Using Bacteriophage Therapy in Aquaculture to Control Shrimp Vibriosis

Last Updated: November 13, 2025

Estimated reading time: ~6 minutes

Word count: 1318

As antibiotic resistance grows in shrimp farming, scientists are turning to nature’s own bacterial predators: bacteriophages. This strategy, known as Bacteriophage Therapy in Aquaculture, involves using specific viruses that infect and kill pathogenic bacteria like Vibrio, offering a promising, eco-friendly alternative for disease control.

• Bacteriophages (or “phages”) are viruses that exclusively infect and kill bacteria.
• This therapy is highly specific, meaning it can target pathogenic Vibrio while leaving beneficial bacteria unharmed.
• Phages are a natural component of aquatic ecosystems and are considered safe for shrimp, humans, and the environment.
• Research focuses on isolating “lytic” phages, which cause the bacterial cell to burst, stopping the infection.

The Viral Solution: An Introduction to Bacteriophage Therapy in Aquaculture

In the ongoing battle against shrimp diseases, the failure of traditional antibiotics has created an urgent need for new solutions. Bacteriophage Therapy in Aquaculture has emerged as a leading candidate. This approach leverages bacteriophages—viruses that are the natural enemies of bacteria—to combat infections. By isolating phages that specifically target harmful pathogens like Vibrio harveyi, researchers can create “living antibiotics” that are both effective and environmentally sound. This article, based on a 2005 thesis on Vibrio control, explores the potential of this fascinating biological control method.

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What Are Bacteriophages and How Do They Work?

This section explains the fundamental biology of bacteriophages and their lytic life cycle, which is essential for therapy.

“Bacteriophages, and immunostimulants are the most promising and environmental friendly alternatives to antibiotics in controlling vibriosis in aquaculture systems” (R. G. R., 2005, p. 195).

Bacteriophages, often shortened to “phages,” are the most abundant life forms on Earth. They are viruses, but they cannot infect humans, animals, or plants; their specialization is absolute. Each phage type targets a specific bacterial species or even a specific strain. They work by injecting their genetic material into a host bacterium and hijacking its cellular machinery.

There are two main life cycles:

1. Lytic Cycle: This is the cycle used in phage therapy. The phage replicates rapidly inside the bacterium, assembling hundreds of new phage particles. It then releases enzymes that break open (lyse) the bacterial cell wall, destroying the bacterium and releasing the new phages to infect nearby bacteria.
2. Lysogenic Cycle: In this cycle, the phage DNA integrates into the bacterial chromosome and lies dormant, replicating along with the bacterium without killing it. This is generally not useful for therapy.
3. Sample Collection: Researchers collect water and sediment from shrimp ponds, especially those with a history of Vibriosis, as these areas are likely to have high concentrations of both *Vibrio* and their corresponding phages.
4. Enrichment: The samples are “baited” in the lab with cultures of the target pathogen (e.g., V. harveyi). This encourages the specific phages to multiply.
5. Plaque Assay: The enriched sample is filtered to remove bacteria and then added to a “lawn” of V. harveyi growing on an agar plate. Where a phage successfully kills bacteria, it creates a clear, circular zone called a “plaque.”
6. Purification: Phages from a single plaque are isolated and re-grown, ensuring a pure-strain “phage cocktail” that is highly effective against the pathogen.
7. Bacteriophage therapy is an eco-friendly alternative to antibiotics for controlling bacterial diseases in aquaculture.
8. Phages are viruses that are highly specific, targeting only their host bacteria (e.g., Vibrio harveyi) and leaving beneficial microbes untouched.
9. The lytic cycle is the mechanism used for therapy, where phages replicate inside bacteria and then burst (lyse) them.
10. Scientists isolate effective phages from the farm environment itself using enrichment and plaque assay techniques.
11. Studies confirm that phage therapy can significantly reduce mortality in shrimp larvae challenged with pathogenic Vibrio, demonstrating its in vivo effectiveness.
12. What is the primary mechanism of action in lytic phage therapy?
    a) The phage integrates its DNA into the bacterium’s chromosome and remains dormant.
    b) The phage hijacks the bacterium, replicates, and then lyses (bursts) the cell.
    c) The phage competitively excludes the bacterium from nutrients.
    d) The phage boosts the shrimp’s immune system.
    Correct Answer: b) The phage hijacks the bacterium, replicates, and then lyses (bursts) the cell. Explanation: The lytic cycle is defined by the replication and subsequent destruction of the host bacterial cell.
13. A clear zone on a “lawn” of bacteria infected with phages is called a:
    a) Colony
    b) Plaque
    c) Lysis zone
    d) Biofilm
    Correct Answer: b) Plaque. Explanation: A plaque is a visible, clear area on a bacterial lawn where phages have killed the bacteria.
14. What is the main advantage of phages over broad-spectrum antibiotics in aquaculture?
    a) They are cheaper to manufacture.
    b) They are highly specific and do not harm beneficial bacteria.
    c) They work against all types of viruses and fungi.
    d) They are easier to store in warm water.
    Correct Answer: b) They are highly specific and do not harm beneficial bacteria. Explanation: This specificity protects the shrimp’s gut microbiome and the pond’s microbial ecosystem.
15. Are bacteriophages safe for the shrimp?
    Yes. Phages are completely harmless to shrimp, plants, and humans because they can only infect their specific bacterial hosts.
16. Can bacteria become resistant to phages?
    Yes, bacteria can evolve resistance. However, phages also co-evolve, and new phages can be isolated to overcome this resistance, unlike static antibiotics.
17. What is a “phage cocktail”?
    This is a mixture of several different phage strains. It is often used in therapy to target multiple strains of a pathogen or to reduce the chance of resistance.
18. Is phage therapy used commercially?
    Yes, phage therapy is approved and used in food safety (e.g., on meat) and is increasingly being used in aquaculture and veterinary medicine as an antibiotic alternative.
19. NCBI: Bacteriophage Therapy to Control *Vibrio* Infections in Aquaculture
20. ScienceDirect: The role of bacteriophages in aquaculture: advantages, potential, and challenges