ECONOMIC AND ECOLOGICAL IMPACT OF WHITE GUT DISEASE

Why In News?

The Andhra Pradesh State Agriculture and Fisheries Ministry launched surprise inspections of hatcheries and laboratories in West Godavari district following detections of White Gut Disease (WGD). 

What is White Gut Disease?

White Gut Disease (WGD), also known as White Feces Syndrome (WFS) or White Feces Disease (WFD), is a severe gastrointestinal disorder affecting farmed shrimp, primarily the Pacific white shrimp (Litopenaeus vannamei).

Target Organisms: Pacific white shrimp (Litopenaeus vannamei) and Black tiger shrimp (Penaeus monodon).

Primary Vectors: A combination of Vibrio bacteria species (e.g., Vibrio parahaemolyticus) and the microsporidian parasite Enterocytozoon hepatopenaei (EHP).

Type of Disease: Multifactorial syndrome (not caused by a single pathogen alone, but triggered by an interplay of infectious agents and environmental stress).

Major Indian Hotspot: Coastal aquaculture farms, notably in Andhra Pradesh (India's leading fish and shrimp producer) and the eastern coast.

Etiology and Causes

The disease manifests due to a combination of biological, environmental, and management hazards: 

• Pathogenic Synergy: It involves co-infection by Gram-negative Vibrio bacteria strains alongside Enterocytozoon hepatopenaei (EHP), an intracellular microsporidian parasite that replicates inside the shrimp's digestive gland (hepatopancreas).  
• Environmental Stressors: High stocking density in intensive farming, elevated water temperatures (exceeding 32°C), and sudden algal blooms or plankton crashes.  
• Poor Water Quality: Accumulation of toxic gasses like ammonia, nitrites, and hydrogen sulphide due to improper bottom management of the ponds.  
• Dietary Toxins: Anti-nutritional factors or mycotoxins present in sub-standard feed.  

Pathophysiology and Symptoms

• White Fecal Strings: The hallmark sign of the disease is the presence of white, buoyant, thread-like fecal strings floating on the pond surface.  
• Tissue Deterioration: The white mass is not just waste, but a collection of peeled-off microvilli and decaying digestive tissues from the shrimp's hepatopancreas and midgut.  
• Physical Manifestation: The shrimp exhibit an empty or pale/milky digestive tract, a softened or loose exoskeleton, and dark gills.  
• Behavioral Changes: Severe reduction in feed consumption (anorexia), growth stagnation, and lethargy.  

Socio-Economic Impact

• Yield Loss: WGD weakens the shrimp over time and leads to chronic mortalities, reducing total pond output by up to 60%.
• Impact on Trade: India is one of the world's largest exporters of seafood, particularly frozen shrimp to markets like the US and EU. Large-scale outbreaks threaten rural livelihoods, coastal economies, and national export reliability. 

Currently, there is no specific curative drug or novel treatment to reverse an advanced infection, making prevention paramount:  

Source: THEHINDU