France.- Scientists at CIRAD and IRD are testing the use of medicinal plants as an alternative to antibiotics in fish farms. Between laboratory analyses and field research, this innovative work is aimed at limiting the global problem of antibiotic resistance and reviving traditional knowledge of small-scale family fish farming in Southeast Asia. Samira Sarter, a researcher at CIRAD, will present different approaches for a prudent use of antibiotics to the 2 500 participants at the AQUA 2018 international congress, to be held in Montpellier from 25 to 29 August.
“The goal of our research is to reduce the use of antibiotics in aquaculture in order to limit antibiotic resistance in bacteria” says Samira Sarter, head of the DIVA team (Ichthyological DIVersity and Aquaculture – ISEM joint research unit) and a researcher at CIRAD. She has been exploring the world of plants to this effect for more than 10 years. Plants are tested based on information gathered not only in the literature, but also in the field, initially in Madagascar, then in Southeast Asia.
From traditional knowledge…
In these parts of Asia, the cradles of aquaculture, the use of medicinal plants is common. This was revealed by an ethnobotanical survey conducted in partnership with IRD in fish farms in northern Vietnam. In total, 66% of the 280 fish farmers consulted use plants in their breeding ponds. Some 24 plant species are thus used to treat and prevent diseases, mainly bacterial and fungal. Leaves, flowers and roots, whether whole or chopped, are sometimes mixed into feed, but in most cases are simply placed in the ponds.
… to laboratory analyses
Back in their laboratory, the researchers studied the antibacterial properties of certain plants, such as may chang (Litsea cubeba). Three concentrations of L. cubeba leaf powder were added to feed in experimental carp fish farms for 21 days: 2, 4 and 8%, as well as a control group at 0%. The fish fed with 4 and 8% doses demonstrated a stronger immune system and, in particular, a higher survival rate after infection by the pathogenic bacteria Aeromonas hydrophila.
These investigations are highly innovative in global aquaculture research. “Our dual approach, combining ethnobotany and laboratory analyses, is relevant in terms of not only protecting traditional knowledge, but also demonstrating the effectiveness of medicinal plants in fish farming as a possible alternative to antibiotics”, says Samira Sarter.
Antibiotic resistance, a major global problem
Residues of these drugs in fish farms contribute to the serious problem of antibiotic resistance, especially given that aquaculture already supplies half of global consumption of aquatic animal products, and this ratio is expected to increase since fishing will remain, at best, stable over the coming decades.