Efficacy of Emamectin Benzoate Figure 4. Profile plots for treatment episodes showing post-treatment mobile abundances associated with significant (p,0.05) interaction factors. Post-treatment mobile L. salmonis abundances with associated 95% confidence intervals. Based on a GLM analysis of data from 108 treatment episodes at 47 Atlantic salmon farms in Scotland in the period 2002 to 2006. doi:10.1371/journal.pone.0001549.g004 (around 50% of the initially available episodes in each case) after appropriate data screening criteria had been applied. While both of these North American studies presented a snapshot of treatment efficacy within their respective geographical regions, neither attempted to show whether the efficacy of emamectin benzoate had changed over a period of time. Prospective efficacy studies tend to be based on a relatively small numbers of treatment episodes. However, they are normally strictly controlled and often have complete and balanced data sets collected by a dedicated group of individuals working to a standard clinical efficacy protocol [20,33]. While laboratory based studies were essential in establishing the efficacy of emamectin benzoate, they may not accurately reflect its performance under commercial conditions. A number of case studies have also been conducted to assess emamectin benzoate efficacy in the field; however several had to medicate the untreated ‘‘controls’’ with alternative ectoparasiticides before the planned completion date in order to avoid unacceptably high levels of infestation [21,22,34]. PLoS ONE | www.plosone.org 8 February 2008 | Volume 3 | Issue 2 | e1549