Effects of ten traditional Chinese herbs on immune response and disease resistance of Sciaenops ocellatus (Actinopterygii: Perciformes: Sciaenidae)

Abstract

Background. Traditional Chinese herbs (TCHs) are widely used for improving non-specific immunity of fish in aquaculture. Possible effects of many important TCH on red drum, Sciaenops ocellatus (Linnaeus, 1766), have not been adequately studied. The aim of the presently reported study was to investigate the effects of ten TCH on selected immunological- and haematological responses of red drum. Materials and methods. >Ten TCH preparations, consisting of selected parts of plants and fungi, known in medicinal practice as: Astragalus membranaceus, fructus forsythiae, Polyporus umbellatus, Scutellaria baicalensis, Wolfiporia extensa, rhizoma coptidis, radix glycyrrhizae, flos lonicerae japonicae, isatidis radix, and bupleuri radix were used in the experiment. A dose of 10 g of each TCH was decocted and concentrated, then mixed with the diets (mixed diets) at ratio of 2%. After 28 days of feeding, the fish were infected with Vibrio splendidus and observed for 14 days for possible mortalities. Leukocyte phagocytic activity and lysozyme activity (LZM) were measured on days 0, 3, 7, 14, 21, 28, and 35. Relative percentage survival (RPS) of each TCH treatment was also investigated after the fish exposure to V. splendidus. Results. Red drum fed 2% doses of individual TCH extracts significantly (P < 0.05) increased its: phagocytic percentage (PP) (with the exception of flos lonicerae japonicae treatment), phagocytic index (PI) (with the exception of flos lonicerae japonicae- and bupleuri radix treatments), LZM (with the exception of Wolfiporia extensa treatment), and RPS (with the exception of P. umbellatus, Wolfiporia extensa-, radix glycyrrhizae-, flos lonicerae japonicae-, isatidis radix-, and bupleuri radix treatments). The indexes of PP, PI, and LZM, for all experimental groups, decreased quickly on day 35 (7 days after TCH diets were discontinued). On the other hand, PP values were significantly (P < 0.05) higher than in control (with the exception of flos lonicerae japonicae- and Wolfiporia extensa treatments). Also PI values were significantly higher (P < 0.05) than in control (with the exception of flos lonicerae japonicae-, Wolfiporia extensa-, and bupleuri radix treatments). LZM values exhibited no significant difference (P > 0.05) in all treatment groups compared with control. Most importantly, the A. membranaceus-, or S. baicalensis-, or fructus forsythiae-fed groups were significantly protected (P < 0.01) against V. splendidus challenge compared to control. RPS of A. membranaceus- and S. baicalensis groups were the highest, reaching 88.9% on day 28, followed by the fructus forsythiae group, whereas bupleuri radix- and Wolfiporia extensa treatments showed the lowest values. Conclusion. A. membranaceus, S. baicalensis, and fructus forsythiae were effective in preventing red drum from acquiring the disease while challenged by V. splendidus.

Keywords

• traditional Chinese herbs
• Sciaenops ocellatus
• Vi