VIBRIO SPP. – POTENTIAL OPPORTUNISTIC PATHOGEN IN SHRIMP POND

Vibrio overview

Vibrio belongs to the family Vibrionaceae, order Vibrionales, class Gammaproteobacteria, phylum Proteobacteria. General characteristics of bacteria belonging to the genus Vibrio: gram-negative, a straight rod or slightly bent in shape, 0.3-0.5 x 1.4-2.6 μm in size. They do not form spores and move with a single flagellum or many slender flagella. All of them are facultative anaerobes and are the predominant bacterial group in natural marine environments and estuaries; they exist mainly in the shrimp’s intestinal tract. Some species are also human and marine animal pathogens.

Vibrio spp. is an opportunistic group of bacteria, when adverse conditions occur (shrimp infection with viruses, fungi, parasites, changes in pond water environment, shrimp in shock), they will dominate to thrive and cause disease in shrimp and other animals living in the same environment. The virulence of the Vibrio spp species is also highly dependent on the resident microorganisms in the shrimp body and the conditions of the environment. Therefore, it is advisable to build a stable and safe living environment that does not harm each other between microorganisms and shrimp.

Some Vibrio species, such as V. anguillarum, V. ordalii, V. salmonicida, V. parahaemolyticus, V. harveyi, V. vulnificus, and others, can cause diseases in aquatic animals.

For fish, Vibrio spp. mainly causes bacteremia. For shrimp, Vibrio spp. causes luminous disease, red along the body, and a corrosive chitin peel. V.parahaemolyticus causes luminous disease in black tiger shrimp larvae, causing early mortality in white-leg shrimp (EMS/AHPND). V.alginolyticus, V.harveyi, V.vulnificus, and V.anguillarum, causing red body disease in black tiger shrimp larvae, eroding shells in crustaceans, causing blood clot disease in crabs, causing molluscum contagiosum V. parahaemolyticus integrates with compatible virulent phages.

In addition, some strains can cause acute gastritis and cholera in humans when we eat seafood contaminated with pathogens.

Pathological signs when shrimp infected with Vibrio

Shrimps are in an abnormal state: floating on the head, swimming side by side, and swimming around pulling the flock around. Shrimp swim weak, lethargic, eat poorly, and stop eating.

Appear of red spots or black spots, corroded parts such as the body, thorax, and appendages of shrimp.

Shrimp have a change in shell color, turning red or green. Shrimp shell is soft and necrotic spots appear, the flesh is opaque, shrimp has prolonged white feces.

Diseased shrimp liver often appears in many states: Swollen, soft, pale in color, many cases of liver atrophy, and tough (EMS/AHPND infected shrimp)

Shrimp larvae and postlarvae showed a luminous phenomenon when infected with V.parahaemolyticus and V.harveyi.

Shrimp and fish infected with Vibrio will die completely, causing significant economic damage to farmers.

Measures to prevent disease of Vibrio spp.

For diseases caused by Vibrio infection, once the cause of the disease has been determined, some antibiotics that have been approved by the Ministry of Agriculture and Rural Development can be used. However, this will lead to residual antibiotic content in farmed aquatic animals, which leads to difficulties in selling and exporting to the market, affecting the health of consumers. Besides, when using antibiotics incorrectly can cause antibiotic resistance in aquatic animals leading to many consequences later. Therefore, diseases caused by Vibrio spp are mainly prevented:

• Pond preparation: treat the bottom, dry the pond, and disinfect the water thoroughly before stocking.
• Select a source of broodstock and shrimp seeds that are disease-free. (Check for disease by PCR method)
• Good management of water quality, algae density, and bottom siphon to reduce Vibrio spp. causes disease in the culture water environment. Regularly check the water parameters to take timely measures to reduce stress for shrimp.
• Regularly check and maintain the bacterial density in the pond water and culture environment at an appropriate threshold.
• Feed shrimp just enough, and choose a suitable clean food.
• Measures to add probiotics: Add beneficial microorganisms to the aquatic environment as well as to the body of shrimp and fish. Probiotics will help decompose excess organic matter in aquatic animals’ habitats, inhibiting the growth of opportunistic bacteria that cause disease. The advantages of this method are high efficiency, savings, safety, and environmental friendliness.

Proposed Solutions of Thai Nam Viet:

Thai Nam Viet specializes in providing high-quality and potent biological products. By competing with harmful Vibrio for nutrition and living space, creating inhibitors with harmful bacteria, and at the same time supplementing beneficial bacteria for the digestive system, Thai Nam Viet’s microbial strains are strongly effective in decomposing excess organic matter, creating a safe and stable living environment for farmed aquatic animals such as shrimp, fish, snails, frogs, as well as enhancing the animal’s immune system. Therefore, the use of probiotics will solve the target problems and ensure shrimp growth and health, limit damage and improve productivity.