EHP in Shrimp Farming: Symptoms, Risk Factors, Prevention & Management Guide

EHP in Shrimp Farming: Complete Guide

Enterocytozoon hepatopenaei (EHP) is a microsporidian parasite associated primarily with severe growth retardation and uneven growth in cultured shrimp. Unlike several major shrimp diseases that can produce rapid mortality, EHP can remain relatively difficult to detect because infected shrimp may survive while showing poor growth and reduced production performance.

For shrimp farmers, the major concern is not simply mortality. Delayed growth, size variation, poor feed utilization and extended culture duration can significantly affect farm economics.

1. What is EHP?

EHP stands for Enterocytozoon hepatopenaei, a microsporidian parasite that infects the hepatopancreas of shrimp.

The hepatopancreas plays an important role in digestion, nutrient absorption, metabolism and energy storage. EHP develops within hepatopancreatic cells and can interfere with normal physiological functions.

EHP is particularly important in intensive shrimp farming because infection can result in:

Slow growth

Severe size variation

Poor feed utilization

Delayed harvest

Increased production costs

Reduced final biomass

Lower profitability

Why is EHP a Serious Problem in Shrimp Farming?

One of the biggest challenges with EHP is that there may be no obvious clinical signs during the early stages.

A farmer may see:

“The shrimp are alive, feeding and the pond looks normal—but the shrimp are not growing uniformly.”

As the crop progresses, differences in shrimp size may become increasingly visible.

This can lead to:

EHP infection → hepatopancreas damage → impaired nutrient utilization → slow growth → size variation → prolonged culture → increased production cost

Main Symptoms of EHP in Shrimp

EHP does not have a single distinctive external symptom. Laboratory testing is important for confirmation.

Common signs associated with EHP include:

1. Slow growth

Shrimp may initially appear normal but gradually show poor growth compared with healthy shrimp.

1. Uneven size

One of the most important field observations is large size variation within the same pond.

You may find:

Large shrimp

Medium-sized shrimp

Very small shrimp

at the same time.

Reduced feed intake

Affected shrimp may show reduced feeding activity, although poor feeding can also have many other causes.

Delayed harvest

Because growth is slower, the farmer may need to extend the culture period to achieve the desired harvest size.

White feces

White fecal strings or floating white material can sometimes be observed in ponds associated with EHP, but white feces alone cannot be used to diagnose EHP. Other conditions can produce similar observations.

Hepatopancreas changes

Discoloration or abnormalities in the hepatopancreas may occur, but these signs are not sufficiently specific to confirm EHP.

Important:

Do not diagnose EHP based only on pond appearance or shrimp size variation.

EHP Transmission

EHP can spread through oral transmission.

Potential routes include:

Infected shrimp

Cannibalism

Contaminated water

Fecal material

Pond sediment

Infected or contaminated live feeds

Contaminated equipment

Movement of material between ponds

Major Risk Factors for EHP

Risk Factor 1: EHP-positive PL

Introducing infected post-larvae is one of the most important risks.

Always source PL from reliable hatcheries and request appropriate health screening.

NFDB recommends PCR testing of post-larvae before stocking and using EHP-free PL.

Risk Factor 2: Poor Pond Preparation

Previous crop residues, organic matter and contaminated sediment can contribute to disease risk.

Poorly cleaned pond bottoms are particularly concerning when a previous crop had suspected or confirmed EHP.

Risk Factor 3: Contaminated Water

Water can act as a vehicle for infectious material.

Untreated water entering a pond can introduce unwanted organisms and potential EHP sources.

Risk Factor 4: Cannibalism

Dead and weak shrimp can be consumed by healthy shrimp.

If infected shrimp are eaten, this may contribute to the recycling and spread of EHP spores within the pond.

Therefore:

Dead shrimp should be removed promptly.

Risk Factor 5: Contaminated Equipment

Equipment can potentially move infectious material from one pond to another.

Examples include:

Nets

Buckets

Sampling equipment

Boots

Harvesting equipment

Feeding equipment

Risk Factor 6: Infected Live Feed

Live feeds used in broodstock and hatchery operations can represent a biosecurity concern if they are contaminated.

Risk Factor 7: High Organic Load

Accumulated organic matter and sludge can complicate overall pond health management.

How is EHP Diagnosed?

Field observation can raise suspicion, but laboratory diagnosis is required for confirmation.

PCR Testing

PCR is widely used for detecting EHP.

Testing may include:

Conventional PCR

Nested PCR

Real-time PCR

Other diagnostic approaches can include:

Histopathology

In-situ hybridization

LAMP

When Should Farmers Test for EHP?

Testing should not be limited to situations where the pond is already showing severe problems.

Recommended monitoring points:

Before stocking

→ Test PL batches.

During nursery/rearing

→ Monitor growth and health.

During grow-out

→ Test when unexpected growth retardation or significant size variation develops.

When disease is suspected

→ Collect appropriate samples and send them to a qualified aquatic animal diagnostic laboratory.

EHP Sample Collection Checklist

For laboratory diagnosis, follow the laboratory's sample requirements.

