Fish tuberculosis

Fish tuberculosis is widespread among fresh and salt water aquarium fish. This infectious disease mainly infects guppies, characins and angelfish. Fish tuberculosis is a zoonosis and can be transmitted to humans and other mammals.

Definition Fish tuberculosis

Fish tuberculosis is a bacterial infectious disease with an acute or chronic course. The symptoms are varied and usually not very specific. For this reason, fish tuberculosis can often only be detected by dissection of the animal.

The fish take up too little food and become emaciated. At the same time the abdomen is distended by the accumulation of fluid in the abdominal cavity. The spine is curved upwards and the jaw atrophies. The eyes are inflamed and emerge from the cavities(googly eyes). Nodules form in the muscles, which are filled with bacterial material. Brown spots become visible on the skin. The scales appear frayed and the colour fades. The fins partially recede. In order to reduce the itching, the fish rub themselves against various objects in the aquarium. Sick fish withdraw, they stand in the aquarium corners or on the bottom. The swimming movements appear jerky.

Summary of the main symptoms of the disease

  • insufficient feed intake
  • Emaciation with distended stomach
  • protruding eyes
  • Scale defects and colour loss
  • Nodules and brown spots
  • Ulcers
  • Degeneration of fins
  • Behavioural changes


Fish tuberculosis is caused by mycobacteria. Responsible for the disease are:

  • Mycobacterium marinum
  • Mycobacterium fortuitum
  • Mycobacterium chelonae
]The outbreak of fish tuberculosis is favoured by overstocking and poor hygienic husbandry conditions. The bacteria are usually introduced via new fish and require a water temperature of 37 degrees Celsius to multiply.


1. Chronic course

Clear symptoms of the disease are not visible. Tuberculosis, bumps, which contain pathogens, are found on the skin. Over a longer period of time individual fish die again and again.

2. Acute course

The fish eat badly and lose weight. Typical symptoms are the distended stomach and the curved spine. In an acute course, the entire fish population dies within two weeks.


The disease is fatal in 98% of the fish. A treatment with antibiotics is hardly successful. That is why the emphasis in the fight against fish tuberculosis is on prevention. New stock should in principle be kept in a separate quarantine tank for four weeks to prevent the introduction of mycobacteria into the stock. Infected fish must be removed from the aquarium as soon as possible. If acute fish tuberculosis is present, the entire stock must be killed. The aquarium and equipment must be thoroughly disinfected. The aquarium should be empty for at least six weeks.

Preventive measures against fish tuberculosis

  • sufficiently large aquarium
  • good water quality
  • high quality feed to strengthen the immune system of the fish
  • Hygiene
  • Reduction of stress

Be the first to comment

Leave a Reply

Your email address will not be published.