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Marine Flexibacter (Tenacibaculosis): causes, symptoms and treatment

Marine Flexibacter (Tenacibaculosis) (Tenacibaculum maritimum) — etiology, symptoms, diagnosis, active-substance medication, recovery and prevention; mortality without treatment: very high.

Overview

Marine relative of Columnaris causing erosive skin and fin lesions, mouth necrosis, and tail rot in marine fish. Highly contagious, often fatal. Causative agent: Tenacibaculum maritimum. Transmission: water. Incubation: 1-7 days. Reported mortality without treatment: very high.

Symptoms

  • yellowish necrotic skin patches
  • mouth and fin erosion
  • tail rot
  • frayed fins
  • cottony patches
  • rapid progression

Causes

Outbreaks are typically triggered by chronic stress, poor water quality, temperature swings, overcrowding, or the introduction of unquarantined fish. The pathogen spreads via free-swimming or waterborne stages in shared water.

Diagnosis

Diagnosis is based on clinical signs (lesions, hemorrhages, behaviour) combined with bacterial culture and Gram-staining where available. Differentiate from co-infections with other Gram-negative pathogens; antibiotic sensitivity testing improves treatment success against Tenacibaculum maritimum.

Treatment

Effective treatment requires isolating affected fish in a quarantine tank, identifying the pathogen, administering the appropriate active substance at the correct dose and duration, and supporting recovery with stable water parameters and nutrition.

Step 1: Quarantine

Set up a bare-bottom quarantine tank with a mature sponge filter, heater, and aeration. Match temperature and pH to the display tank, and acclimate fish slowly. A bare bottom simplifies daily siphoning and prevents medication from being absorbed by substrate.

Step 2: Medication

  1. Freshwater dip + antibiotics. 5-min freshwater dip can dislodge bacteria, then transfer to QT with florfenicol or oxytetracycline 10-14 days. (duration: 10-14 days)

Step 3: Recovery

After medication, perform a 30-50% water change and run fresh activated carbon for 24-48 hours to remove residues. Continue feeding a high-quality, varied diet with vitamins and immunostimulants. Reintroduce fish to the display tank only after at least one week without recurrence of symptoms.

Prevention

  • minimize handling injuries
  • good water flow
  • quarantine new fish
  • stable salinity and temperature