How to Tackle the Number One Enemy of Litopenaeus vannamei - "Vibrio Disease"

In aquaculture, there is a harmful bacterium that causes a lot of headaches for farmers, known as Vibrio. During the farming process of shrimp, Vibrio can lead to severe conditions such as early-stage hepatopancreatic necrosis, empty intestines and stomachs, and sudden mortality. Whether in small ponds or larger outdoor ponds, high feed volumes and deteriorating water quality make these environments highly susceptible to Vibrio infections.

Types of Vibrio Infections in Shrimp:

Vibrio is a small, curved bacterium with a flagellum at its tail, which is anaerobic. The main pathogenic species for shrimp are: Vibrio alginolyticus, Vibrio parahaemolyticus, Vibrio harveyi, and Vibrio cholerae.

1.Vibrio alginolyticus: A Gram-negative bacterium, it can tolerate a pH range of 6-8.5 and salinity range of 5‰-50‰, but does not grow in freshwater. It can utilize monosaccharides or oligosaccharides, and forms yellow colonies larger than 2-3 mm on TCBS agar. Symptoms include ulcers, rotten gills, a red body appearance, empty intestines, and slight swelling in the hepatopancreas. The carapace may detach easily.

2.Vibrio parahaemolyticus: A Gram-negative bacterium that thrives at temperatures between 30-37°C, and tolerates pH levels from 6 to 8.5. It is a halophilic bacterium, multiplying rapidly at 20‰-30‰ salinity but ceases to grow below 5‰. It can utilize sucrose and lactose, forming blue-green colonies larger than 2-3 mm on TCBS agar. Symptoms include a cloudy white or slightly red body, enlarged and soft hepatopancreas, and partial atrophy in some infected shrimp. Infected shrimp may swim slowly or remain at the bottom of the pond, lose appetite, and have empty intestines and stomachs.

3.Non-O1 Vibrio cholerae: A Gram-negative bacterium that tolerates a pH range of 6-8.5 and grows in both freshwater and high salinity. It can utilize monosaccharides or oligosaccharides and forms yellow colonies larger than 2-3 mm on TCBS agar. Symptoms include sluggish movement, floating to the surface or rolling on its back, swollen eyes which darken and ulcerate, and the eventual whitening of the muscles. Death usually occurs within a week.

4.Vibrio harveyi: A Gram-negative bacterium that prefers temperatures around 37°C and tolerates pH levels from 5 to 9.5, with an optimal salinity range of 20‰-30‰. It does not grow in freshwater. It forms yellow colonies larger than 1-2 mm on TCBS agar. Early symptoms include reduced mobility, bottom-dwelling, and rolling with the water flow. Infected shrimp may refuse to feed and may not fluoresce in the early stages, but will emit fluorescence when near death or after dying.

Causes of Vibrio Infection in Shrimp:

1.Dead or decaying algae: After water quality worsens, an excess of algae die and accumulate at the bottom, creating foul-smelling organic matter that promotes Vibrio growth. Early detection and adjustment of water quality are essential to prevent this.

2.Excreted organic matter: Feces, leftover feed, and dead aquatic animals contribute to the accumulation of organic matter at the pond bottom, which provides a breeding ground for Vibrio bacteria.

3.Organic fertilizers: The use of raw organic fertilizers, such as chicken manure or organic compost, may contain high amounts of Vibrio bacteria that thrive during the fertilization process. These fertilizers should be treated with lime before use to eliminate any pathogens.

4.Zeolite and dolomite powders: Long-term use of zeolite and dolomite may compress harmful substances at the pond bottom, making it difficult to break them down, leading to high ammonia nitrogen, nitrite, and sulfide levels. These conditions deplete dissolved oxygen at the bottom and create an ideal breeding ground for Vibrio. It is recommended to minimize reliance on these substances.

5.Water source: Pollution of water sources in farming areas with high Vibrio levels can introduce the bacteria into shrimp ponds during water exchanges.

Conclusion: The main sources of Vibrio bacteria are decaying algae, excrement, organic fertilizers, feed, zeolite and dolomite powders, and other accumulated substances at the pond bottom. When these substances are not properly decomposed, they lead to increased chemical parameters, depletion of dissolved oxygen, and the proliferation of anaerobic bacteria in poor, foul-smelling pond environments, resulting in infection and disease in shrimp.

High-Density Shrimp Farming Measures for Preventing Vibrio Infections:

Preventive Measures: Shrimp farming and water management should be treated as an integrated system. In addition to managing water quality, it is crucial to maintain the shrimp’s health. Healthy shrimp are more resistant to diseases, including Vibrio infections. Therefore, during water treatment, internal health management must also be addressed.

High-Position Pond Shrimp Farming: In high-position ponds, the focus is on prevention. Maintaining water and substrate quality, adjusting algae, replacing water, and reducing organic matter can help lower the risk of Vibrio proliferation. Additionally, improving shrimp immunity by strengthening the care of their gastrointestinal, hepatic, and gill systems is essential to reduce the likelihood of infection.

If Vibrio levels are detected to be high, the following treatment plan can be implemented:

●Day 1: In the morning, apply “Aquaculture Multivitamins” to improve shrimp health. In the afternoon, use “Potassium monopersulfate compound” for disinfection.

●Day 2: In the morning, apply “Potassium monopersulfate compound” again (since Vibrio typically attaches to organic matter and pond surfaces).

●Day 3: Apply “Lactic Acid Bacteria” to replenish beneficial bacteria, which can rapidly establish an advantageous bacterial community in low-oxygen environments and inhibit Vibrio. Also, administer “Eucommia Yeast Polysaccharides” + “Lactic Acid Bacteria” (to lower pH and suppress Vibrio in the intestines) + “Aquaculture Multivitamins” in the feed, twice a day for 5-7 days to strengthen internal health.

Factory and Workshop Shrimp Farming: Regular monitoring and control of Vibrio are necessary, with periodic disinfection to prevent infection. After about 35 days of farming (when shrimp have finished stocking), disinfection can be done 7-10 days after shrimp start feeding, using mild disinfectants such as “Potassium monopersulfate compound” or “Chlorine Dioxide.” After disinfection, beneficial bacteria like “Lactic Acid Bacteria” should be added to restore microbial balance.

Note on Vibrio Detection and Control: Vibrio detection should be conducted using TCBS agar. However, disinfection alone cannot effectively control Vibrio because disinfectants, like broad-spectrum antibiotics, kill both harmful and beneficial bacteria, potentially leading to an imbalance in the microbial ecosystem. This may even accelerate Vibrio growth. The focus should be on prevention, as Vibrio cannot be completely eradicated. Instead, modifying its environment to control its population is the best strategy.

Preventing Vibrio involves regular monitoring and early intervention before Vibrio numbers reach dangerous levels, as bacteria can proliferate rapidly, leading to disease outbreaks.