DAO 94:41-57 (2011)  -  DOI: https://doi.org/10.3354/dao02313

Diseases of farmed Atlantic salmon Salmo salar associated with infections by the microsporidian Paranucleospora theridion

S. Nylund1,*, L. Andersen1, I. Sævareid1, H. Plarre1, K. Watanabe1, C. E. Arnesen2, E. Karlsbakk3, A. Nylund

1Department of Biology, University of Bergen, 5020 Bergen, Norway
2Firda Seafood AS, 5966 Eivindvik, Norway
3Institiute of Marine Research, 5817 Bergen, Norway

ABSTRACT: The microsporidian Paranucleospora theridion was discovered in Atlantic salmon Salmo salar suffering from proliferative gill disease in a marine farm in western Norway in 2008. The parasite develops in cells of the reticuloendothelial system, cells important for normal immune function. The aim of this study was to see if P. theridion could play a part in some of the diseases with unclear causes in salmon production in Norway, i.e. proliferative gill disease (PGI), pancreas disease (PD), heart and skeletal muscle inflammation (HSMI) and cardiomyopathy syndrome (CMS). P. theridion was present in all areas with salmon farming in Norway, but high prevalence and densities of the parasite in salmon and salmon lice were only seen in southern Norway. This region is also the main area for PGI and PD in Norway. Quantification of pathogens associated with PGI, PD, HSMI and CMS diagnoses showed that P. theridion levels are high in southern Norway, and may therefore play a role in susceptibility and disease development. However, among the different diagnoses, fish with PGI are particularly heavily infected with P. theridion. Therefore, P. theridion appears as a possible primary agent in cases with high mortality in connection with PGI in western Norway.


KEY WORDS: Paranucleospora theridion · Atlantic salmon · Microsporidia · Proliferative gill disease · PGI · Pancreas disease · PD


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Cite this article as: Nylund S, Andersen L, Sævareid I, Plarre H and others (2011) Diseases of farmed Atlantic salmon Salmo salar associated with infections by the microsporidian Paranucleospora theridion. Dis Aquat Org 94:41-57. https://doi.org/10.3354/dao02313

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