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Evaluation of bithional as a bath treatment for amoebic gill disease caused by Neoparamoeba spp

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Florent, RL and Becker, J and Powell, MD (2007) Evaluation of bithional as a bath treatment for amoebic gill disease caused by Neoparamoeba spp. Veterinary Parasitology, 144. pp. 197-207. ISSN 0304-4017

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Abstract

This study examined the toxicity of bithionol to Atlantic salmon Salmo salar and rainbow trout Oncorhynchus mykiss in fresh- and seawater and the efficacy of bithionol as a 1h seawater bath treatment for amoebic gill disease (AGD). To examine toxicity, fish were bathed for 1, 3 and 6h in bithionol, an anti-protozoal at 0, 1, 5, 10, 25 and 35mgL(-1) with toxicity determined by time to morbidity. Efficacy was examined by bathing AGD-affected Atlantic salmon and rainbow trout for 1h at bithionol concentrations of 1-25mgL(-1). Efficacy was determined by examining gill amoeba counts and identifying percent lesioned gill filaments at 1 and 24h after bath exposure to bithionol. For both species, bithionol was determined to be toxic at 25 and 35mgL(-1) exhibiting median lethal times (LT50s) ranging from 21 to 84min. Morbidity occurred in the 5 and 10mgL(-1) treatments, however, due to sampling regime there were not enough fish available to calculate LT50s. Only bithionol at 1mgL(-1) was considered non-toxic with no signs of morbidity. Bithionol was more toxic in seawater than freshwater and had no acute effects on gill Na+/K+ ATPase and succinic dehydrogenase, or plasma osmolality and chloride concentration. Bithionol at 1mgL(-1) reduced percent lesioned gill filaments in Atlantic salmon and rainbow trout by 33 and 27 per cent, respectively, compared to the seawater control. Similarly, numbers of amoeba were reduced by 33 and 43 per cent for Atlantic salmon and rainbow trout, respectively, when compared to the seawater control. Furthermore, bithionol reduced percent lesioned gill filaments as much as did the current industry standard of freshwater. This study demonstrated that a 1h seawater bath containing 1mgL(-1) bithionol could be an improvement to the current method of treatment for AGD-affected Atlantic salmon and rainbow trout.

Item Type: Article
Keywords: Salmo salar; Toxicity; Oncorhyncus mykiss; Ameobic gill disease; Efficacy; Bithionol; Neoparameobic spp; Protozoan parasaite
Journal or Publication Title: Veterinary Parasitology
Publisher: Elsevier BV
Page Range: pp. 197-207
ISSN: 0304-4017
Additional Information:

The definitive version is available at http://www.sciencedirect.com

Date Deposited: 07 Apr 2008 14:11
Last Modified: 18 Nov 2014 03:33
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