EHP (Enterocytozoon hepatopanaei) has been known for a long time (described by Tourtip in 2009), but recently it has been recognized as a major threat to the shrimp farming. EHP causes slow growth disease, although the mortality rate is low, it seriously affects the productivity of shrimp farming.
OVERVIEW OF EHP
Classify
Kingdom: Fungi
Phylum: Microspora (Sprague, 1977)
Class: Microsporea (Delphy, 1963)
Order: Microsporida (Balbiani, 1882)
Family: Enterocytozoonidae (Cali and Owen, 1990)
Genus: Enterocytozoon (Desportes et al., 1985)
Species: hepatopenaei (Tourtip et al. 2009)
As they share the same origin with fungi, they have the characteristic of reproduction and spreading through spores.
Form and structure
Structure of EHP
EHP does not have organelles that generate energy (mitochondria or chloroplasts). Therefore, EHP can only use energy from the host cell. They are obligatory intracellular parasites.
EHP spores have a thick cellwall, which allows them to survive in harsh conditions. Spores in feces or dry shrimp carcasses can survive up to 6 months, and even up to 1 year if in water, and still have the potential to cause disease.
Modes of transmission
- Shrimp in the same pond can infect each other through the release of feces or by eating dead conspecifics.
- Contaminated outside water sources are also one of the main causes of infection in the farming system.
- Broodstock shrimp can also transmit EHP to their nauplius.
- Shrimp can also become infected with EHP from intermediate hosts such as some small crustaceans, bivalves, etc.
- It should be noted that EHP can infect shrimp at all stages of development and at various salinity levels.
Signs of disease
Shrimp infected with EHP do not have any specific signs when they are small. Even when they are mature, there are no definitive signs to confirm that the shrimp is infected with EHP. The following are some common signs of EHP infection observed in reality:
- Shrimp size is not uniform (one pond can have 5-7 different sizes).
- Shrimp shell is slim, dark color, thin intestine.
- The hepatopancreas is uneven in size and color.
- Not eating or feeding abnormally.
- Shrimp die sporadically, a few each day.
- Associated with white feces syndrome.
- If the shrimp has patchy muscle discolouration, it is not due to EHP, but due to two other microsporidian parasites called Agmasoma penaei and Thelohania duorara, which are parasites on shrimp muscle tissue.
Shrimp infected with EHP
The lifecycle of EHP
The lifecycle of EHP is quite simple, with only 2 forms: spores and meronts (developmental and replicating stage inside the host). When entering the shrimp's body, they begin to infect the hepatopancreas, extend the polar filaments outside, penetrate the hepatopancreatic tubule cell membrane, transmit their genetic material inside the cell, replicate, and form new spores. They break open the cell and release outside, continuing to infect other cells. Within a week, one spore can produce up to 1000 new spores.
EHP spores push the polar filaments out
The hepatopancreas are destroyed, gradually peeling off, severely impairing the function of the hepatopancreas. Additionally, during the infection period, shrimp are more susceptible to opportunistic pathogens such as Vibrio bacteria or viruses.
Illustrate the life cycle of EHP
Diagnosis
As mentioned earlier, due to the non-specific clinical signs of EHP-infected shrimp, it cannot be diagnosed at the pond. Currently, there are several methods to detect EHP in shrimp, including:
- Microscopic examination of samples of shrimp hepatopancreas under a microscope, with a magnification of 100x or higher. This method is easy to perform and cost-effective.
- Histological examination of hepatopancreas samples. It has higher accuracy but is more difficult to perform and requires various types of chemicals and dyes.
- Molecular biology methods: PCR, nested PCR or real-time PCR. These methods have a high degree of reliability but are expensive to perform.
Currently, Than Vuong provides EHP diagnosis services to customers using the microscopic examination method, helping to screen and provide customers with a more visual understanding of the disease status in the pond.
Than Vuong's staff is professionally and methodically trained in microscopy EHP screening
The harmful effects of EHP
EHP infiltrates and attacks the hepatopancreatic tubule cells, causing a decline in the digestive and immune abilities of shrimp, making them lack the nutrients needed to molt and grow. Weakened shrimp are more susceptible to other disease-causing factors, and the progression of the disease is prolonged, causing sporadic shrimp mortality and increased FCR, which affects the productivity of shrimp farming.
EHP is also considered one of the causes of white feces syndrome (WFS). In white feces samples, a large number of EHP spores have been identified. Hepatopancreatic cells die and peel off into the gut, causing it to turn white. Of course, when shrimp suffer from white feces syndrome (WFS), they are already infected with many pathogens, but the presence of EHP in their bodies is a warning sign that they are highly susceptible to white feces syndrome in the future if appropriate interventions are not taken.
Furthermore, the gut microbiome of EHP-infected shrimp is significantly different from that of healthy shrimp. When EHP infiltrates, the abundance of the hepatopancreatic and gut microbiome decreases significantly. Along with this, there is an increase in disease-causing bacterial groups from the Vibrio, Aquimarina, and Leadbetterella genera. Beneficial bacterial groups are replaced during EHP infection, such as Bacteroides, Pseudomonas, Acinetobacter, Delftia, Agrobacterium, Achromobacter, Comamonas, as well as species belonging to the Bacillaceae family. This change in gut bacterial is a precursor to the progression of white feces syndrome (WFS).
Illustrating the change of shrimp intestinal microbiome after EHP infection for 30 days. Gray: EHP spores. Blue: Beneficial bacteria. Red: Harmful bacteria
The key to controlling EHP is to always keep the shrimp healthy. When shrimp have good immunity and growth, they can easily resist the effects of EHP as well as effectively combat other opportunistic pathogens from the environment.
7 WAYS TO PREVENT AND CONTROL EHP
1. Water treatment:
- Incoming water is filtered through several settling ponds, with a long settling time.
