Mycobacteriosis - fish tuberculosis disease

Mycobacteriosis - fish tuberculosis disease

1. General description

Fish tuberculosis is chronic bacterial disease. The bacillus responsible for this disease are resistant to many environmental factors as temperature or pH fluctuations (they are resistant to low and high values). The bacteria divide slowly so development of the disease isn't rapid. Their endospores can survive 3 months or longer.

Fish usually infect by digestive system (infected food, contact with dead infected fish, infected organic matter in aquarium), gills and skin (damaged injuries or other diseases). Infected female can infect her young.

Fish tuberculosis is one of the most deadly and dangerous disease because visible symptoms appear when it is advanced. This disease is practically asymptomatic in the initial phase. Infection progresses with time. Then the internal organs are attacked, there are gray-whitish granulomas on these organs which cause their swelling. The skeletal system are also attacked – spine of the fish deforms.

Attempts to treat sick fish are practically ineffective but we need remember that fish without visible symptoms are also threat. These potentially healthy fish may be vectors of bacillus and they can be source of infection or they can become sick after some time (bacillus often reside in the host organism in a dormant phase).

2. Type of the disease

This is bacterial disease.

3. Cause of the disease

Causes of this disease are bacillus from Mycobacterium genus.

4. Favorable circumstances for development of the disease

• wrong water parameters – too low pH, bad water temperature (usually too high), oxygen-poor water, too much organic matter in aquarium,
• monotony diet,
• too much fish in aquarium,
• improper lighting,
• injuries skin or gills,
• infected snails,
• infected live food.

5. Common symptoms of the disease

• loss of body colours,
• frayed fins,
• protruding scales,
• dropsy around the bell – bacteria probably develop in the digestive system, liver and kidneys,
• damage and loss of scales,
• whitish nodules in the internal organs, on the skin and fins which crack and create sores (visible congestion and wounds),
• protruding/pop eyes,
• fish hangs in the water and its tail vibrates,
• deformed the spine,
• scrawny the body,
• loss of appetite,
• apathy.

6. Types of the treatment

This disease is difficult to cure. Its symptoms are advanced, organs are exhausted when we can diagnose it. Further mycobacteria are antibiotic resistant in most cases.

We may try to treat sick fish but we have very small chance to succeed. We must remove all sick fish from aquarium when treatment isn't effective. We should commit an act of euthanasia these fish and we must disinfect the tank.

All sick fish we transfer to a separate aquarium at the time of treatment. We must use gloves when we have contact with ill fish.

6.1. Long-term bath with antibiotic

KANAMCIN and VITAMIN B6: we dose 10mg antibiotic per 100mg food and we feed sick fish for 10 days or we dose 10mg antibiotic per every litre of water, we dose 1 drop of vitamin per every 20 litres at the same time. The bath should last 30 days.

6.2. Disinfection of aquarium

We must use gloves before any actions. We use their always when we touch infected equipment, tank, water and fish.

The mycobacteria are resistant to bleach disinfection, other agents containing chlorine or ammonium compounds. They are sensitive to 60-85% alcohol.

All staff (especially filter media), substrate, decorative elements, aquarium we disinfect by spraying alcohol and we leave to dry. Next we must carefully wash all. We may use to disinfection isopropyl alcohol or antiseptic with an alcohol content of minimum 60%.

We must carefully wash our hands in 70% isopropyl alcohol or antiseptic and antibacterial soap after the above actions.

7. Comments about this disease

• There is a risk of contracting the disease by humans. Symptoms of disease (pustules which look like a rash) may appear on the part of the body (e.g. hands, fingers, shoulders) which had direct contact with infected water.
• Described symptoms may suit other diseases e.g. fish dropsy disease or ichthyosporidium disease.
• Sick fish often suffer secondary bacterial infections.
• Species from warmer waters from Characidae, Cyprinidae, Belontiinae, Poecilidae, Cichlidae families and livebearer are the most susceptible on this disease.

8. Prevention

• we avoid rapid changes in water parameters – especially water temperature and pH,
• we systematic check water quality – we control level of ammonia and nitrites, chlorine, chloroamines and oxygen in water,
• we may use UV light for water sterilization,
• we use adequate diet – it should be varied, enriched in vitamins and microelements,
• we never overfeed fish – we feed fish only this amount of food which they may eat by a few minutes,
• we never keep too much fish in single aquarium,
• we should reduce stressful situations – we shouldn't do rapid partial water changes, we should only keep together fish with similar temperament, we shouldn't use chemicals if it isn't necessary, shoal fish we should keep in large groups, shy fish need hideouts among plants and etc.,
• we always quarantine new fish.