Marine Vibriosis: symptoms, treatment, prevention

Vibrio anguillarum and related Vibrio species are major Gram-negative pathogens of marine fish causing hemorrhagic septicemia and ulcerative skin lesions.

Overview

Marine Vibriosis is caused by Vibrio anguillarum and related Vibrio species (notably V. harveyi). It is a leading cause of hemorrhagic septicemia and ulcerative disease in marine aquaria, with very high mortality, especially in newly imported or stressed reef fish.

Symptoms

Red ulcers and hemorrhages
Skin and fin necrosis
Popeye
Darkening of body color
Anorexia
Rapid death

Causes

Transport stress, unstable salinity or temperature, overcrowding and poor diet allow Vibrio to overwhelm fish defences. The bacteria are ubiquitous in seawater and become pathogenic when fish are compromised.

Diagnosis

Rapidly progressing red ulcers, fin necrosis and popeye in a marine fish, especially shortly after import, suggest Vibriosis. Bacterial culture and identification by a fish veterinarian are required for confirmation; distinguish from marine Aeromonas-like infections.

Treatment

Move affected fish to quarantine and start medicated feeding; lowering temperature within species tolerance reduces Vibrio virulence.

Quarantine

A bare-bottom hospital tank with stable salinity, strong aeration and mature filtration is essential. Do not medicate the display tank because antibiotics destroy the biofilter and can harm invertebrates.

Medication

Florfenicol at 10 mg/kg fish in medicated food daily for 10 days in quarantine.
Oxytetracycline as an alternative in food or water in quarantine; lower temperature to about 24 °C if the species tolerates.

Recovery

Provide enriched feeding and minimise handling stress during recovery. Hold fish in quarantine for the full course before returning them to the display.

Prevention

6-week marine quarantine for all new arrivals
Stable salinity and temperature
Minimise transport stress
Avoid stacking parasite treatments and stressors at once