- At the end of the settling system, the water is treated with a dose of 3-5 ppm of potassium permanganate (KMnO4).
- The water for the pond is ready to be disinfected with 20 ppm chlorine and allowed to rest for a long period (5-10 days) before being supplied to the farming pond.
- For ponds that were previously infected with EHP, they should be thoroughly cleaned and left to dry for 10-15 days before starting a new crop. A 3% NaOH or 1% KOH solution should be sprayed onto the surface of the pond to increase the pH to above 10, which stimulates EHP spore germination. Germinated spores without a host will quickly die and cannot continue to spread the infection. Tools and equipment from previous farming cycles should also be soaked in the above solutions for 12 hours.
Typical farming model. Water has time to settle through many ponds before being supplied to ready ponds. Disinfect with Chlorine and store water alternately in 2 ponds ready to be supplied to the pond
2. Selecting post larvae
- Choose post larvae from reputable sources, and check for EHP disease-free status before introducing them to the farm.
- Choose larger post-larvae (post 12-13) for more reliable and safer EHP testing results.
3. Solution for nursery
- Moderate density (600 - 800) in large ponds (1000 m3 or more), with initial high water level (1.2 m).
- Restrict water exchange during the post-larval stage to avoid EHP infection from external sources. Only use siphoning and water top-up to compensate for water loss.
- Use strong probiotic products such as SOILMAX or LALSEA BIOREM daily to maintain water quality.
4. Regulates immunity and enhances digestive function
Lalpack Immune – Lalpack Probio
- Immune system regulation of shrimp using a special yeast system.
- Improved disease resistance, digestive and feed absorption function.
- Balanced gut microflora, controlled pathogenic microorganisms and toxin elimination, and enhanced gut health.
- Dosage: LALPACK IMMUNE 15g/kg and LALPACK PROBIO 15g/kg feed. To be used daily.
Herb Guard
- Detoxify the hepatopancreatic and restore its function as well as damaged cells.
- Prevent and control pathogens attacking the hepatopancreatic.
- Function as a prebiotic, providing nutrients for the growth of gut microbiota.
- Dosage: 15 ml/kg of feed. Use daily.
Before and after using HERB GUARD and LALPACK IMMUNE for 5 days. Before: the tubular cells of the hepatopancreas were damaged, contracted, and degenerated gradually. After: The cells were thicker, restored their shape and function. The amount of lipid stored in the tubular cells of the hepatopancreas also increased
Pro Gut – AquaMos
- Reduce the number of EHP spores in the shrimp's body by adhering to and excreting the pathogen out.
- Stimulate the immune system, enhancing the shrimp's resistance to opportunistic pathogens.
- Protect the intestinal mucosa, strengthen the beneficial microbiota in the gut, create a healthy microbiome in the gut and hepatopancreas, and prevent the microbiome degradation caused by EHP.
- Dosage: AQUAMOS 10g/kg of feed, PRO GUT 10g/kg of feed. Use daily.
The diversity of the gut microbiota increased after feeding PROGUT 5g/kg of feed per day
5. Concentrated nutritional supplement helps shrimp to be healthy and resistant to diseases
Canforta – QuickShell Gold
- Provides concentrated nutrition to promote fast growth of shrimp.
- Ensures sufficient nutrients to help shrimp resist stress, diseases, and unfavorable conditions.
- Helps shrimp molt at the right time and grow evenly.
- Dosage: CANFORTA 5 ml/kg. QUICKSHELL GOLD 5 ml/kg. Use daily. Double the dosage for shrimp over 45 days old.
6. Protect the gut health of shrimp
Pro Sur
- An alternative solution to antibiotics, controlling harmful bacteria thanks to selective antibacterial properties.
- Protecting the gut health of shrimp with a unique structure of medium and short chain fatty acids.
- Dosage: 5 ml/kg of feed. Use daily.
7. Management of pond water quality
SoilMax – Lalsea Biorem
- A powerful probiotic system that functions well in various environments.
- Lactic acid-producing bacteria strains inhibit the growth of harmful Vibrio bacteria.
- Decrease the number of fungal spores in pond water.
- Stabilize the microorganisms, algae, control toxic gases, and decompose organic matter, thereby stabilizing the environmental parameters and water quality.
- Dosage: SOILMAX 50g/1000 m3/day or LALSEA BIOREM 250g/3000 m3/day.
Bacterial diversity index in pond water improved after using SoilMax
References:
- Effect of Enterocytozoon hepatopenaei (EHP) infection on physiology, metabolism, immunity, and growth of Penaeus vannamei, T. Sathish Kumar, P. Ezhil Praveena, T. Sivaramakrishnan, J. Joseph Sahaya Rajan, M. Makesh, K.P. Jithendran, 2022.
- The shrimp microsporidian Enterocytozoon hepatopenaei (EHP): Biology, pathology, diagnostics and control. J. Inverte. Pathol, Chaijarasphong, T., Munkongwongsiri, N., Stentiford, G.D., Aldama-Cano, D.J., Thansa, K., Flegel, T.W., Sritunyalucksana, K. and Itsathitphaisarn, O., 2020.
- The emerging pathogen Enterocytozoon hepatopenaei drives a degenerative cyclic pattern in the hepatopancreas microbiome of the shrimp (Penaeus vannamei), Jesús Antonio López-Carvallo, Roberto Cruz-Flores & Arun K. Dhar, 2022.
- Shrimp microsporidian EHP spores in culture water lose activity in 10 days or can be inactivated quickly with chlorine, Werawich Pattarayingsakul, Natthinee Munkongwongsiri, Siripong Thitamadee, Kallaya Sritunyalucksana, Diva J. Aldama-Cano, 2022.
