Efficacy of Fumagillin DCH against experimentally induced Loma salmonae (Microsporea) infections in chinook salmon Oncorhynchus tshawytscha

Loma salmonae (Microsporea) is a serious gill pathogen of seawater pen-reared chinook salmon Oncorhynchus tshawytscha.Fumagillin DCH has been used to control other microsporean and myxosporean diseases of fishes, and the efficacy of this drug for controlling L. salmonae infections was investigated.Chinook salmon were experimentally infected with L. salmonae in seawater tanks.At 1 wk post initial exposure, 2 tanks of 12 fish each were fed Fumagillin DCH in the diet at 10 mg drug kg-' fish d-' for 30 d, and 2 other tanks of exposed fish were maintained as non-treated controls.None of the surviving 22 Fumagillin-treated fish exhibited L. salmonae infections when examined at 44 d post initial exposure, while 13 of 21 untreated fish were infected.This preliminary study suggests that Fumagillin DCH may be a useful therapeutant for controlling L. salmonae infections.