Essential oil of Alpinia zerumbet (Zingiberaceae) has anthelmintic efficacy against monogenean of Colossoma macropomum (Characiformes: Serrasalmidae)

This study investigated for the first time the anthelmintic efficacy of essential oil (EO) of Alpinia zerumbet Burt & Smith against monogeneans of Colossoma macropomum (Cuvier, 1818), as well as the blood and histological effects in this fish. In in vitro assays, different concentrations of A. zerumbet EO (300, 600, 1200 and 2400 mg/L) and two control groups were evaluated: with water from the culture tank and water from the culture tank +70% alcohol. Monogeneans showed 100% immobilization in vitro with all tested EO concentrations, with a dose-dependent effect. Scanning electron microscopy showed that the monogeneans exposed to A. zerumbet showed deep wrinkling in the integument. The fish showed tolerance to the concentration of 300 mg/L of A. zerumbet EO, which was used in therapeutic baths for six consecutive days. Therapeutic baths with 300 mg/L of A. zerumbet EO had anthelmintic efficacy of 94% and low toxicity to fish, as there were few changes to the blood parameters (plasma glucose and total protein, number of leukocytes, neutrophils and monocytes) and mild changes histopathological findings that did not compromise the functioning of the gills of C. macropomum. Therefore, 300 mg L-1 of A. zerumbet EO can be used in therapeutic baths to control and treat infections by monogeneans in C. macropomum.