Efficacy of emamectin benzoate sea lice treatments
|Title||Efficacy of emamectin benzoate sea lice treatments|
|Author(s)||F. Lees, M. Baillie, G. Gettinby, C. Revie|
|Abstract||In order to investigate whether the efficacy of emamectin benzoate (SLICE) against sea lice (Lepeophtheirus salmonis) infestation in Atlantic salmon had changed in Scotland, UK, in the period since regular application of the drug began, sea lice abundance and treatment data were examined from 56 west coast salmon farms between 2002 and 2006. There were 108 treatments during the study period. It was shown that treatments administered in 2002 and 2003 appeared to be highly effective, with 100 and 95% reduction in mobile lice within 34 days of treatment, respectively. Efficacy remained above 60% throughout the 7-83-day period following treatment in both years. In 2004, SLICE reduced mobile lice abundance by 84% and by 70% in 2005. However, it took 49-55 days to reach this level of efficacy. In 2004 treatment efficacy remained above 50% for the rest of the 83-day period, but in 2005 it declined more rapidly and had fallen below 20% by day 83. Maximum efficacy was reached between days 56 and 62 in 2006, when mobile lice abundance was reduced by more than 65%. However, by day 69 lice levels had risen again to above pretreatment levels. Post-treatment mobile L. salmonis abundance was significantly higher in 2005 and 2006 when compared to earlier years. Mobile lice abundance in the 12-week period following an ineffective treatment was about 10 times higher compared to an effective one. A significant difference in post-treatment abundance was also observed among the 3 geographical regions on Scotland's west coast.|
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