Atividade anti-helmíntica do óleo essencial de Alpinia zerumbet (ZINGIBERACEAE) em monogeneas, com avaliação hematológica e histopatológica em Colossoma macropomum (SERRASALMIDAE)

Abstract

This study investigated, for the first time, the anthelmintic efficacy of Alpinia zerumbet essential oil (EO) against monogeneans of Colossoma macropomum, as well as the blood and histopathological effects of this essential oil for this fish. In in vitro tests, different concentrations of the essential oil of A. zerumbet (300, 600, 1200 and 2400 mg L-1 ) and two control groups (one with water from the culture tank and other with water from the culture tank + 70% ethyl alcohol) were evaluated. The majority components of EO were terpinen-4-ol (27.7%), eucalyptol (19.2%) and γ-terpinene (14.9%). Tolerance tests showed that C. macropomum tolerates exposure to 300 mg L-1 of A. zerumbet EO, the concentration used in therapeutic baths. In therapeutic baths, the fish were exposed to 300 mg L-1 of A. zerumbet EO for 30 minutes, for six consecutive days. After the therapeutic baths, the gills of the fish were collected to quantify the parasite and to determine the prevalence and mean abundance of parasites and to carry out the histopathological analyzes. Blood samples were also taken to determine blood parameters such as erythrocytes, leukocytes and biochemical. The monogeneans Anacanthorus spathulatus, Mymarothecium boegeri and Notozothecium janauachensis had 100% immobilization in vitro at all EO concentrations tested, with a dose dependent effect. Scanning electron microscopy studies showed that the parasite exposed to A. zerumbet EO showed deep wrinkling in the integument. The fish showed tolerance to the concentration of 300 mg L-1 of A. zerumbet EO, which was used in therapeutic baths. We observed anesthetic effect of A. zerumbet EO in exposed fish with rapid sedation and recovery after exposure. Therapeutic baths with 300 mg L-1 of A. zerumbet EO had anthelmintic efficacy of 94% and low toxicity to fish. Just the levels of plasma glucose and total protein, and number of leukocytes, monocytes and neutrophils has a decreases in fish exposed to 300 mg L-1 de OE, and mild histopathological changes 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 of 30 min/day, for six consecutive days, for controlling and treating infections caused by monogeneans in the gills of C. macropomum.