Sardine viral hemorrhagic septicemia
Viral hemorrhagic septicemia (VHS) is a serious viral disease that affects many fish species, including sardines (Sardina pilchardus). It is caused by a rhabdovirus which attacks several internal organs and causes bleeding. This disease is...
What is it?
Viral hemorrhagic septicemia (VHS) is a serious viral disease that affects many fish species, including sardines (Sardina pilchardus). It is caused by a rhabdovirus which attacks several internal organs and causes bleeding. This disease is closely monitored by health authorities because it can cause significant losses in fish populations, whether wild or farmed. It is among the notifiable diseases in many countries.
Key point
Disease with increased health surveillance due to its high mortality potential and its contagiousness.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Affected fish swim abnormally, sometimes spinning around or staying near the surface without reacting. \nWe often observe a swelling of the belly, pale gills and sometimes cloudy or bulging eyes. \nSmall hemorrhages (red dots or areas) may appear on the skin, at the base of the fins or in the eyes. \nFish become lethargic, stop feeding and sometimes congregate on the surface or near banks. \nIn acute forms, mortality can occur quickly without all these signs being visible.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The disease is caused by a rhabdovirus, an RNA virus that infects cells in several organs (kidney, spleen, heart, nervous system). \nThis virus multiplies particularly well in cold to temperate waters, which influences the seasonality of the disease.
Cold water favors the clinical expression of the disease. \nStress linked to high population density, poor water quality or sudden temperature variations increases the sensitivity of fish. \nMovements of fish between areas or ponds without health controls encourage the spread of the virus.
Transmission
The virus is mainly transmitted by direct contact between fish or through contaminated water, particularly via the excretions and secretions of infected animals. \nThe movement of fish between geographic areas or installations can promote its spread.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The diagnosis is based on specialized laboratory analyses, in particular the search for the virus by molecular biology techniques or by viral culture from samples of internal organs. \nA veterinarian or fish pathology specialist should be involved as soon as abnormal mortality is suspected, as this disease is subject to official surveillance in some countries.
Treatment
There is no specific antiviral treatment validated for this disease in fish. \nThe treatment aims above all to limit stress, improve environmental conditions and isolate affected populations to avoid the spread. \nHealth authorities may impose movement restriction or stamping out measures according to the regulations in force.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
There is no vaccine available in routine use for this disease in sardines. \nPrevention is mainly based on the health surveillance of populations, the control of fish movements and the avoidance of the introduction of animals whose health status is unknown. \nMaintaining good water quality and limiting stress factors helps reduce the risk of clinical onset.
Possible complications
The disease can cause massive and rapid mortality in affected populations, particularly in young individuals or in cases of significant environmental stress. \nSerious internal damage (kidney, spleen, heart) compromises the long-term survival of fish that survive the acute phase.
When to see a veterinarian
Observation of unusual or sudden mortalities in a sardine population.
Fish exhibiting abnormal swimming, lethargy or abdominal swelling.
Presence of visible bleeding on the skin, eyes or at the base of the fins.
Suspicion of contagious disease in a breeding or captivity context.
Prognosis
The prognosis is poor in cases of acute infection, with a high risk of mortality, particularly in young fish or during stressful conditions. \nFish that survive may remain carriers of the virus and represent a source of contamination for other populations.
Frequently asked questions
Does viral hemorrhagic septicemia only affect sardines?
No, this virus can infect many species of fish, marine and freshwater, depending on the viral strains in circulation.
Can we treat a fish with this disease?
There is no specific antiviral treatment. Treatment aims to limit stress and prevent it from spreading to other fish.
Is this disease dangerous for humans?
No, it is not transmissible to humans. It only affects fish.
How can we prevent this disease from appearing on a farm?
By controlling fish movements, monitoring water quality and limiting stress factors for animals.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
Content reviewed by the TunisieVet editorial team · Updated 18 August 2026
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