Occurrence of the tuna nematode Hysterothylacium cornutum (Stossich, 1904) in farmed Atlantic cod Gadus morhua L. in North Norway

摘要

Adult and fourth-stage larval nematodes found in the stomachs of farmed cod in North Norway in October 2006 were identified as Hysterothylacium cornutum (Stossich, 1904), a nematode considered to be specific at the adult stage to tunas of the genus Thunnus. As far as we are aware, this is the first report of an adult form of this nematode from any host other than members of the genus Thunnus, and is also the first report from a polar region. The two infected cod, one with one large adult worm and another with six larvae, were in a sample of 17 that had been captured from the wild about 1 year before sampling and held in floating sea cages in 0ksfjord, Finnmark County, North Norway, where the examinations took place. No further infections were found in any other samples of wild and farmed cod, totalling 261 fish, examined by us during the period 2006 and 2007 from five locations distributed along the coast of Norway from 0ksfjord in the north to Alesund in the south. Possible sources of this unusual infection are discussed, but no firm conclusion could be reached.