Evaluation of Low Temperature and Salinity as a Treatment of Atlantic Salmon against Amoebic Gill Disease.

Jemma Hudson,Tim Dempster,Mark Adams,Barbara F. Nowak,Khattapan Jantawongsri

doi:10.3390/microorganisms10020202

Jemma Hudson, Tim Dempster + Show 3 more

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https://doi.org/10.3390/microorganisms10020202

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Journal: Microorganisms	Publication Date: Jan 18, 2022
Citations: 3	License type: CC BY 4.0

Affiliation: University of Tasmania, University of Melbourne

Abstract

Amoebic gill disease (AGD) is a significant health issue for Atlantic salmon farmed in a marine environment. While the disease is currently managed using freshwater or hydrogen peroxide baths, there is a need to develop other treatments. The aims of this study were to examine the effect of salinity (0 ppt and 35 ppt) and temperature (3 °C and 15 °C) on attachment and survival of Neoparamoeba perurans in vitro over short exposure times (15 min and 2 h) and to assess the efficacy of reduced temperature (3 °C) as treatment for Atlantic salmon affected by AGD. In vitro freshwater 3 °C was at least as effective as freshwater 15 °C and the attachment was significantly lower after 2 h in freshwater 3 °C than freshwater 15 °C. In vivo there was no difference between the fish treated with freshwater 15 °C for 2 h or freshwater 3 °C. This study showed that despite exposure to low temperature reducing attachment of N. perurans to their substrate in vitro, 15 min cold-water bath treatment was not more effective at reducing AGD in Atlantic salmon than current commercial 2 h freshwater bath.

Highlights

Amoebic gill disease (AGD) was first reported in the late 1980s, in Atlantic salmon smolt farmed at Bruny Island in Tasmania, Australia, and in coho salmon (Oncorhynchus kisutch) farmed in Washington, USA [1,2]
The aims of this study were to examine the effect of salinity and temperature on attachment and survival of N. perurans In vitro over short exposure times and to assess the efficacy of reduced temperature as treatment for Atlantic salmon affected by AGD
There was no significant difference between the two freshwater treatments at 15 min; there was a significant difference between these treatments after 2 h with significantly higher percentage of attached amoebae at freshwater ppt (FW) 15 ◦ C (Figure 1)

Summary

Introduction

Amoebic gill disease (AGD) was first reported in the late 1980s, in Atlantic salmon smolt farmed at Bruny Island in Tasmania, Australia, and in coho salmon (Oncorhynchus kisutch) farmed in Washington, USA [1,2]. AGD is caused by Neoparamoeba perurans, which can parasitise gills of a number of host species [3]. The impact of the disease has been substantial to the salmon industry, causing significant increases in production costs due to treatment, mortalities, and reduced growth of fish. Treatment is estimated to cost the Atlantic salmon industry in Tasmania around $40 million annually, increasing the cost of production by. Comparisons of impacts of parasitic diseases on mariculture industry globally have suggested that AGD has one of the highest economic impacts [6]. The methods to treat fish affected by AGD on a commercial scale are limited to the use of freshwater or hydrogen peroxide baths

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