DAO 67:47-54 (2005)  -  doi:10.3354/dao067047

Atlantic salmon paramyxovirus (ASPV) infection contributes to proliferative gill inflammation (PGI) in seawater-reared Salmo salar

Agnar Kvellestad1,2,*, Knut Falk2, Solveig M. R. Nygaard3, Kjell Flesjå4, Jan Arne Holm5

1Department of Basal Medicine and Aquatic Sciences, Norwegian School of Veterinary Science, PO Box 8146 Dep., 0033 Oslo, Norway
2National Veterinary Institute, PO Box 8156 Dep., 0033 Oslo, Norway
3Fish Health and Environment Company, Ramsvollsveien 1, 5518 Haugesund, Norway
4National Veterinary Institute, PO Box 295, 4303 Sandnes, Norway
5Fjord-Lab AS, PO Box 7, 6701 Måløy, Norway

ABSTRACT: Proliferative gill inflammation (PGI) causes significant losses in farmed Atlantic salmon Salmo salar L. in Norway, especially during the first months following seawater transfer. The aetiology is apparently multifactorial, including infection with chlamydia-like bacteria and Atlantic salmon paramyxovirus (ASPV). In the present study, gills from diseased fish from 3 farms on the western coast of Norway were sampled. The pathological changes were briefly described and the aetiological significance of ASPV studied by immunofluorescent staining of cryosections and by immunohistochemistry on sections of formalin-fixed and paraffin-embedded tissue. The pathological changes were macroscopically characterized by palour of the gills, and histologically by inflammation, circulatory disturbances, cell death and epithelial cell proliferation. ASPV was demonstrated in fish from all farms studied, as immunostaining consistent with ASPV was obtained in lamellar epithelial and endothelial cells of pathologically altered tissues. It is concluded that ASPV is at least a contributing cause of PGI. As far as we know, this is the first demonstration of fish disease related to infection with a paramyxovirus.

KEY WORDS: Atlantic salmon · Salmo salar · Proliferative gill inflammation · PGI · Epitheliocystis · Atlantic salmon paramyxovirus · ASPV · Immunofluorescence · Immunohistochemistry

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