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Diseases of finfish

Viral diseases—Infectious haematopoietic necrosis

CLICK ON IMAGE TO ENLARGE infectious haematopoietic necrosis

Chinook salmon fry with infectious haematopoietic necrosis. Note characteristic darkening from the tail region, swollen stomach and haemorrhaging at base of fins

Source: J Fryer

CLICK ON IMAGE TO ENLARGE infectious haematopoietic necrosis

Rainbow trout fry with (left) and without (right) infectious haematopoietic necrosis. Note the darker colour of the infected fish

Source: G Kurath

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.

The disease signs described below are seen only in young salmonids (disease in adults is subclinical).

Disease signs at the farm level
Disease signs at the tank or pond level
Clinical signs of disease in an infected animal
Gross signs of disease in an infected animal

Disease agent

Infectious haematopoietic necrosis is caused by infectious haematopoietic necrosis virus (IHNV), a rhabdovirus related to viral haemorrhagic septicaemia virus.

Host range

Fish known to be susceptible to infectious haematopoietic necrosis virus:
amago salmon* (Oncorhynchus rhodurus)
Atlantic salmon* (Salmo salar)
brook trout* (Salvelinus fontinalis)
brown trout* (Salmo trutta)
chinook salmon* (Oncorhynchus tshawytscha)
chum salmon* (Oncorhynchus keta)
coho salmon* (Oncorhynchus kisutch)
cutthroat trout* (Salmo clarki)
masou salmon* (Oncorhynchus masou)
Pacific salmon* (Oncorhynchus spp)
pink salmon* (Oncorhynchus gorbuscha)
rainbow trout* (Oncorhynchus mykiss)
sockeye salmon* (Oncorhynchus nerka)
Arctic char (Salvelinus alpinus)
gilt-head seabream (Sparus aurata)
Pacific herring (Clupea pallasii)
pike (Esox lucius)
pile perch (Damalichthys vacca)
shiner perch (Cymatogaster aggregata)
tubesnout stickleback (Aulorhynchus flavidus)
turbot (Scophthalmus maximus)
Nonpiscine carriers include:
gill lice (Salminicola spp)
leeches (Piscicola spp)
mayfly (Callibaetis sp)

* naturally susceptible (other species have been shown to be experimentally susceptible)

Presence in Asia–Pacific

Map showing  presence in Asia–Pacific

IHN has been officially reported from China, Iran, Japan and the Republic of Korea.


Differential diagnosis

The differential diagnostic table and the list of similar diseases appearing at the bottom of each disease page refer only to the diseases covered by this field guide. Gross signs observed might well be representative of a wider range of diseases not included here. Therefore, these diagnostic aids should not be read as a guide to a definitive diagnosis, but rather as a tool to help identify the listed diseases that most closely account for the gross signs.

Similar diseases

Viral haemorrhagic septicaemia, infectious salmon anaemia, infectious pancreatic necrosis

Sample collection

Because of uncertainty in differentiating diseases using only gross signs, and because some aquatic animal disease agents might pose a risk to humans, you should not try to collect samples unless you have been trained. Instead, you should phone your national hotline number and report your observations. If samples have to be collected, the agency taking the call will advise you on what you need to do. Local or district fisheries/veterinary authorities could advise you on sampling.

Emergency disease hotline

For your national emergency disease hotline number, see Whom to contact if you suspect a disease.

Further reading


The currently accepted procedures for a conclusive diagnosis of IHN are summarised at

These hyperlinks were correct and functioning at the time of publication. infectious haematopoietic necrosis infectious haematopoietic necrosis

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