Shrimp Disease Diagnosis: Complete Guide for Farmers | When to Send Samples to a Lab

Shrimp Disease Diagnosis: When Should Farmers Send Samples to a Laboratory?

Disease problems can develop quickly in shrimp farming. A sudden reduction in feeding, unusual swimming behavior or unexpected mortality may be caused by poor water quality, bacterial infections, viral diseases, parasites or other environmental problems.

The challenge is that many shrimp diseases can show similar symptoms.

For this reason, farmers should not always try to identify a disease based only on what they see in the pond.

Laboratory diagnosis can help identify the possible cause and guide appropriate farm management decisions.

This guide explains when to send shrimp samples to a laboratory, how to collect samples correctly, what information to provide and what farmers should do after receiving the results.

Why Is Laboratory Diagnosis Important in Shrimp Farming?

A shrimp farmer may observe:

Reduced feed consumption

Weak shrimp

Empty gut

Slow growth

Abnormal swimming

Soft shell

Color changes

Lesions

Sudden mortality

But these signs alone may not tell you exactly what is happening.

For example, reduced feeding can result from:

Disease + low dissolved oxygen + poor water quality + temperature changes + stress + feed problems

Therefore, laboratory testing can provide additional evidence when the cause is unclear.

The basic principle is:

Observe → Record → Sample → Test → Interpret → Take Action

When Should Farmers Send Shrimp Samples to a Laboratory?

Farmers should consider laboratory testing when there is an unusual or unexplained change in shrimp health or pond performance.

1. Sudden Increase in Mortality

This is one of the strongest reasons to investigate immediately.

If mortality suddenly increases:

☐ Observe the affected pond

☐ Check water quality

☐ Check feeding behavior

☐ Collect appropriate shrimp samples

☐ Contact a qualified laboratory or aquatic animal-health professional

Do not wait for mortality to become severe before investigating.

2. Sudden Drop in Feed Consumption

A sudden reduction in feed intake can be an early warning sign.

Check:

Dissolved oxygen

Temperature

pH

Salinity

Ammonia

Nitrite

Weather conditions

Recent management changes

If water-quality conditions appear acceptable but feeding continues to decline, laboratory investigation may be appropriate.

3. Unusual Shrimp Behavior

Send samples for investigation when you observe unusual behavior such as:

Swimming near pond edges

Swimming at the surface

Weak swimming

Abnormal swimming patterns

Reduced response to feed

Unusual aggregation

Shrimp becoming inactive

These signs are not specific to one disease, so laboratory diagnosis may help determine the cause.

4. Physical Abnormalities

Farmers should investigate when they observe unusual physical changes such as:

Abnormal coloration

Lesions

Muscle abnormalities

Empty gut

Unusual hepatopancreas appearance

Shell abnormalities

Poor body condition

Unusual pigmentation

Take clear photographs and collect appropriate samples when necessary

5. Poor Growth or Uneven Growth

Laboratory testing is not required for every case of slow growth.

First check:

Feed quality

Feed management

Stocking density

Water quality

Temperature

Dissolved oxygen

Disease history

6. Repeated Problems in the Same Pond

If the same pond repeatedly experiences:

Mortality

Poor growth

Reduced feeding

Disease-like symptoms

Poor survival

farmers should consider a more detailed investigation.

Repeated problems may indicate an underlying issue involving pond conditions, biosecurity, seed health, water source or pathogens.

7. Before Major Management Decisions

Laboratory diagnosis can also be useful before making major disease-related decisions.

For example:

Do not automatically assume that every mortality problem is Vibrio.

A laboratory investigation may help distinguish between:

Bacterial problems

Viral diseases

Parasitic conditions

Environmental stress

Nutritional problems

Other causes

This can help farmers avoid unnecessary treatments.

Complete Step-by-Step Guide: How to Send Shrimp Samples to a Laboratory

Step 1: Observe the Problem

Before collecting samples, carefully observe the pond.

Record:

Date

Pond number

Stocking date

Shrimp age

Estimated biomass

Mortality

Feed consumption

Recent water exchange

Weather conditions

Recent treatments or product applications

Step 2: Check Water Quality First

Disease symptoms can sometimes be caused or worsened by environmental conditions.

Check, where relevant:

☐ Dissolved oxygen

☐ Temperature

☐ pH

☐ Salinity

☐ Alkalinity

☐ Ammonia

☐ Nitrite

☐ Water color

☐ Transparency

☐ Pond-bottom condition

Record the results.

