1.What is EHP?
EHP stands for Enterocytozoon hepatopenaei, an intracellular parasite approximately 1 micron in size. It resides in the epithelial cells of the shrimp’s hepatopancreatic tubules. This parasite cannot generate its own energy and must extract it from host cells, impairing hepatopancreas function and severely affecting the shrimp’s digestion and nutrient absorption processes. EHP spores have a hard chitinous shell and can survive in water for 6–12 months while remaining infectious.
EHP has a relatively simple life cycle, consisting of only two stages: spores and meronts (the replication stage inside the host).
EHP Pathogenesis Mechanism:
- In the hepatopancreas, EHP deploys a polar tube to penetrate the host cell membrane and inject its infective material (sporoplasm).
- It rapidly replicates, forming inclusion bodies that disrupt normal cell functions.
- When the infected cell bursts, spores spread to adjacent cells and into the environment. A single spore can multiply into 1,000 within just one week.
2. Signs of EHP Infection in Shrimp
Shrimp infected with EHP often show no clear symptoms when young, and even mature shrimp may not exhibit definitive signs. However, the following are commonly observed in practice:
- Slow growth, stunting, and uneven size distribution within the population (after about 25 days, shrimp in the same pond may vary by 5–7 sizes).
- Possibly soft shells and darker-than-normal coloration.
- Reduced or complete loss of appetite.
- Shrinking or discolored hepatopancreas with pale or patchy coloration.
- Possible white feces syndrome due to weakened immunity and increased vulnerability to opportunistic pathogens.
- Weak, lethargic swimming and occasional scattered mortality.
3. Causes of EHP Infection
- Vertical transmission: from infected broodstock to post-larvae.
- Horizontal transmission: through feces, carcasses of infected shrimp, pond water, or contaminated feed.
4. Preventive Measures for EHP
Currently, there is no effective treatment for EHP. Therefore, proactive prevention is critical:
- Choose high-quality post-larvae from reputable sources with clear origin, and perform PCR testing before stocking.
- Disinfect ponds and equipment with highly active agents such as potassium permanganate, lime, hydrogen peroxide, and specialized high-potency products like Kill Faster, WiikonC, and Anti Septic from Truong Hai Tien.
- Strictly manage water sources and maintain good water quality to avoid pond bottom pollution. Use probiotics to enhance beneficial microbial populations in the environment, such as BZT New, Neo Bio, or high-density probiotics like Vibrix and TPD Control.
- Most importantly, boost shrimp resistance, hepatopancreas function, and immune mechanisms:
- Supplement anti-stress vitamins like Vitamin C – C Pak, and multivitamins like Miavita Gold.
- Support hepatopancreas function with herbal products like Cyto-EHP, Best Ga, and Herbal Aqua.
- Enhance gut health and liver function with Beta-glucans, probiotics, and nutrient absorption boosters like Liver Sure, Optipro, and Neoplus.
5. Conclusion
EHP is a significant threat to the aquaculture industry. Early detection and proper preventive measures are essential to minimizing damage, protecting shrimp yield and quality, and ensuring sustainable profitability for shrimp farmers.
