Amoebic gill disease in farmed halibut (Hippoglossus hippoglossus) in the United Kingdom

01 Mar 2019

Rodger, H. D.

Vet Record Case Reports Image

Amoebic gill disease (AGD) is one of the most significant infectious diseases affecting marine farmed Atlantic salmon and is caused by the marine amoeba Neoparamoeba perurans. Atlantic halibut are also farmed in Norway, Canada, Chile and Scotland; however, the total production is approximately 0.1 per cent that of salmon. Halibut reared in a net pen sea site in Scotland presented with low-level mortalities and pale, raised patches on the gills. Fresh microscopy of the gills demonstrated amoeboid organisms and histology of the gills confirmed typical AGD pathology. Gill samples tested by PCR confirmed the presence of N perurans. Freshwater baths of three hours duration are the preferred treatment for AGD in salmon; however, hydrogen peroxide has also been used and as halibut do not tolerate freshwater low-level hydrogen peroxide baths (1000 mg/l) were administered as a 15-minute bath. Net changes were also undertaken, and mortalities subsequently reduced.