Clinical assessment of chloramine-T and freshwater as treatments for the control of gill amoebae in Atlantic salmon, Salmo salar L

• Published in: Aquaculture Research
• Main Authors: Harris, J, Powell, MD, Attard, M, DeHayr, L
• Format: Article in Journal/Newspaper
• Language: English
• Published: Blackwell Publishing 2005
• Subjects: Agricultural and Veterinary Sciences; Fisheries Sciences; Aquaculture; Atlantic salmon; Salmo salar
• Online Access: https://doi.org/10.1111/j.1365-2109.2005.01286.x; http://ecite.utas.edu.au/33303

Infections of gill amoebae that manifest as amoebic gill disease (AGD) occur in Atlantic salmon in Tasmania. The treatment of choice is freshwater bathing; however, the effectiveness of this treatment has declined over time. In this experiment, cage trials of chloramine-T (Cl-T) to treat AGD in Atlantic salmon were conducted over 3 months, and involved an initial bath in either freshwater or seawater with Cl-T, followed by a second bath 6 weeks later. Amoeba densities were reduced to 50-80% of original values for both treatments. Neoparamoeba sp. density was not affected by bathing, and was not significantly different over the course of the experiment. Lesion prevalence was higher for Cl-T-treated fish than for freshwater-treated fish, with overall prevalence levels of 14.30 1.00% and 8.03 0.57% respectively. This was also seen for gross gill scores. In the fortnight after each of the two baths, Cl-T-treated fish had significantly higher lesion levels, although this difference was then resolved by 4 weeks post bathing. The use of Cl-T in seawater is at least as effective as freshwater at reducing amoebae density, and may be a more practical alternative when freshwater is in short supply. 2005 Blackwell Publishing Ltd.