“…The compound included on pacu diet is a synthetic anthelmintic extensively applied in veterinary and human treatments, and has shown a potent immune modulatory action on innate and acquired immune systems of several species, such as Sparus aurata, Salmo salar, Oncorhynchus mykiss and Cyprinus carpio (Siwicki, 1989;Jeney and Anderson, 1993;Mulero et al, 1998;Findlay and Munday, 2000;Cuesta et al, 2002Cuesta et al, , 2004. Therefore, levamisole has prompt resistance against various etiological agents, such as Vibrio anguillarum, A. hydrophila, Paramoeba sp., Edwardsiella tarda, Photobacterium damselae and nematodes as Anguillicola crassus (Kajita et al, 1990;Geets et al, 1992;Baba et al, 1993;Findlay et al, 2000; Leano et al, 2003;Munday and Zilberg, 2003).…”