Heart and skeletal muscle inflammation (HSMI) in Atlantic salmon: diagnosis, pathogenesis and epidemiology

Heart and skeletal muscle inflammation (HSMI) is a transmissible disease of viral aetiology affecting farmed Atlantic salmon. The disease appears to be spreading rapidly into new areas, and it is important to limit further spread. HSMI is characterized by severe inflammation in heart and red skeletal muscle. The pathogenesis is uncertain, but studies suggest that the disease process may start several months before clinical symptoms are observed. Characterization of the viral agent is ongoing; however ther e are at present no diagnostic methods available to detect the virus in diseased fish. The current lack of accurate diagnostic tools causes particular problems in distinguishing between HSMI, pancreas disease and cardiomyopathy syndrome in atypical cases and when concurrent disease outbreaks are suspected. In the present project we will attempt to develop direct and indirect antigen detection by immunohistochemistry, PCR and serology. These tools will further be used to study the pathogenesis of HSMI. We will particularly study the distribution of virus during disease progression, as well as characterize the inflammatory reaction. As HSMI is spreading quickly into new areas, it is also important to predict the potential of dispersion. A dispersal model fo r infectious salmon anaemia has recently been developed. This will form the basis of a similar model for HSMI. More accurate diagnostic methods, increased knowledge of pathogenesis and the ability to predict the spread of HSMI, may facilitate efficient su rveillance and prevention of future HSMI outbreaks.