Diseases of crustaceans

Signs of disease

Important: animals with disease may show one or more of the signs below, but disease may still be present in the absence of any signs.

Clinical signs of disease in an infected animal

• lethargy
• emaciation
• soft shells
• heavy fouling from external parasites
• black gills
• reduced growth

Gross signs of disease in an infected animal

• digestive gland (hepatopancreas) degenerated - appears pale to white

Disease agent

Necrotising hepatopancreatitis is caused by a species of alpha-proteobacterium that infects the hepatopancreas of prawns, also referred to as NHP bacteria.

Host range

* naturally susceptible

Presence in Asia–Pacific

Necrotising hepatopancreatitis has been officially reported from Vietnam.

Epidemiology

• Necrotising hepatopancreatitis requires lengthy periods of high air temperature (29°–31°C) and elevated salinity (20–40 ppt).
• Mortality can be 90–95% within 30 days of an outbreak.
• Mortalities usually occur midway through the grow-out phase.
• Necrotising hepatopancreatitis appears to be transmitted by direct ingestion of an unidentified carrier (a reservoir host).
• The disease is not transmitted either vertically (from parent to offspring) or through cannibalism.