DAO 91:257-262 (2010)  -  DOI: https://doi.org/10.3354/dao02269

NOTE
In vitro toxicity of bithionol and bithionol sulphoxide to Neoparamoeba spp., the causative agent of amoebic gill disease (AGD)

Renee L. Florent1, Joy A. Becker1,2, Mark D. Powell1,3,*

1Aquafin CRC, National Centre for Marine Conservation and Resource Sustainability, University of Tasmania, Locked Bag 1370 Launceston, Tasmania 7250, Australia
2Faculty of Veterinary Science, University of Sydney, 425 Werombi Road, Camden, NSW 2570, Australia
3Faculty of Biosciences and Aquaculture, Bodø University College, Postboks 1490, Bodø, N-8049, Norway
*Corresponding author. Email:

ABSTRACT: The objective of the present study was to evaluate the in vitro toxicity of bithionol and bithionol sulphoxide to Neoparamoeba spp., the causative agent of amoebic gill disease (AGD). The current treatment for AGD-affected Atlantic salmon involves bathing sea-caged fish in freshwater for a minimum of 3 h, a labour-intensive and costly exercise. Previous attempts to identify alternative treatments have suggested bithionol as an alternate therapeutic, but extensive in vitro efficacy testing has not yet been done. In vitro toxicity to Neoparamoeba spp. was examined using amoebae isolated from the gill of AGD-affected Atlantic salmon and exposing the parasites to freshwater, alumina (10 mg l–1), seawater, bithionol or bithionol sulphoxide at nominal concentrations of 0.1, 0.5, 1, 5 and 10 mg l–1 in seawater. The numbers of viable amoebae were counted using the trypan blue exclusion method at 0, 24, 48 and 72 h. Both bithionol and bithionol sulphoxide demonstrated in vitro toxicity to Neoparamoeba spp. at all concentrations examined (0.1 to 10 mg l–1 over 72 h), with a comparable toxicity to freshwater observed for both chemicals at concentrations >5 mg l–1 following a 72 h treatment. Freshwater remained the most effective treatment, with only 6% viable amoebae seen after 24 h and no viable amoebae observed after 48 h.


KEY WORDS: Amoebic gill disease · AGD · Bithionol · In vitro · Toxicity · Neoparamoeba spp. · Atlantic salmon · Chemotherapy · Protozoan parasite


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Cite this article as: Florent RL, Becker JA, Powell MD (2010) In vitro toxicity of bithionol and bithionol sulphoxide to Neoparamoeba spp., the causative agent of amoebic gill disease (AGD). Dis Aquat Org 91:257-262. https://doi.org/10.3354/dao02269

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