Disease & Pathologycritical Threat Level

White Spot Syndrome (WSSV) — Comprehensive Pathology & Treatment Protocol

Dr. K. S. Murthy(ICAR-CIBA Senior Aquatic Pathologist)
6 min read
Verified ICAR-CIBA Protocol

Critical Bio-Hazard Advisory

This pathogen causes rapid mortality up to 100% within 3 to 10 days. Take immediate biosecurity precautions and notify neighboring aquaculture farms in your canal cluster.

1. Clinical Overview & Background

White Spot Syndrome (WSSV) is caused by White Spot Syndrome Virus (WSSV). It represents a CRITICAL-risk threat to commercial shrimp and fish farming operations across India.

Outbreaks are frequently triggered by sudden environmental stress, such as heavy rainfall, water temperature fluctuations exceeding 3°C within 24 hours, or sudden drops in dissolved oxygen below 3.5 mg/L.

Early diagnosis and strict biosecurity protocols are critical to halting transmission across adjacent ponds in the cluster.

2. Symptoms & Field Diagnostic Signs

Inspect pond stock daily using checktrays and cast nets. Look for these primary clinical indicators:

White spots (0.5–2 mm) on cuticle and exoskeleton
Reddish-pink discolouration of the body
Sudden mass mortality (up to 100% in 3–10 days)
Shrimp crowd at pond edges; reduced feeding
Loose shell, soft body texture

3. Pathogen Agent & Vector Characteristics

Causative Agent: White Spot Syndrome Virus (WSSV)

Primary vectors include wild crabs, aquatic birds, un-sterilized cast nets, contaminated intake water, and infected post-larvae (PL) batches from non-SPF hatcheries.

4. Step-by-Step Action Protocol

01

Immediately isolate affected ponds and stop water exchange with neighboring culture ponds.

02

Reduce daily feed rations by 50% to prevent organic loading and toxic ammonia accumulation.

03

Increase continuous aeration to maintain Dissolved Oxygen (DO) strictly above 5.0 mg/L.

04

Apply recommended disinfectant or therapeutic probiotic dosage as prescribed by an aquatic health specialist.

05

If mass mortality exceeds 20% in 48 hours, conduct emergency harvest of viable stock to recover costs.

Specific Treatment Note: No approved cure. Immediate harvest of survivors is recommended. Disinfect pond with 30 ppm bleach before restocking.

5. Water Parameters & Dosage Benchmarks

Parameter / ItemRecommended ValueOperational Importance
Target Salinity Range15 – 25 pptOsmo-regulatory stress reduction
Critical DO Threshold> 5.0 mg/LPrevents stress-induced immune suppression
Water pH Stability7.5 – 8.3Controls toxic un-ionized ammonia spikes
Disinfectant Dosage (Emergency)20–30 ppm Active ChlorineComplete pond water sterilization post-harvest

6. Long-Term Biosecurity & Preventive Measures

  • Source SPF (specific pathogen free) post-larvae only
  • Install 200-micron mesh screens on pond inlets
  • Strict biosecurity — disinfect equipment with 30 ppm chlorine
  • Avoid introduction of wild crustaceans into pond
  • Monitor water parameters daily; stress weakens immunity

7. Frequently Asked Questions

Q: Can White Spot Syndrome spread to neighboring ponds through birds or equipment?

Yes. Aquatic birds, cast nets, boots, and unsterilized aeration equipment act as mechanical vectors carrying the pathogen between ponds.

Q: Is it safe to consume shrimp harvested during an outbreak?

Yes, shrimp pathogens like WSSV and AHPND are specific to crustaceans and pose zero health risk to humans.

Q: How long should a pond remain dry before restocking after an infection?

Ponds should undergo sun-drying for 10–14 days until soil cracks, followed by quicklime treatment at 200–300 kg/acre.

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