PURULENT HEPATORENAL DISEASE IN PANGASIUS: CAUSES, SYMPTOMS, TREATMENT, AND EFFECTIVE PREVENTION

Purulent hepatorenal disease is one of the most serious infectious diseases affecting pangasius (striped catfish), causing significant losses to Vietnam’s aquaculture industry.

The disease spreads rapidly, can occur at various growth stages of fish, and may significantly reduce productivity if not detected and treated promptly.

As pangasius farming continues to expand under intensive farming systems with high stocking densities, understanding purulent hepatorenal disease enables farmers to implement effective preventive measures, improve water quality management, and optimize fish health management.

This article provides comprehensive information about the causes, clinical signs, diagnosis, treatment, and biosecurity-based prevention of purulent hepatorenal disease.

What Is Purulent Hepatorenal Disease?

Purulent hepatorenal disease is a bacterial infection caused by Edwardsiella ictaluri. This bacterium can survive in pond water, bottom sediments, and spread rapidly under unfavorable farming conditions.

After entering the fish through the gills, skin, or digestive tract, the bacteria multiply in internal organs such as the liver, kidneys, spleen, and brain.

The infection forms small abscesses that damage tissues and impair the function of vital organs, gradually weakening the fish and eventually causing death if left untreated.

Today, the disease is commonly found in intensive pangasius farming areas, particularly during seasonal transitions or when water quality deteriorates.

Hepatorenal abscess, caused by the bacterium Edwardsiella ictaluri, spreads rapidly in intensive aquaculture ponds.

Causes of Purulent Hepatorenal Disease in Pangasius

Several factors contribute to disease outbreaks, including both the pathogen itself and environmental conditions.

Edwardsiella ictaluri

This bacterium is the direct cause of the disease. It can survive in:

Pond water
Bottom sediments
Carrier fish
Poorly sanitized farming equipment

Under favorable conditions, the bacteria multiply rapidly and spread throughout the entire fish population.

Poor Water Quality

Ponds containing excessive organic matter, uneaten feed, and accumulated waste provide an ideal environment for bacterial growth.

Environmental factors that increase disease risk include:

Low dissolved oxygen levels
High ammonia (NH₃) concentration
Elevated nitrite (NO₂⁻) levels
Sudden pH fluctuations

These conditions weaken the immune system of fish, making them more susceptible to infection.

High Stocking Density

Overcrowding increases competition for oxygen, feed, and space. Fish become stressed, allowing the bacteria to spread more quickly among individuals.

Weather Changes

Seasonal transitions, prolonged rainfall, and sudden temperature fluctuations reduce fish immunity and create favorable conditions for disease outbreaks.

Poor Nutritional Management

Low-quality feed, vitamin deficiencies, or overfeeding contribute to water pollution and negatively affect fish health.

Edwardsiella ictaluri bacteria are the direct cause of hepatorenal abscess disease in catfish.

Clinical Signs of Purulent Hepatorenal Disease

Early detection can significantly reduce economic losses.

External Symptoms

Farmers may observe:

Reduced feed intake or complete loss of appetite
Lethargic swimming behavior
Fish gathering near the water surface
Darkened body coloration
Slow response to external stimuli
Bulging or hemorrhagic eyes
Some fish swimming in circles due to nervous system damage

During severe outbreaks, fish mortality initially occurs sporadically before rapidly increasing.

Internal Symptoms

Necropsy of infected fish typically reveals:

White nodules on the liver
Small abscesses in the kidneys
Enlarged spleen
Hemorrhage in internal organs
Soft, fragile kidneys
Fluid accumulation in the abdominal cavity

These lesions are characteristic features that help distinguish purulent hepatorenal disease from other bacterial infections.

Disease Transmission

Purulent hepatorenal disease spreads primarily through:

Direct contact between infected and healthy fish
Contaminated water sources
Improperly disinfected equipment
Birds, animals, or humans carrying pathogens from other ponds
Infected fingerlings that show no obvious clinical signs

In high-density farming systems, the disease can spread rapidly throughout the pond.