The NFDB guidance indicates:

For PL:

100–200 live post-larvae

For juveniles:

3–5 live or moribund shrimp

Sample submission checklist

☐ Correct number of shrimp collected

☐ Samples are representative of the population

☐ Live samples maintained appropriately where required

☐ Sample properly labelled

☐ Pond number recorded

☐ Sampling date recorded

☐ Shrimp age recorded

☐ Average body weight recorded

☐ Growth history recorded

☐ Feed consumption recorded

☐ Previous disease history recorded

☐ Sample sent promptly to an appropriate laboratory

EHP Prevention: The Most Important Strategy

There is currently no established treatment that reliably eliminates an active EHP infection from shrimp during grow-out. Therefore, prevention and biosecurity are central to EHP management.

Think of EHP management as:

Clean Seed + Clean Water + Clean Pond + Clean Equipment + Strong Biosecurity + Continuous Monitoring

Step-by-Step EHP Prevention Program

Step 1: Select a Reliable Hatchery

Purchase PL only from reputable, registered hatcheries.

Ask for:

PL health records

Batch information

PCR screening information

Brood stock health status

Hatchery biosecurity practices

Do not select seed based only on price.

Step 2: PCR-Test the PL

Before stocking:

Collect representative PL samples → Send to diagnostic laboratory → Confirm EHP status → Stock only after satisfactory health verification.

NFDB specifically recommends PCR testing PL before stocking.

Step 3: Completely Drain the Previous Pond

After harvest:

Remove remaining water.

Drain the pond completely.

Remove accumulated sludge.

Clean pond corners.

Clean areas underneath aerators.

Remove dead organic material.

Clean drainage channels.

Step 4: Dry the Pond Bottom

Proper drying is an important part of pond preparation.

Sun-drying helps reduce residual organic matter and assists in preparing the soil for subsequent treatment.

For farms with a previous EHP history, pond preparation should be more rigorous.

Step 5: Treat Contaminated Pond Sediment Appropriately

For EHP-affected earthen ponds, Indian aquaculture guidance has recommended calcium oxide/quicklime treatment under controlled pond-preparation conditions.

NFDB guidance describes application of approximately 6 tonnes/ha, followed by incorporation into the upper 10–12 cm of soil, moistening to activate the lime, and allowing appropriate holding time before subsequent preparation

Important safety note

Lime treatment is not a universal “one-size-fits-all” prescription.

Application rates and procedures should be determined according to:

Pond soil condition

Previous crop history

Soil pH

Moisture condition

Pond type

Local aquaculture regulations

Technical advice

Do not apply large quantities of quicklime without proper technical guidance.

Step 6: Clean Farm Equipment

Create separate equipment wherever possible.

Equipment checklist

☐ Nets

☐ Buckets

☐ Sampling trays

☐ Boots

☐ Feed containers

☐ Water-testing equipment

☐ Harvesting equipment

☐ Aerator-related equipment

☐ Pumps and hoses

Step 7: Manage Water Carefully

Use the cleanest practical water source.

Where appropriate:

Use a reservoir system.

Filter incoming water.

Treat water according to the farm's biosecurity protocol.

Prevent entry of wild crustaceans.

Prevent cross-contamination between ponds.

Step 8: Control Wild Carriers

Prevent unwanted aquatic animals from entering culture ponds.

Examples include:

Wild shrimp

Other crustaceans

Unwanted aquatic animals

Use appropriate filtration and farm biosecurity measures.

Step 9: Avoid Cannibalism

Remove:

Dead shrimp

Moribund shrimp

Heavily affected animals where practical

This is important because cannibalism can contribute to oral transmission of EHP.

Step 10: Maintain Good Pond Bottom Conditions

Regularly monitor:

Sludge accumulation

Black soil

Organic matter

Water color

Hydrogen sulfide risk

Dissolved oxygen

Feed waste

Good pond-bottom management is part of broader disease prevention and can reduce conditions that worsen overall shrimp health.

**Step 11: Avoid Overfeeding

**

Overfeeding can increase:

Organic loading

Uneaten feed

Bottom sludge

Water-quality problems

Feed should be adjusted based on:

Shrimp biomass

Feeding response

Water quality

Weather

Dissolved oxygen

Shrimp health

CIBA guidance specifically recommends avoiding overfeeding when EHP is diagnosed.

Step 12: Monitor Growth Weekly

Don't rely only on feed consumption.

Record:

What to Do if EHP is Suspected During Culture?

Step 1 — Don't panic

Slow growth does not automatically mean EHP.

Other factors can cause poor growth, including:

Poor feed quality

Underfeeding

High stocking density

Low dissolved oxygen

Poor water quality

Poor pond bottom condition

Other pathogens

Environmental stress

Step 2 — Check growth data

Compare:

Current ABW

Previous ABW

Expected growth

Feed intake

FCR

Size distribution

Step 3 — Collect shrimp samples

Select representative shrimp and submit them to a qualified aquatic animal diagnostic laboratory.

Step 4 — Perform PCR testing

Use an appropriate laboratory diagnostic method.

