EHP in Shrimp: Symptoms, Testing and How to Keep It Out

What Is EHP in Shrimp?

EHP in shrimp refers to infection by Enterocytozoon hepatopenaei, a microsporidian parasite that lives inside the tubule epithelial cells of the shrimp's hepatopancreas — the organ responsible for digestion and nutrient storage. Unlike White Spot Syndrome Virus or AHPND, EHP rarely kills shrimp directly. Instead, it damages the cells that absorb nutrients from feed, so infected shrimp keep eating but stop converting that feed into growth, leaving the pond with slow, uneven-sized shrimp at harvest even though the mortality count looks normal.

This is exactly what makes EHP in shrimp so costly and so easy to miss. A farmer checking daily mortality sees nothing alarming, while the pond quietly falls weeks behind its expected growth curve. EHP has been widely detected across Indian vannamei culture — Andhra Pradesh, Tamil Nadu, West Bengal, and Gujarat farms have all reported it — and it is now considered one of the most economically damaging pathogens in the industry precisely because it does not announce itself with a mortality spike.

Symptoms and Signs of EHP Infection

EHP does not have a single unmistakable symptom the way WSSV's white shell spots do. It shows up as a cluster of growth and performance problems that, together, should push a farmer toward testing rather than waiting.

• Stunted or highly uneven growth within the same pond — some shrimp reach normal size while others lag well behind despite equal feed access
• Poor feed conversion ratio (FCR) that keeps climbing even when feeding management looks correct on paper
• Soft shell or delayed moulting cycles, since nutrient absorption is impaired
• Pale or shrunken hepatopancreas on close inspection, though this sign overlaps with other hepatopancreas diseases and is not conclusive on its own
• Normal or only mildly elevated daily mortality — this is the biggest diagnostic trap, since farmers often rule out disease because shrimp are not dying
• Frequent co-occurrence with white feces disease and running mortality syndrome, since EHP-weakened shrimp are more vulnerable to secondary Vibrio infection

How EHP Spreads Into a Pond

EHP spreads mainly through direct transmission rather than through the water column alone, which is what makes hatchery and pond-prep discipline the highest-leverage control points.

• Infected post-larvae (PL) from a hatchery that has not screened broodstock or PL batches for EHP by PCR before sale
• Contaminated pond bottoms from a previous EHP-positive crop that was not fully dried and cleaned between cycles
• Spore-contaminated shared equipment, nets, or vehicles moving between infected and clean ponds
• Live feed organisms such as Artemia or polychaetes carrying EHP spores into broodstock or larval rearing systems
• Water exchange with an EHP-positive source pond or canal without adequate filtration or disinfection
• Cannibalism of infected shrimp tissue within the same pond, which recycles spores back into the population

Testing for EHP: PCR and What It Tells You

EHP cannot be confirmed by visual inspection alone — the hepatopancreas changes it causes overlap with other conditions, so laboratory testing is the only reliable diagnosis. PCR (polymerase chain reaction) testing targeting the EHP spore wall protein gene is the standard method, and most state fisheries labs and private aquaculture diagnostic labs across India now offer it.

A few practical points make PCR testing more useful rather than just a formality. Test PL batches before stocking, not after — this is the single point where a positive result still gives you a real choice (reject the batch) rather than a diagnosis after the money is already in the water. During grow-out, test hepatopancreas samples as soon as uneven growth or rising FCR appears, rather than waiting for a scheduled health check, since EHP load and its effect on growth compound over time. A negative PCR result on a small sample does not fully rule out a low-level infection, so repeat testing is worth it if growth problems persist without another explanation.

Prevention: Keeping EHP Out of Your Pond

There is no approved treatment that clears an active EHP infection from shrimp — management is entirely about prevention and containment. The good news is that EHP's transmission routes are well understood, so the prevention steps are specific rather than generic.

• Source PL only from hatcheries that PCR-screen broodstock and every PL batch for EHP — this is the highest-leverage single decision a farmer makes before a crop even starts
• Fully dry and disinfect the pond bottom between crops, including areas under aerators where sludge concentrates, since EHP spores can persist in bottom soil
• Avoid reusing water from an EHP-positive pond without treatment, and where possible use a separate water source or reservoir pond with filtration
• Disinfect nets, boots, and shared equipment between ponds, especially when moving from a suspect or positive pond to a clean one
• Screen and disinfect live feed inputs (Artemia, polychaetes) used in hatchery and broodstock systems
• Remove and properly dispose of dead or moribund shrimp promptly rather than leaving them for cannibalism, which recycles spore load back into the pond

EHP vs Other Vannamei Growth and Mortality Problems

EHP is frequently confused with, or masked by, other vannamei conditions because several share a damaged hepatopancreas as a common thread. Telling them apart quickly changes what you do next.

• EHP alone: slow, uneven growth and rising FCR with normal or near-normal daily mortality — the biggest tell is that shrimp are underperforming, not dying
• Running mortality syndrome (RMS): continuous low daily mortality (0.5–2% per day), very often EHP-positive on testing, but with visible daily deaths that pure EHP infection does not usually cause on its own — see our guide on running mortality syndrome in vannamei
• White feces disease (WFD): visible white faecal strings on the pond surface from Vibrio or gregarine damage to the hepatopancreas, a different primary cause though it can occur alongside EHP in stressed ponds
• AHPND/EMS: sudden, severe mortality in the first 30–35 days with an empty, atrophied hepatopancreas — much faster onset and far more dramatic than EHP's slow drag on growth

Why Water Quality Monitoring Matters Even With EHP

Continuous water quality monitoring does not remove EHP spores from a pond or a hatchery — no sensor can do that. What it does is reduce the additional stress load on shrimp that are already fighting an EHP infection, and it removes one of the two ingredients most commonly needed for EHP-positive ponds to tip into running mortality syndrome or a secondary Vibrio outbreak.

Our IoT monitoring system for shrimp hatcheries tracks dissolved oxygen, ammonia, pH, and temperature around the clock and alerts you the moment a parameter drifts outside a safe range, so hatchery and grow-out stress gets corrected in hours rather than discovered on the next round check. For the specific safe ranges to hold at each life stage, see our guide on vannamei water quality parameters by stage.

If a batch or pond has already tested EHP-positive, pair tighter water quality control with the PL screening and biosecurity steps above — monitoring reduces how badly a positive result plays out, but it is not a substitute for keeping EHP out of the hatchery in the first place.

Don't Let EHP Quietly Eat Into Your Harvest Weight

EHP is dangerous precisely because it does not look like an emergency. There is no mass die-off to force a decision — just weeks of slower growth, higher FCR, and a harvest that comes in lighter than the culture period should have produced. PCR-screening PL before stocking, disinfecting ponds and equipment between crops, and testing early when growth turns uneven are the three levers that matter most.

If you want to talk through PL screening practices, hatchery biosecurity, or setting up continuous water quality monitoring for your ponds, book a meeting with the MD. We work with shrimp farmers remotely across India.