EUS
Fungal
🔴 Fatal
🔔 OIE Notifiable
Aphanomyces Invadans (MAS Ulcerative Disease)
🦠 Aphanomyces invadans (syn. A. piscicida) · Saprolegniaceae (Oomycete)
📋 Overview
EUS causes massive epizootics following flooding and seasonal rains in Asia and Australia, affecting hundreds of wild and farmed fish species. The oomycete invades through skin lesions and penetrates deeply into muscle tissue, creating characteristic necro-inflammatory granulomata around hyphae. It is OIE-listed due to its wide host range and economic impact.
📊 Key Facts
Causative Agent
Aphanomyces invadans (syn. A. piscicida)
Agent Family
Saprolegniaceae (Oomycete)
Geographic Range
Asia, Australia, Africa, Japan — affects hundreds of wild and farmed species
Transmission Routes
Water-borne zoospores; outbreak triggered by rainfall and flooding
Primary Host
Snakehead, carp, catfish, mullet, many wild freshwater species
Vaccine
✗ None / Experimental
🩺 Clinical Signs
Large deep ulcers on flanks and dorsum, necrotic reddish-brown muscle exposure, haemorrhagic margins, internal hyphae penetration, emaciation.
🔬 Symptoms
🔬
Large haemorrhagic ulcers
Integumentary Acute
🔬
Deep muscle necrosis
Musculoskeletal Acute
🔬
Reddish-brown wound coloration
Integumentary Subacute
🔬
Emaciation
Systemic Chronic
🧪 Diagnosis
Histopathology (non-septate invasive hyphae), culture, PCR.
💊 Treatment
ℹ️ Treatment options are limited. Consult a qualified fish health professional.
Lime treatment of pond water (raise pH), salt, malachite green (banned in food fish), benzalkonium chloride.
🛡️ Prevention
ℹ️ Prevention is the most effective strategy for managing this disease in aquaculture and aquarium settings.
Avoid stressors during seasonal risk periods, lime ponds pre-season, dispose of dead fish.