What is it?
IHHN suppresses the prawns immune system, allowing infection by other disease agents.
IHHN infection can result in cumulative mortalities as high as 90 percent in postlarvae
and juveniles, but mortality events seldom occur in infected adult prawns.
Where and when might it occur?
With a worldwide distribution, transmission of IHHN virus can be via horizontal or vertical routes. Horizontal transmission has been demonstrated by cannibalism or through contaminated water and vertical transmission has been demonstrated via infected eggs.
IHHN virus-resistant prawns and early life stages are carriers, and may transfer the virus to more susceptible species and life stages.
Gross signs of disease in an infected animal become evident from about 35 days of postlarval development. Infected shrimp often show reduced food consumption, cannibalism and repeatedly floating slowly to the water surface, rolling over and then sinking to the bottom.
The disease is also evident by high morbidity or mortality.
Other signs of the disease include poor hatching success of eggs and poor survival of larvae and postlarvae.
Gross pathological signs are:
- opaque abdominal musculature
In Pacific blue shrimp, additional gross pathological signs are:
- cuticular roughness
- cuticular deformities
- white to buff mottling of the shell, especially at the junction of abdominal shell plates
In Pacific blue shrimp, Pacific white shrimp and black tiger prawns, additional gross pathological signs are:
- blue appearance of moribund prawns
- runt-deformity syndrome, the effects of which include
- reduced and irregular growth in juveniles and subadults
- deformed rostrums growing to one side
Control and treatment
No effective vaccination methods for IHHNV have been developed.
Source: Australian Government, Department of Agriculture, Fisheries and Forestry