Viral Hemorrhagic Septicemia in Farmed Fish

Viral hemorrhagic septicemia is a devastating fish disease affecting multiple farmed and wild species, causing mass mortality events with significant welfare and economic impacts.

Key Facts

VHS is caused by a rhabdovirus affecting over 50 fish species
It causes hemorrhaging, neurological symptoms, and rapid death
Mass mortality events in wild populations have occurred in the Great Lakes
Rainbow trout are highly susceptible in aquaculture settings
The virus spreads through water and infected fish
No effective treatment exists - prevention through biosecurity is critical
Infected fish show erratic swimming, darkening, and hemorrhagic lesions
VHS is a notifiable disease in many countries requiring mandatory reporting

Welfare Considerations

Fish infected with VHS suffer from hemorrhaging and neurological damage causing disoriented, erratic behavior before death. The disease spreads rapidly through contained aquaculture systems, potentially causing suffering to thousands of fish in a single outbreak. Because treatment options are minimal, outbreaks often result in mass culling of entire populations. The suffering associated with both the disease and emergency culling represents a significant welfare burden in affected operations.

What You Can Do

Support strict biosecurity protocols in aquaculture operations
Advocate for mandatory disease surveillance in commercial fish farming
Never release bait fish or aquarium fish into wild waterways
Support research into VHS vaccines and antiviral treatments
Learn about responsible fish purchasing from disease-free certified farms