Economic Impact

Without proper control, the disease can cause severe consequences.

Economic Losses

High mortality rates under unfavorable conditions
Increased treatment costs
Longer production cycles
Higher feed conversion ratio (FCR)
Reduced farm profitability

Reduced Market Quality

Infected fish often exhibit:

Slow growth
Poor overall health
Uneven body size
Lower market value due to inferior quality

Diagnosis of Purulent Hepatorenal Disease

Accurate diagnosis requires a combination of methods.

Observation of Clinical Signs

Monitor:

Swimming behavior
Feeding activity
Body coloration
Daily mortality rate

Internal Examination

Necropsy is essential for detecting characteristic abscesses in the liver and kidneys.

Laboratory Testing

When treatment is required, samples should be submitted to a diagnostic laboratory to identify the causative bacterium and determine its antimicrobial susceptibility.

This helps ensure appropriate treatment while reducing the risk of antimicrobial resistance.

Treatment of Purulent Hepatorenal Disease

Effective treatment should combine environmental management with proper fish care.

1. Improve Water Quality

This is the first and most important step.

Farmers should:

Monitor pH daily
Measure dissolved oxygen levels
Control ammonia (NH₃) and nitrite (NO₂⁻)
Replace water when appropriate
Remove bottom sludge regularly

2. Reduce Feeding

During disease outbreaks:

Reduce feeding rates
Avoid overfeeding
Remove uneaten feed

These measures help minimize water pollution.

3. Provide Nutritional Support

Supplements may include:

Vitamin C
Vitamin E
Minerals
Probiotics
Immunostimulants used according to the manufacturer’s recommendations

These products help improve immunity and support recovery.

4. Use Medications Under Professional Guidance

Antibiotics should only be administered under the supervision of aquatic animal health professionals or based on laboratory test results.

Avoid indiscriminate or prolonged antibiotic use, as it may contribute to antimicrobial resistance and compromise food safety.

Effective Prevention Measures

Preventing disease is more cost-effective than treating outbreaks.

Use Healthy Fingerlings

Purchase fingerlings from reputable hatcheries.

Healthy fingerlings should be:

Disease-free
Uniform in size
Free from deformities
Active and healthy

Proper Pond Preparation

Before each production cycle:

Remove bottom sludge
Dry the pond
Disinfect according to recommended procedures
Inspect the incoming water source

Proper pond preparation significantly reduces the presence of disease-causing pathogens.

Water Quality Management

Regularly:

Monitor water quality
Apply suitable probiotics
Prevent organic waste accumulation
Maintain a stable pond environment

Proper Feeding Practices

Avoid:

Overfeeding
Low-quality feed
Leaving uneaten feed in the pond

Feed should be adjusted according to the growth stage of the fish.

Daily Health Monitoring

Observe fish daily for:

Surface swimming
Loss of appetite
Abnormal swimming behavior
Increased mortality

Early intervention helps prevent disease spread.

Common Mistakes in Disease Management

Many farmers still make mistakes such as:

Relying solely on medication without improving water quality
Mixing multiple antibiotics indiscriminately
Ignoring water quality before treatment
Continuing heavy feeding during outbreaks
Failing to remove dead fish promptly
Neglecting to disinfect farming equipment between ponds

These practices can prolong disease outbreaks, increase treatment costs, and reduce overall effectiveness.

Purulent hepatorenal disease is one of the most serious diseases affecting pangasius farming and can cause substantial economic losses if not detected and managed promptly.

Understanding its causes, recognizing early symptoms, and implementing effective preventive measures can significantly reduce disease risks, improve survival rates, and enhance farm productivity.

In addition to maintaining good water quality, farmers should prioritize healthy fingerlings, balanced nutrition, and routine health monitoring. Whenever disease is suspected, consultation with aquatic animal health specialists or diagnostic laboratories is strongly recommended for accurate diagnosis and appropriate treatment.

An integrated management approach is the key to controlling purulent hepatorenal disease effectively while supporting sustainable and responsible pangasius aquaculture.

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