| As the culture of marine fish and shellfish species increases, diseases commonly afflicting their wild counterparts have been detected in cultured animals. Nodavirus disease (NNV) is one of these and is commonly referred to as viral nervous necrosis, viral encephalopathy and retinopathy, fish encephalitis or encephalomyelitis. As there are no vaccines against NNV, the aquaculture industry currently relies on sanitation practices and eradication of populations deemed infected.; In chapter 2, the use of in-situ hybridization for localizing nodavirus in tissues of larval Atlantic cod was developed and optimized. Using this technique the route of entry and distribution of the virus in Atlantic cod larvae was examined and determined to be the gill arches and digestive tract.; In chapter 3, the role of temperature as a trigger of nodavirus disease was investigated through generating carriers and holding them at a non-stressful (ambient, 5.8-8.6°C) and stressful (17°C) temperature. The effects of temperature and virus exposure on the expression of ISG15 were also examined. One of the earliest and most expressed immune genes is ISG15 (interferon stimulated gene 15), suggesting it has an important role in the IFN system. As ISG15 protein expression is one of the first lines of immune system defence and plays a vital role in the innate immune system and antiviral response this was done to access the role that the interferon system plays in the maintenance of the carrier state and whether elevated temperatures change the pattern of expression. ISG15 levels were seen to be elevated at one day post-injection, lowered at day 7 and again were slightly elevated again at day 14. The results presented here add to our knowledge of the pathogenicity of nodavirus and the cod immune response. |
