference Laboratory, with the aim to contribute to knowledge gaps identified by the industry and research communities. The focus was on development and improvement of in vivo and in vitro infection models to assist with host pathogen interaction studies. In vivo work was to establish an experimental challenge model to induce SPDV infection in a more natural way than by intra-peritoneal (IP) injection. The first step involved selection of an infective SPDV isolate through a comparative IP challenge study. An infective isolate was then used to establish a co-habitation challenge model in “post smolts”, the sea-water stage predominantly affected by PD. Additionally, during this experiment assessment of viral tissue tropism along time and potential intra-subtype differences in infectivity was undertaken. In vitro work accounted for the more innovative part of this thesis with the development, optimization and ...
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