VNN/VER
Viral
🔴 Fatal
💉 Vaccine Available
Viral Nervous Necrosis
🦠 Betanodavirus (nervous necrosis virus, NNV) · Nodaviridae
📋 Overview
VNN/VER is the most economically important viral disease of marine aquaculture globally. It infects neural and retinal tissue, causing vacuolation and necrosis. Larvae and juveniles are most severely affected with near-total mortality. Surviving fish may remain neurologically impaired.
📊 Key Facts
Causative Agent
Betanodavirus (nervous necrosis virus, NNV)
Genome Type
ssRNA, bipartite
Serotypes
RGNNV, SJNNV, BFNNV, TPNNV
Geographic Range
Worldwide in marine fish aquaculture
Transmission Routes
Vertical (broodstock to eggs), horizontal, water-borne
Primary Host
>120 marine fish species; European sea bass, grouper, halibut, turbot
🩺 Clinical Signs
Spiral or looping swimming, whirling, floating at surface, loss of schooling behaviour, loss of pigmentation, blindness.
🔬 Symptoms
🔬
Spiral/looping swimming
Neurological Acute
🔬
Loss of pigmentation
Integumentary Subacute
🔬
Floating at surface
Neurological Acute
🔬
Blindness
Ophthalmic Chronic
🧪 Diagnosis
RT-PCR, cell culture (E-11), ELISA, histopathology (vacuolation in brain/retina).
💊 Treatment
⚠️ No universally approved treatment is currently available. The information below covers supportive care and experimental approaches.
No treatment. Supportive — reduce stocking density.
🛡️ Prevention
ℹ️ Prevention is the most effective strategy for managing this disease in aquaculture and aquarium settings.
PCR screening of broodstock, ozone or UV treatment of water, vaccine (available in some countries for sea bass).