In vitro anthelminthic activity of Lippia alba essential oil combined with silk fibroin against monogeneans of Colossoma macropomum (Serrasalmidae)

Essential oils have bioactive compounds that can be used against monogeneans and have low solubility in aqueous medium. This study investigated the in vitro anthelmintic efficacy of Lippia alba essential oil (320, 450, 550 and 640 mg/L) combined with a silk fibroin and isopropanol solution used as solvent in the control of monogeneans collected of gills from Colossoma macropomum (Cuvier, 1018). In vitro efficacy of 100% against Anacanthorus spathulatus (Kritsky, Thatcher & Kayton, 1979), Notozothecium janauachensis (Belmont‐Jégu, Domingues & Martins, 2004) and Mymarothecium boegeri (Cohen & Kohn,2005) was observed after 15 min of exposure to 640 mg/L of L. alba EO combined with silk fibroin solution, while 100% efficacy with exposure to 450 and 550 mg/L occurred after 2 and 1 h respectively. Structural changes to the tegument of the parasites exposed to L. alba EO combined with silk fibroin solution were observed with scanning electron microscopy. Therefore, the silk fibroin solution has potential as a solvent of essential oils and increased the anthelmintic effect of L. alba essential oil; thus, it should be tested in vivo for controlling and treating infections by monogeneans.