Step 5 — Review farm management

Check:

☐ Seed source

☐ PL health testing

☐ Stocking density

☐ Feed quality

☐ Feed quantity

☐ Water quality

☐ Bottom condition

☐ Sludge accumulation

☐ Dead shrimp removal

☐ Equipment hygiene

☐ Water exchange practices

☐ Biosecurity

EHP Management During an Ongoing Crop

If EHP is confirmed, the objective should be containment and maintaining shrimp health, rather than searching for a quick cure.

Important management actions:

1. Maintain adequate dissolved oxygen

Avoid oxygen stress because stressed shrimp are more vulnerable to additional health problems.

1. Avoid overfeeding

Adjust feeding according to actual shrimp response.

1. Maintain good water quality

Closely monitor:

DO

pH

Alkalinity

Ammonia

Nitrite

Temperature

Salinity

1. Manage the pond bottom

Remove excessive sludge and organic matter wherever practical.

1. Minimize cannibalism

Remove dead or moribund shrimp promptly.

1. Monitor growth

Continue weekly sampling to understand whether the crop is progressing.

1. Investigate secondary problems

EHP-affected shrimp may be more vulnerable to additional health problems, so do not assume every new symptom is caused by EHP.

Is There a Medicine for EHP?

This is one of the most common questions asked by shrimp farmers.

The practical answer:

There is no universally accepted curative treatment that reliably eliminates EHP from infected shrimp during grow-out.

Farmers should be cautious about products marketed as guaranteed “EHP cures.”

Before using any product, verify:

Active ingredients

Regulatory status

Manufacturer claims

Independent evidence

Recommended dosage

Withdrawal requirements, if applicable

Advice from a qualified aquatic animal health professional

Pond Preparation After an EHP-Affected Crop

After harvest:

Step 1

Completely drain the pond.

Step 2

Remove dead shrimp and organic material.

Step 3

Remove accumulated sludge, especially heavily contaminated areas.

Step 4

Clean pond infrastructure.

Step 5

Dry the pond thoroughly.

Step 6

Apply an appropriate pond disinfection/liming protocol.

Step 7

Plough/incorporate treatment into soil where applicable.

Step 8

Allow sufficient holding/drying time.

Step 9

Prepare and treat incoming water appropriately.

Step 10

Clean and disinfect equipment.

Step 11

Verify biosecurity before restocking.

CIBA and NFDB guidance emphasize pond preparation, drying, disinfection/liming and use of EHP-free seed as important components of EHP control.

Complete EHP Prevention Checklist for Shrimp Farmers

Before Stocking

☐ Pond completely drained

☐ Previous crop residues removed

☐ Sludge removed

☐ Pond bottom dried

☐ Appropriate pond treatment completed

☐ Pond equipment cleaned

☐ Nets disinfected

☐ Reservoir prepared

☐ Incoming water treated appropriately

☐ Wild carriers excluded

☐ Hatchery selected carefully

☐ PL health records checked

☐ PL tested for EHP

☐ Stocking density planned

☐ Farm biosecurity protocol established

**During Culture

**

☐ Daily shrimp behaviour observation

☐ Daily feeding observation

☐ Daily DO monitoring

☐ Regular pH monitoring

☐ Regular alkalinity monitoring

☐ Regular ammonia/nitrite monitoring

☐ Weekly growth sampling

☐ Size variation monitored

☐ Feed adjusted according to response

☐ Excess feed avoided

☐ Dead shrimp removed

☐ Pond bottom monitored

☐ Sludge accumulation monitored

☐ Equipment movement between ponds controlled

☐ Suspicious growth problems investigated

**If EHP is Suspected

**

☐ Check feeding history

☐ Check growth records

☐ Measure size variation

☐ Review water-quality records

☐ Check pond bottom

☐ Check seed history

☐ Collect representative samples

☐ Send samples for PCR

☐ Record laboratory result

☐ Review biosecurity

☐ Avoid unverified “EHP cure” claims

☐ Plan post-harvest pond remediation

EHP vs Other Shrimp Problems

Golden Rules for EHP Management

Rule 1

Start with clean seed.

Rule 2

Test PL before stocking.

Rule 3

Never ignore unusual size variation.

Rule 4

Maintain strong farm biosecurity.

Rule 5

Prevent cross-contamination between ponds.

Rule 6

Keep pond bottoms clean.

Rule 7

Remove dead shrimp quickly.

Rule 8

Avoid unnecessary overfeeding.

Rule 9

Use laboratory diagnosis instead of guessing.

Rule 10

Focus on prevention rather than searching for a cure after infection becomes established.

Conclusion:

EHP is a growth and production problem as much as it is a disease problem.

The most effective approach is to prevent the pathogen from entering the farm and to reduce opportunities for transmission.

The EHP management strategy can be summarized as:

EHP-Screened PL → Proper Pond Preparation → Clean Water → Strong Biosecurity → Controlled Stocking → Good Feeding → Clean Pond Bottom → Continuous Growth Monitoring → Early PCR Diagnosis