The efficacy of emamectin benzoate as an oral treatment of sea lice, Lepeophtheirus salmonis (Kroyer), infestations in Atlantic salmon, Salmo salar L

摘要

The efficacy of emamectin benzoate as an oral treatment of sea lice infestations in Atlantic salmon was evaluated in a dose titration study and 2 dose confirmation studies. Replicated groups of salmon with induced infestations of sea lice were treated daily with emamectin benzoate on pelleted feed at doses of 0, 25, 50 and 100μg/kg biomass for 7 consecutive days. Sea lice were counted at 7, 14 and 21 days from the start of treatment, and compared with control fish given the same diet without emamectin benzoate. Total numbers of sea lice were significantly reduced at all doses in all 3 studies when compared with control fish. There was no significant difference between doses of 50 and 100μg/kg, but the 50μg/kg dose resulted in significantly fewer lice than the 25μg/kg dose. Emamectin benzoate was highly effective in reducing numbers of pre-adult and adult lice and prevented the maturation of chalimus to motile stages. Treatment reduced the incidence of epidermal damage by sea lice and, in onestudy, survival of treated fish was 48% higher than in control groups. No fish mortalities or adverse effects were attributed to treatment with emamectin benzoate at any of the doses tested.