Immunomodulatory Effects of Mallotus japonicus Extract on Innate Immune Responses in HeteroTilapia buttikoferi Infected with Aeromonas hydrophila

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The intensive use of antibiotics in modern aquaculture has been linked to the emergence of multidrug resistance in human health. Despite continuous caution against such use by farmers, antibiotics serve as the primary means of disease control in aquaculture. In this study, we explore the potential of medicinal plant extracts as immunomodulant in enhancing the innate immune defense of a fish host, HeteroTilapia buttikoferi, infected with the prevalent fish pathogenic bacteria Aeromonas hydrophila. Our previous research reveals the bactericidal activity of the medicinal plant, Mallotus japonicus, against the pathogen, but its effectiveness as a prophylactic in enhancing host immune defense has not yet been investigated. Therefore, the objective of this study is to address this knowledge gap.By our findings, it was uncovered that the supplementation of the diethyl ether extract of the plant’s bark as an additive in the fish diet significantly improved the innate immune defense by upregulating the total levels of lysozyme, serum bactericidal activity, globulin and albumin levels, total protein, phagocytosis, respiratory burst activity and overall survival. A dose-dependent increase in immunological parameters was recorded, and this was in sharp contrast to the control group.These findings suggest that M. japonicus has the potential of use to enhance the innate immune defense of H. buttikoferi against the pervasive fish pathogenic bacteria, Aeromonas hydrophila. The improvements in immune parameters indicate the ability of M. japonicus extract to strengthen the hosts to combat bacterial infections.