Biological control compositions for preventing and treating infectious diseases in aquatic animals

Background

Aquaculture has become an essential component of global food production, supplying a significant portion of the world’s demand for fish and seafood. As the industry has intensified, the prevalence and impact of infectious diseases in farmed aquatic animals have grown, leading to substantial economic losses and threatening the sustainability of aquaculture operations. Diseases caused by bacterial and fungal pathogens, such as Edwardsiella ictaluri, Aeromonas hydrophila, and Saprolegnia, are particularly problematic in species like channel catfish and tilapia. The need for effective, safe, and sustainable disease control strategies is therefore critical to maintain productivity, ensure animal welfare, and support the continued growth of the aquaculture sector.

Current approaches to disease management in aquaculture largely rely on the use of antibiotics and chemical treatments. However, these methods present several significant challenges. The overuse and misuse of antibiotics have led to the emergence of resistant pathogens, posing risks not only to aquatic animal health but also to human health through the food chain and environmental contamination. Regulatory restrictions on antibiotic use are increasing, and the efficacy of available treatments is often limited by factors such as poor delivery, high costs, and adverse effects on non-target organisms and the environment. While probiotics and biological agents have shown promise, many commercially available strains lack robust evidence of efficacy, safety, or consistency in performance under field conditions. As a result, there remains an urgent need for alternative solutions that can reliably prevent and control infectious diseases in aquaculture without contributing to the growing problem of antimicrobial resistance.

Technology

This technology utilizes carefully selected spore-forming Bacillus bacteria, specifically B. subtilis and B. amyloliquefaciens, to prevent and treat bacterial and fungal infections in aquatic animals such as farmed fish and crustaceans. The Bacillus strains are identified by their unique 16S rRNA gene sequences and are incorporated into pelleted feed at concentrations of at least 10^6–10^7 CFU/g, or alternatively, applied directly to the aquatic environment. These strains function by producing antimicrobial compounds and through competitive exclusion, effectively inhibiting or killing a broad range of pathogens including Edwardsiella ictaluri, Aeromonas hydrophila, Flavobacterium columnare, and Saprolegnia. The technology encompasses protocols for preparing Bacillus spores, incorporating them into feed, and optimizing dosing regimens. It also allows for the use of single or multiple strains, and the compositions can be combined with other agents such as antibiotics or vaccines for enhanced disease control.

What differentiates this technology is its comprehensive approach to safety, efficacy, and practical application in aquaculture. The selected Bacillus strains are plasmid-free and susceptible to clinically important antibiotics, minimizing the risk of horizontal gene transfer and antibiotic resistance—a major concern with traditional antibiotic use. Extensive experimental validation demonstrates that these strains can colonize the fish intestine, persist after administration, and significantly reduce mortality in controlled challenge studies. The technology is further strengthened by detailed genetic characterization, genome sequencing, and the identification of antimicrobial compounds produced by the Bacillus strains. This multi-faceted solution not only addresses the limitations of conventional antibiotics but also supports sustainable and environmentally friendly aquaculture practices, offering a robust and scalable alternative for disease management in commercial settings.

Benefits

• Effective prevention and treatment of bacterial and fungal infections in aquatic animals
• Broad-spectrum antimicrobial activity against key aquaculture pathogens
• Safe use due to plasmid-free strains susceptible to antibiotics, reducing resistance risks
• Improved survival and reduced mortality in farmed fish and crustaceans
• Versatile application via feed additives or direct environmental treatment
• Supports sustainable and antibiotic-free aquaculture practices
• Stable spore-forming Bacillus strains capable of colonizing the aquatic animal gut
• Potential for combination with other agents (e.g., antibiotics, bacteriophages) for enhanced efficacy

Applications

• Aquaculture disease prevention in fish
• Probiotic feed additives for shrimp
• Pond water pathogen control
• Antimicrobial treatment for hatcheries

Additional info

This biological control system employs specific spore-forming Bacillus strains (e.g., B. subtilis, B. amyloliquefaciens), identified via 16S rRNA gene sequencing. Administered in feed (≥10^6 CFU/g) or aquatic environments, these agents produce antimicrobial compounds and utilize competitive exclusion to mitigate bacterial and fungal infections in aquatic animals. Selected strains are plasmid-free and antibiotic-susceptible, demonstrating efficacy in reducing disease mortality.