Bacterial Gill Disease (BGD)A disease that may affect any fish cultured intensively. BGD is caused by a number of different bacteria that infect the gills of fish. The disease is characterized by the presence of large numbers of filamentous bacteria on the gills accompanied by clubbing and fusing of the gill filaments. This reduces the ability of the gills to supply oxygen to the blood and results in mortality if left unchecked. The onset of BGD is usually linked to a decline in environmental conditions in combination with overcrowding.
The best treatment is prevention through maintenance of optimum rearing densities and keeping rearing units as clean as possible to prevent the growth of bacteria. A flow through treatment of Chloramine-T for 60 minutes at 8.0 parts per million is usually effective in eradicating the disease. The U.S. Food and Drug Administration (USFDA) have not yet approved Chloramine-T for general use. State hatcheries use this drug under a special permit (INAD) issued by the USFDA.