Acute hepatopancreatic necrosis disease (AHPND) earlier known as early mortality syndrome (EMS) or acute hepatopancreatic necrosis syndrome (AHPNS) has been causing significant losses in shrimp farms in China, Vietnam, Malaysia, and Thailand since 2009. The disease affects both black tiger shrimp and Pacific white shrimp and is characterized by mass mortalities during the first 20-30 days of stocking.

Research by the University of Arizona has identified that the disease is caused by the bacterial agent Vibrio parahaemolyticus, which is transmitted orally and colonizes the shrimp’s gastrointestinal tract. This then produces a toxin that causes tissue destruction and dysfunction of the shrimp digestive organ known as the hepatopancreas.

Causes

The disease is caused by a unique strain of Vibrio parahaemolyticus, which can produce toxins responsible for the primary pathology in affected shrimp. Other non-Parahaemolyticus strains such as V. campbellii, V. harveyi, V. owensii, and V. punensis are also found to contain the same toxic genes and may also cause the disease.

Symptoms

• Erratic swimming or swimming near the bottom of the pond
• Reduced growth
• Pale, shrunken or atrophied hepatopancreas
• Whitening of the hepatopancreas
• Reduction in size of hepatopancreas
• Soft texture of the exoskeleton
• Dark spots or streaks on the hepatopancreas
• Hardening of hepatopancreas

Management

• There is no quick fix for EMS/AHPND – once a farm is infected a carefully balanced management plan is required.
• In a worst-case scenario, farmers should be prepared to harvest all ponds at short notice.
• There must implement strict biosecurity measures and a thorough disinfection phase to manage the disease and avoid future outbreaks.
• PL needs to be derived from AHPND-free broodstock. The general health of PL should be checked before stocking, including in stress tests.
• We can manage EMS/AHPND by preventing its further spread and providing better conditions to increase shrimp resistance to it.