Do not send a shrimp sample to the laboratory without recording the pond's environmental conditions whenever possible.

Step 3: Select the Right Shrimp

Sample selection is extremely important.

When possible, collect shrimp showing early or representative signs of the problem, rather than only dead and decomposed shrimp.

Good samples may include:

Weak but still living shrimp

Recently moribund shrimp

Shrimp showing early abnormal signs

Apparently affected shrimp

Representative healthy shrimp for comparison, when requested by the laboratory

Avoid:

❌ Severely decomposed shrimp

❌ Samples that have been sitting in the sun

❌ Damaged samples

❌ Samples contaminated with pond debris

Step 4: Collect Enough Samples

The required number depends on:

Type of suspected disease

Test method

Laboratory requirements

Sample type

Shrimp size

Always contact the laboratory before collecting samples when possible.

The laboratory can tell you:

Number of shrimp required

Whole shrimp or tissue required

Fresh or preserved sample

Container type

Temperature requirements

Transport method

Step 5: Handle Samples Carefully

Incorrect handling can affect test results.

Sample handling checklist

☐ Use clean equipment

☐ Avoid unnecessary handling

☐ Avoid contamination

☐ Keep samples cool as instructed

☐ Use appropriate containers

☐ Label every sample

☐ Follow the laboratory's preservation instructions

Do not freeze samples unless the laboratory specifically recommends freezing.

Different diagnostic tests require different sample-preservation methods.

Step 6: Label Every Sample

Every sample should be clearly identified.

Example:

Farm: ABC Shrimp Farm

Pond: Pond 3

Date: 07 October 2026

Shrimp Age: 55 DOC

Issue: Reduced feeding + mortality

Sample: Moribund shrimp.

Step 7: Complete the Laboratory Submission Form

Provide as much information as possible.

Farm information

☐ Farm name

☐ Location

☐ Contact details

☐ Pond number

Culture information

☐ Species

☐ Stocking date

☐ Stocking density

☐ Current age/DOC

☐ Estimated biomass

Disease information

☐ First date symptoms appeared

☐ Mortality level

☐ Feeding reduction

☐ Main symptoms

☐ Recent treatments

☐ Recent water-quality problems

Environmental information

☐ Temperature

☐ Dissolved oxygen

☐ pH

☐ Salinity

☐ Ammonia

☐ Nitrite

☐ Other relevant observations

Step 8: Transport the Sample Quickly

Time is important.

Samples should reach the laboratory as quickly as practical and according to the laboratory's instructions.

During transportation:

Maintain the recommended temperature.

Prevent overheating.

Avoid direct sunlight.

Prevent leakage.

Keep samples properly identified.

Follow the laboratory's transport instructions.

Step 9: Tell the Laboratory What You Suspect

Don't simply say:

"Shrimp are dying."

Give the laboratory a complete description.

For example:

"Shrimp are 55 DOC. Feeding dropped over the last three days. Mortality increased yesterday. Some shrimp are weak and showing abnormal swimming. Dissolved oxygen and other water-quality measurements are available."

This information gives the diagnostic team useful context.

Step 10: Ask Which Tests Are Appropriate

Depending on the symptoms, the laboratory may recommend different diagnostic methods.

Possible approaches can include:

PCR / Molecular Testing

Used to detect genetic material from specific pathogens.

Bacterial Testing

Can be used when bacterial disease is suspected and may include bacterial culture and identification.

Microscopic Examination

Can help identify certain parasites or other abnormalities.

Histopathology

Examines tissue structure and can provide evidence of disease-related changes.

Other Diagnostic Methods

The appropriate test depends on the suspected problem and the laboratory's capabilities.

The test should be selected based on the clinical and farm situation rather than ordering random tests.

Complete Shrimp Disease Sample-Collection Checklist

Before Sampling

☐ Observe shrimp behavior

☐ Record mortality

☐ Check feeding

☐ Check water quality

☐ Photograph symptoms

☐ Contact laboratory

☐ Confirm sample requirements

During Sampling

☐ Select representative shrimp

☐ Prefer live or freshly moribund shrimp when appropriate

☐ Avoid decomposed specimens

☐ Use clean equipment

☐ Avoid contamination

☐ Collect the required number of samples

Labeling

☐ Farm name

☐ Pond number

☐ Date

☐ Shrimp age

☐ Sample type

☐ Main symptoms

Documentation

☐ Mortality information

☐ Feeding information

☐ Water-quality data

☐ Recent treatments

☐ Recent management changes

☐ Previous disease history

Transportation

☐ Correct container

☐ Correct preservation method

☐ Appropriate temperature

☐ Avoid direct sunlight

☐ Prevent leakage

☐ Send promptly

When NOT to Wait for Laboratory Results

Some situations require immediate farm-management attention while diagnostic testing is underway.

