Immunomodulatory Potency of Eclipta alba (Bhringaraj) Leaf Extract in Heteropneustes fossilis against Oomycete Pathogen, Aphanomyces invadans

Abstract

Aphanomyces invadans is an aquatic oomycete pathogen and the causative agent of epizootic ulcerative syndrome (EUS) in fresh and brackish water fish, which is responsible for severe mortalities and economic losses in aquaculture. Therefore, there is an urgent need to develop anti-infective strategies to control EUS. An Oomycetes, a fungus-like eukaryotic microorganism, and a susceptible species, i.e., Heteropneustes fossilis, are used to establish whether an Eclipta alba leaf extract is effective against the EUS-causing A. invadans. We found that treatment with methanolic leaf extract, at concentrations between 50–100 ppm (T4–T6), protects the H. fossilis fingerlings against A. invadans infection. These optimum concentrations induced anti-stress and antioxidative response in fish, marked by a significant decrease in cortisol and elevated levels of superoxide dismutase (SOD) and catalase (CAT) levels in treated animals, as compared with the controls. We further demonstrated that the A. invadans-protective effect of methanolic leaf extract was caused by its immunomodulatory effect and is linked to the enhanced survival of fingerlings. The analysis of non-specific and specific immune factors confirms that methanolic leaf extract-induced HSP70, HSP90 and IgM levels mediate the survival of H. fossilis fingerlings against A. invadans infection. Taken together, our study provides evidence that the generation of anti-stress and antioxidative responses, as well as humoral immunity, may play a role in protecting H. fossilis fingerlings against A. invadans infection. It is probable that E. alba methanolic leaf extract treatment might become part of a holistic strategy to control EUS in fish species.

Microbial inoculums improve growth and health of Heteropneustes fossilis via biofloc-driven aquaculture

“…We also explored other strategies to avoid microbial competition. Experiments were designed to investigate whether the assigned properties of individual microbial species in microbial consortium is hampered or not [ 1 , 18 ]. The study highlighted microbial species that don’t inhibit the growth and beneficial roles of other species and acts synergistically to improve the biofloc and health of cultured host animals.…”

“…Following the manufacturer’s protocol, the assay was performed and final OD value was taken in microplate reader at 450 nm. All assay kits were previously used for the biochemical indices and immune-stress responses analysis of serum in fish models [ 18 , 50 ].…”

“…In Southeast Asian countries, stinging catfish ( Heteropneustes fossilis ) is a well-known indigenous farmed catfish species, having several health benefiting properties [ 17 ]. With high demand, intensification and commercialisation of indigenous catfish aquaculture, farmers are frequently facing disease outbreaks and heavy mortalities due to microbial infections [ 18 ]. In case of H. fossilis , the proliferation of pathogenic and opportunistic microorganisms lead to decreased growth and food utilisation, and in many instances, massive mortality rates [ 19 ].…”

Aeromonas veronii Is a Lethal Pathogen Isolated from Gut of Infected Labeo rohita: Molecular Insight to Understand the Bacterial Virulence and Its Induced Host Immunity

“…The East Medinipur district is considered the hub of aquaculture in West Bengal, India, which accounts for the largest production of Indian Major Carp, including L. rohita [1]. However" due to the global demand increase, the pressure for intensification and further expansion of aquaculture has created many problems, including scarcity of natural resources, increased environmental pollution and losses due to disease outbreaks [1,7,8]. Disease outbreaks caused by microbial pathogens, considered the primary cause of production loss in fish farming, have moved to the forefront in recent years and brought socio-economic and environmental unsustainability to the aquaculture industry [9,10].…”

“…Among the various known pathogenic bacteria, Aeromonas veronii is a Gram-negative bacterium from the family Aeromonadaceae that has been frequently discovered in water, soil and food [1,[7][8][9][10]. A. veronii is known for causing pandemics and epidemics in Among the various known pathogenic bacteria, Aeromonas veronii is a Gram-neg bacterium from the family Aeromonadaceae that has been frequently discovered in w soil and food [1,[7][8][9][10].…”