Introduction
Enterocytozoon hepatopenaei (EHP) has become one of the most persistent challenges in shrimp hatcheries and grow-out systems. While it doesn’t directly cause mortality, its impact on growth and uniformity makes it a silent profit-killer. Understanding how and when EHP enters the larval rearing tank (LRT) is critical for breaking its cycle.
How Does EHP Enter the LRT?
EHP spores can find their way into hatchery systems through multiple routes:
- Broodstock contamination → feces or wash water carrying spores
- Live feeds → polychaetes, artemia, or algae cultures harboring spores
- Water supply → untreated or poorly disinfected intake water
- Cross-contamination → nets, siphons, staff, or aerosols
- Tank residues → sludge, biofilms, or recycled effluent
When Does Infection Begin?
- Nauplii stage: No mouth → cannot ingest spores → not susceptible
- Zoea stage: Mouth opens → active feeding begins → spores can be ingested
- Mysis & PL stages: Feeding continues → higher risk of ingestion and infection
👉 The infection cycle starts only after the Zoea stage, when larvae begin feeding.
The Multiplication & Recycling Loop
- Inside the shrimp: EHP multiplies only in hepatopancreas epithelial cells
- Shedding: Infected cells release spores, which are excreted in feces
- Recycling: Spores in the tank are re-ingested by Zoea, Mysis, or PLs
- Amplification: Each new infection produces more spores, fueling the cycle
Why the LRT Becomes a “Factory” of EHP
While the real multiplication happens inside shrimp cells, the LRT environment acts as a recirculating reservoir:
- Spores shed into water and waste
- Larvae continuously re-ingest them
- Infection pressure rises exponentially
This is why an EHP-positive LRT can quickly become a high-risk amplification zone.
Key Takeaways
- EHP entry routes: broodstock, live feed, water, equipment, residues
- Infection starts only after Zoea (mouth opens)
- Multiplication occurs in hepatopancreas, not in water
- LRTs amplify infection through continuous recycling of spores
Final Word
EHP does not kill shrimp directly, but it silently kills the profitability of shrimp farming. Growth retardation, uneven sizes, and poor feed conversion all trace back to unchecked infection pressure.
The hatchery stage is the first line of defense. If spores are allowed to amplify in larval tanks, they will inevitably move downstream into nurseries and farms, multiplying the economic damage.
Breaking the EHP cycle requires strict biosecurity, proper feed and water disinfection, and effective waste management. Once spores establish in an LRT, the system can rapidly become a hotspot of infection, jeopardizing the entire batch.
Remember: biosecurity is always cheaper than recovery. A clean LRT is not just good practice; it is the foundation of sustainable hatchery success.