For example, if shrimp mortality is increasing, farmers should not simply wait for a laboratory report before checking:

Dissolved oxygen → Water quality → Aeration → Feeding → Pond condition → Recent management changes

Laboratory testing and immediate farm management should happen in parallel.

Common Mistakes Farmers Should Avoid

Mistake 1: Sending Only Dead Shrimp

Dead shrimp may already be decomposed, making diagnosis difficult.

Mistake 2: Waiting Too Long

Samples collected several days after the first symptoms may not provide the best diagnostic information.

Mistake 3: Sending Unlabeled Samples

Always identify the pond and date.

Mistake 4: Ignoring Water Quality

A disease investigation should also consider environmental conditions.

Mistake 5: Assuming Every Mortality Is Vibrio

Different diseases and environmental problems can produce similar signs.

Mistake 6: Randomly Applying Products

Avoid changing several treatments at the same time without understanding the problem.

Mistake 7: Using Antibiotics Without Diagnosis

Antimicrobial treatment should be based on appropriate professional advice and applicable regulations.

Simple Decision Guide for Farmers

Shrimp look normal + feeding normal + mortality normal

➡ Continue routine monitoring.

Feeding decreases

➡ Check water quality and shrimp behavior.

Feeding decreases + unusual behavior

➡ Increase monitoring and consider diagnostic sampling.

Mortality starts increasing

➡ Check water quality immediately + collect appropriate samples.

Mortality continues or increases rapidly

➡ Send samples to a qualified laboratory and seek professional diagnostic support.

Laboratory confirms a pathogen

➡ Follow the recommended management and biosecurity response.

What Should Farmers Do After Receiving the Laboratory Report?

Receiving a laboratory report is not the final step.

Farmers should:

Understand what was detected.

Discuss the result with a qualified aquatic animal-health professional where appropriate.

Compare the result with pond symptoms.

Review water-quality records.

Review recent farm-management changes.

Strengthen biosecurity.

Monitor affected ponds closely.

Avoid unnecessary treatments.

Keep the report as part of the farm's health records.

Remember:

A laboratory result should be interpreted together with farm observations and environmental information.

Complete Shrimp Disease Diagnosis Checklist

🚨 Early Warning Signs

☐ Sudden mortality

☐ Reduced feeding

☐ Abnormal swimming

☐ Weak shrimp

☐ Empty gut

☐ Poor growth

☐ Abnormal color

☐ Visible lesions

☐ Unusual hepatopancreas appearance

☐ Repeated disease problems

💧 Water Quality

☐ Dissolved oxygen

☐ Temperature

☐ pH

☐ Salinity

☐ Alkalinity

☐ Ammonia

☐ Nitrite

☐ Water appearance

☐ Pond-bottom condition

🔬 Laboratory Sampling

☐ Contact laboratory

☐ Confirm sample requirements

☐ Select appropriate shrimp

☐ Avoid decomposed samples

☐ Use clean equipment

☐ Label samples

☐ Complete submission form

☐ Maintain recommended temperature

☐ Transport promptly

📋 Farm Information

☐ Pond number

☐ Shrimp age/DOC

☐ Stocking density

☐ Feed consumption

☐ Mortality history

☐ Water-quality records

☐ Recent treatments

☐ Recent weather events

☐ Previous disease history

🛡️ After Diagnosis

☐ Review laboratory report

☐ Consult appropriate professional

☐ Review farm conditions

☐ Strengthen biosecurity

☐ Monitor shrimp closely

☐ Record the diagnosis

☐ Avoid unnecessary treatment

☐ Continue water-quality monitoring

conclusion

Early diagnosis can save valuable time in shrimp farming.

Farmers should consider sending samples to a laboratory when they observe unexplained mortality, sudden feeding reduction, unusual shrimp behavior, physical abnormalities, persistent poor growth or repeated disease problems.

The best approach is:

Observe → Check Water Quality → Collect the Right Sample → Send to the Laboratory → Interpret the Result → Take Evidence-Based Action

Laboratory testing should not replace good farm management. Instead, it should work alongside daily observation, water-quality monitoring, biosecurity, proper feeding and good shrimp-health management.

The earlier an unusual problem is investigated, the better the opportunity to identify its cause and respond appropriately.