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

Abstract

The efficacy of emamectin benzoate as an oral treatment of sea lice, Lepeophtheirus salmonis (KrÒyer), infestations in Atlantic salmon, Salmo salar L., was evaluated in a dose titration study and two dose confirmation studies. Replicated groups of salmon with induced infestations of sea lice were given emamectin benzoate on pelleted feed at doses of 0, 25, 50 and 100 μg kg−1 biomass day−1 for seven consecutive days. Sea lice were counted at 7, 14 and 21 days from the start of treatment, and comparisons made with control fish given the same diet without emamectin benzoate. Total numbers of sea lice were significantly reduced at all doses in all three studies when compared to control fish. There was no significant difference between doses of 50 and 100 μg kg−1, but the 50 μg kg−1 dose resulted in significantly fewer lice than the 25 μg kg−1 dose. Emamectin benzoate was highly effective in reducing numbers of preadult and adult lice and prevented the maturation of chalimus to motile stages. The optimum therapeutic dose was selected as 50 μg kg−1 day−1 for seven days. Treatment reduced the incidence of epidermal damage by sea lice and, in one study, 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.

Effects of salmon lice infection on the behaviour of sea trout in the marine phase

“…Reduced sensitivity to EB could potentially be an issue (Igboeli et al 2012), but the skin concentration of EB was much higher than the level typically obtained by oral administration (Skilbrei et al 2008). The treatment efficacy (sensu Stone et al 2000) of 42.7% observed in the present study was also within the ranges of 30−60% that could be expected after a week of oral treatment (Stone et al 1999(Stone et al , 2000. The salinity was not measured at the experiment cage location, but as discussed above (in 'Infestation, swimming depth and distance to the river outlet'), we can reasonably assume that there was a low-salinity layer extending at least 1−2 m downwards.…”

“…2b). Thus, the EB treatment effect was a 31.6% intensity reduction over the experiment duration of 8 d. The treatment efficacy (sensu Stone et al 1999Stone et al , 2000 was 42.7%. The decline in intensity was statistically significant in both groups, and treatment and initial intensity had significant negative effects on infestation growth (model r~ Treatment + Initial intensity, p Intercept < 0.001, p Treatment < 0.001, p Initial intensity = 0.025, adj.…”

“…For comparison with earlier studies, the prophylaxis efficacy (Stone et al 1999(Stone et al , 2000 was calculated based on the percentage of surviving lice on individual hosts in the treatment and control groups:…”

Efficacy of emamectin benzoate in the control of Argulus coregoni (Crustacea: Branchiura) on rainbow trout Oncorhynchus mykiss

“…The efficacy of emamectin benzoate (50 µg kg -1 for 7 d) has been demonstrated against the parasitic copepods Lepeophtheirus salmonis and Caligus elongatus on Atlantic salmon Salmo salar (Stone et al 1999, 2000a,b,c, Treasurer et al 2002, and Salmincola edwardsii on brook trout, Salvelinus fontinalis (Duston & Cusak 2002). Stone et al (2000a) ascertained that the duration of efficacy against L. salmonis on salmon was up to 10 wk.…”

Randomized clinical trial to investigate the effectiveness of teflubenzuron for treating sea lice on Atlantic salmon

“…first summer in sea cages). Emamectin, another oral formulation in the avermectin family, is currently being used through emergency drug release (EDR) but was not available at the time this trial was conducted (Stone et al 1999, Armstrong et al 2000.…”