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Efficacy of bithionol as an oral treatment for amoebic gill disease in Atlantic salmon Salmo salar (L)

Florent, RL, Becker, J and Powell, MD 2007 , 'Efficacy of bithionol as an oral treatment for amoebic gill disease in Atlantic salmon Salmo salar (L)' , Aquaculture, vol. 270, no. 1- 4 , pp. 15-22 , doi:

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This study examined the efficacy of bithionol as an oral treatment for Atlantic salmon Salmo salar affected by amoebic gill
disease (AGD). The current commercial management strategy of AGD is a costly 3 h freshwater bath. It is labour intensive and the
number of baths needed appears to be increasing; hence, there is an effort to identify alternative treatments. Efficacy was examined
by feeding AGD-affected Atlantic salmon twice daily to satiation with bithionol, an antiprotozoal, at 25 mg kg−1 feed. Three
seawater (35‰, 17 °C) re-circulation systems were used each consisting of three tanks containing 32 Atlantic salmon smolts with
an average (±SEM) mass of 90.4 g (±5.2). Three feeds were examined in the trial including bithionol, plain commercial control
and oil coated commercial control. Feeding commenced 2 weeks prior to exposure to Neoparamoeba spp. at 300 cells L−1 and
continued for 28 days post-exposure. Efficacy was determined by examining gross gill score and identifying percent lesioned gill
filaments twice weekly for 4 weeks post-exposure. Bithionol when fed as a two-week prophylactic treatment at 25 mg kg−1 feed
delayed the onset of AGD pathology and reduced the percent lesioned gill filaments by 53% and halved the gill score from 2 to 1
when compared with both the plain and oil controls during an experimental challenge. There were no palatability problems
observed with mean feed intake of bithionol over the trial duration with fish consuming higher levels of the bithionol diet compared
to both the oil and plain controls. This study demonstrated that bithionol at 25 mg kg−1 feed, when fed as a two-week prophylactic
treatment for Neoparamoeba spp. exposure, delayed and reduced the intensity of AGD pathology and warrants further
investigation as an alternative to the current freshwater bath treatment for AGD-affected Atlantic salmon.

Item Type: Article
Authors/Creators:Florent, RL and Becker, J and Powell, MD
Keywords: Salmo salar; Amoebic gill disease (AGD); Bithionol; Neoparamoeba spp; Oral treatment; Protozoan parasite; Aquaculture
Journal or Publication Title: Aquaculture
Publisher: Elsevier BV
ISSN: 0044-8486
DOI / ID Number:
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