BGD
Bacterial
🟡 Moderate
✓ Treatable
Bacterial Gill Disease
🦠 Flavobacterium branchiophilum · Flavobacteriaceae
📋 Overview
BGD commonly affects juvenile salmonids under conditions of high stocking density, poor water quality, and low oxygen. The bacterium colonises gill surfaces causing hyperplasia and mucus overproduction. Though rarely the primary cause, it exacerbates other gill-damaging conditions.
📊 Key Facts
Causative Agent
Flavobacterium branchiophilum
Agent Family
Flavobacteriaceae
Geographic Range
Worldwide in freshwater salmonid farms
Transmission Routes
Water-borne, crowding stress
Primary Host
Salmonids, particularly juvenile rainbow trout and salmon
Vaccine
✗ None / Experimental
🩺 Clinical Signs
Increased respiratory rate, fish congregating at surface, milky gill coloration, gill clubbing and lamellar fusion, mucus excess.
🔬 Symptoms
🔬
Rapid opercular movement
Respiratory Acute
🔬
Milky gill coloration
Respiratory Subacute
🔬
Lamellar fusion and clubbing
Respiratory Chronic
🔬
Surface piping
Respiratory Acute
🧪 Diagnosis
Wet mount of fresh gills (filamentous bacteria), culture, PCR.
💊 Treatment
Potassium permanganate bath, chloramine-T, formalin, improve water quality.
🛡️ Prevention
ℹ️ Prevention is the most effective strategy for managing this disease in aquaculture and aquarium settings.
Reduce stocking density, optimise water quality and oxygen, minimise stress.