Acute Hepatopancreatic Necrosis Disease (AHPND / EMS)
AHPND (formerly EMS) is an early-stage shrimp disease caused by toxin-producing Vibrio parahaemolyticus. Mortality reaches 100% within 30–35 days of stocking, before harvest is possible.
Clinical signs
- Mortality between 10–35 DOC (the defining timing signal)
- Empty gut and empty stomach in moribund shrimp
- Pale, atrophied hepatopancreas — often shrunk to half normal size
- Soft shells, lethargy, slow swimming at the surface
- Cumulative mortality 40–100% within 7–14 days of onset
Transmission
- Oral: the PirAB toxin is delivered when shrimp ingest the bacterium
- Waterborne: V. parahaemolyticus is ubiquitous in brackish water; the toxin-plasmid strain is what causes disease
- Bottom sediment is the main reservoir — sediment temperature and organic load drive bacterial bloom
- Stress triggers: salinity drops, ammonia spikes, low DO all precede outbreaks
Diagnosis
- PCR for the pirA / pirB toxin genes (definitive)
- Field: early mortality (10–35 DOC) + empty gut + pale HP = strong AHPND suspicion
- Histopathology: massive sloughing of hepatopancreatic tubule epithelial cells
- Bacterial culture on TCBS agar — green colonies suggest V. parahaemolyticus, then PCR-confirm toxin genes
Treatment & emergency response
- No registered antibiotic protocol — irresponsible antibiotic use breeds resistance and triggers export rejections
- Reduce feed by 50% to lower organic load and bacterial bloom pressure
- Raise salinity by 2–3 ppt if feasible (vannamei tolerates AHPND less well at low salinity)
- Maintain DO above 5 mg/L through 24/7 aeration
- If cumulative mortality exceeds 30% before 30 DOC: emergency harvest is rarely viable; drain, disinfect, and restart
Prevention
- PCR-screen PLs and broodstock for AHPND-causing strains
- Pond preparation: full dry-out + 1,000 kg/ha CaO + 14-day sun-drying minimum
- Probiotic application from day 1 — Bacillus subtilis and B. licheniformis at 10⁶ CFU/mL of pond water, weekly
- Avoid stocking densities above 100 PL/m² where AHPND is regionally prevalent
- Stable salinity (15–25 ppt for vannamei) — sudden drops trigger outbreaks
- Reduce feed by 30% during the first 25 DOC to limit hepatopancreas stress
- Monitor TCBS Vibrio counts weekly — sucrose-negative (green) colonies above 10³ CFU/mL is a warning signal
Biosecurity checklist
- Source PLs only from AHPND-PCR-negative batches
- Apply Bacillus probiotics every 5–7 days for the first 35 DOC
- Weekly TCBS plating of pond water — log green colony counts
- Never re-use water from an AHPND-positive pond without 24h chlorination
- Reject any feed bag with moldy or musty smell — Aspergillus + Vibrio is a documented co-trigger
Regional prevalence
See where AHPND is being reported right now across India and Southeast Asia, with weekly trend lines and per-district drilldowns.
Open the heatmap →Frequently asked questions
What is AHPND in shrimp farming?
AHPND (Acute Hepatopancreatic Necrosis Disease), originally called EMS (Early Mortality Syndrome), is a bacterial shrimp disease caused by Vibrio parahaemolyticus strains carrying the pirA / pirB toxin plasmid. The toxin destroys hepatopancreas cells, causing mass mortality within the first 35 days of stocking.
What causes EMS in shrimp?
EMS is caused by a specific subset of V. parahaemolyticus carrying the binary PirAB toxin on a plasmid. Plain V. parahaemolyticus is harmless and ubiquitous — it's only the toxin-plasmid strains that cause disease. PCR for the pirA/pirB genes distinguishes the two.
How do you prevent AHPND in shrimp ponds?
Three levers: source PCR-negative PLs, run a strict probiotic program (Bacillus subtilis + B. licheniformis from day 1), and control pond bacterial load through reduced feeding during the first 25 DOC plus weekly TCBS Vibrio counts. Stable salinity and DO above 5 mg/L close the gap.
Can antibiotics treat AHPND?
No registered antibiotic protocol works reliably, and antibiotic use is heavily restricted by EU, US and Japanese importers. Antibiotic residues cause export rejections that can cost a farm more than the disease itself. Probiotics and management — not antibiotics — are the answer.
How is AHPND different from WSSV?
Timing and cause. AHPND is bacterial (V. parahaemolyticus) and strikes in the first 35 days of stocking. WSSV is viral and can strike at any stage. AHPND shows empty guts and pale hepatopancreas; WSSV shows white spots on the inner carapace and reddish bodies. Both can cause 100% mortality but require completely different management responses.
Catch AHPND before it costs a cycle
CAMARON's Disease Vision module flags AHPND from a single farm photo, ties findings to the regional heatmap, and walks you through the protocol.