Immunomodulatory roles of probiotics in aquaculture: mechanisms and applications for fish disease control

Abstract: The rapid intensification of global aquaculture has increased reliance on antibiotics, contributing to the emergence of antimicrobial resistance (AMR) and environmental degradation. Consequently, there is growing interest in sustainable alternatives such as probiotics, which function as “immunobiotics” to enhance host health and disease resistance. This review synthesizes current knowledge on the multifaceted roles of probiotics in aquaculture, with particular emphasis on the integrated “gut–mucus–immune–redox axis”. Probiotic taxa, notably Bacillus and Lactobacillus species, promote growth and feed efficiency through the secretion of digestive enzymes and the improvement of nutrient utilization, while also maintaining intestinal integrity via modulation of mucosal architecture, including goblet cell proliferation. At the molecular level, probiotics exert immunomodulatory effects by regulating the expression of immune related genes, including Toll-like receptors (TLRs), cytokines, and immunoglobulins, thereby enhancing both innate and adaptive immune responses. Additionally, probiotics contribute to disease control through quorum quenching mechanisms that interfere with pathogen communication and virulence. By integrating insights into strain-specific functionality and host–microbe interactions, this review highlights the potential of probiotics to replace conventional chemotherapeutics and supports a transition toward biologically driven, sustainable disease management strategies in aquaculture. 

Keywords: Probiotics, immunomodulation, gut microbiota, innate immunity, antimicrobial resistance (AMR)