The susceptibility of salmonid fish to an atypical strain of Aeromonas salmonicida that infects goldfish, Carassius auratus (L.), in Australia

An enzootic, Australian, atypical strain oi Aeromonas salmonicida isolated from diseased goldfish, Carassius auratus (L.), was inoculated into Atlantic salmon, Salmo salar L.. brown trout, 5. trutta L.. rainbow trout, S. gairdneri Richardson, and brook trout. Salvelinus fontinalis (Mitchill), fingerlings by intraperitoneal injection (i.p.) and by bath challenge, the latter with and without prior abrasion of skin. The 10-day LDs(j (i-p.) was estimated to be 7-4 x 10^-^ colony forming units (cfu) for Atlantic salmon, 3-Ox 10 -cfu for brown trout, 3-7x10-cfu for brook trout and 6-4x10^ cfu for rainbow trout. Brown, rainbow and brook trout succumbed to bath challenges with between 10-\u27\u27-10^cfu/mI, developing ulcers of the skin and septicaemia. The organism was trasmitted from inoculated fish to five of 195 within-tank control fish via water and established a carrier state in one of 14 Atlantic salmon. It was concluded that the organism poses a significant threat to the salmonid farming industry and wild saimonid fisheries in Australia