Rickettsia-like organism in farmed salmon
Grant, A.N.; Brown, A.G.; Cox, D.I.; Birkbeck, T.H.; Griffen, A.A.
Veterinary Record 138(17): 423
1996
ISSN/ISBN: 0042-4900 PMID: 8733186 Document Number: 462343
In November 1995, abnormal swimming, skin damage and increased mortality was seen in Atlantic salmon (Salmo salar) in several pens on 2 fallow marine farms on the same Scottish loch; several thousand fish died. The farms had been stocked with healthy smolts from several sources 7 months previously. Except for splenomegaly, gross pathology was unremarkable. Histopathological changes included areas of encephalitis and vasculitis in the brain with associated basophilic intracellular coccoid bodies. Brain tissue from affected fish were cultured on Chinook salmon embryo (CHSE) cells and produced cytopathic effects, Rickettsia-like organisms were seen in culture supernatant using electron microscopy; the organism failed to react in a test for Piscirickettsia salmonis. Culture supernatant injected into disease-free fish produced 100% mortality within 18 days and the organism was reisolated from dead fish. Further investigations to fully identify the organism are underway.