DAO 95:65-71 (2011)  -  DOI: https://doi.org/10.3354/dao02341

Francisella noatunensis subsp. noatunensis is the aetiological agent of visceral granulomatosis in wild Atlantic cod Gadus morhua

Mulualem Adam Zerihun1,*, Stephen W. Feist2, David Bucke3, A. B. Olsen4, Nora M. Tandstad1, Duncan J. Colquhoun1

1The Norwegian Veterinary Institute, Ullevaalsveien 68, 0106 Oslo, Norway
2Centre for Environment, Fisheries and Aquaculture Science, Barrack Road, The Nothe, Weymouth, Dorset DT4 8UB, UK
33b Roundhayes Close, Weymouth, Dorset DT4 0RN, UK
4The National Veterinary Institute, PB 1263, 5003 Bergen, Norway

ABSTRACT: During the 1980s and 1990s wild-caught cod displaying visceral granulomatosis were sporadically identified from the southern North Sea. Presumptive diagnoses at the time included mycobacterial infection, although mycobacteria were never cultivated or observed histologically from these fish. Farmed cod in Norway displaying gross pathology similar to that identified previously in cod from the southern North Sea were recently discovered to be infected with the bacterium Francisella noatunensis subsp. noatunensis. Archived formalin-fixed paraffin-embedded tissues from the original North Sea cases were investigated for the presence of Mycobacterium spp. and Francisella spp. using real-time polymerase chain reaction, DNA sequencing and immunohistochemistry. Whilst no evidence of mycobacterial infection was found, F. noatunensis subsp. noatunensis was identified in association with pathological changes consistent with Francisella infections described from farmed cod in recent years. This study shows that francisellosis occurred in wild-caught cod in the southern North Sea in the 1980s and 1990s and demonstrates that this disease predates intensive aquaculture of cod.


KEY WORDS: Francisellosis · Francisella noatunensis · Mycobacterium · Granulomatosis · Myco­bacteriosis · Atlantic cod · Immunohistochemistry · Real-time PCR · Formalin-fixed paraffin-embedded tissue


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Cite this article as: Zerihun MA, Feist SW, Bucke D, Olsen AB, Colquhoun NMTDJ (2011) Francisella noatunensis subsp. noatunensis is the aetiological agent of visceral granulomatosis in wild Atlantic cod Gadus morhua. Dis Aquat Org 95:65-71. https://doi.org/10.3354/dao02341

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