Amoebic gill disease in hatchery-reared ayu, Plecoglossus altivelis (Temminck & Schlegel), in Japan is caused by Neoparamoeba perurans

摘要

Amoebic gill disease (AGD) is a potentially fatal infection in fish farmed in marine environments and has been reported throughout the world in numerous species, including salmonids (Kent, Sawyer & Hedrick 1988; Munday, Foster, Roubal & Lester 1990) and turbot (Dyková, Figueras & Novoa 1995). Gill pathology, including epithelial hyperplasia resulting in lamellar fusion, is usually initiated by colonisation and proliferation of a marine amoeba harbouring an endosymbiont, on the gills of susceptible fish (Adams & Nowak 2003, 2004). Neoparamoeba perurans has been shown to be the AGD-causing agent in Atlantic salmon from Australia, the USA, Scotland and Ireland; rainbow trout from Tasmania; chinook salmon from New Zealand, and turbot from Spain (Young, Dyková, Snekvik, Nowak & Morrison 2008a). The first reported outbreak of AGD in farmed Atlantic salmon in Norway was attributed to N. perurans infection based on sequence analyses of 18S cDNA derived from AGD-affected gill tissue (Steinum, Kvellestad, R?nneberg, Nilsen, Asheim, Fjell, Nyg?rd, Olsen & Dale 2008).