Fish tuberculosis: A Quick Guide

Fish tuberculosis

Fish tuberculosis is caused by bacteria. Below is a quick overview of the fish disease.

Fish tuberculosis (Mycobacterium fortuitum)

What is fish tuberculosis?

The fish Tuberculosis is a bacterial infection that predominantly occurs in fish in aquariums.

It is widespread and causes great losses. The disease of wild fish is possible but rare.

The disease occurs in both freshwater and saltwater fish, with infections being most common in tetras and rare in catfish.

The pathogens are different types of mycobacteria, with Mycobacterium marinum, M. fortuitum and M. chelonae being particularly frequently involved.

These bacteria are widespread in the aquatic environment and their mere presence does not generally lead to disease. Other favorable circumstances are necessary for an infection. This can be stress caused by overstocking or insufficient cleanliness in the aquarium.

In general, the risk of infection is increased by unfavorable housing conditions. The disease is usually introduced into an aquarium by newcomers. The pathogens can also survive saprophytic in the mud or sludge of the aquarium.

Mycobacteria(Fish tuberculosis) underlying cause

Fish tuberculosis Symptoms

The manifestations of fish tuberculosis are very diverse and make a diagnosis in living fish difficult. In most cases, fish tuberculosis is chronically progressive.

Chronic course

The gradual loss of individual animals from the stock over a longer period of time is the rule. Tubercles surrounded by a connective tissue capsule are typical.

In younger tubercles, acid-fast rods are still easy to find, in older tubercles their number is significantly lower.

Acute course

This form is characterized by extensive, exudative foci of inflammation. If the infection flares up suddenly, for example due to unusual stress, a total loss is possible within one or two weeks.

Infested animals usually show a lack of appetite, become apathetic and lose weight. The skin becomes inflamed with ulceration and the fins recede. In addition, “bulging eyes” (exophthalmos), panophthalmitis (disease of the entire eye) up to loss of eyes, flaky defects, fading of color, crippling of the spine and jaws, ascites and changes in behavior can occur.

When an infected animal is dissected, whitish-gray granulomas are found in almost all organs, especially the spleen, kidneys and liver. In the acute course, the intestines are often stuck together as a result of peritonitis (peritonitis). The rod-shaped pathogens can be detected in large numbers intra- and extracellularly.

How to identify and avoid catching fish TB, Tuberculosis Mycobacterium marinum

Fish tuberculosis Diagnosis and therapy

The diagnosis is made by histological evidence of the tubercular granulomas. Since the pathogens can also be part of the normal intestinal flora, their presence without pathological tissue changes is insufficient evidence of a disease. Infections with Nocardia, Ichthyophonus and Aeromonas ssp. excluded, which can also be associated with granulomas.

Although there have been isolated reports of treatment success with antibiotics, fish tuberculosis is currently not considered to be medically treatable. The focus must therefore be on preventing an outbreak through the best possible housing conditions and quarantine over four weeks for newcomers.

In acute cases, control is therefore carried out by killing the population and removing the aquarium equipment.

Then disinfect the aquarium and the technical furnishings. In the case of chronic courses, the removal of sick animals and the optimization of the housing conditions can be sufficient.

Is fish tuberculosis dangerous to people?

The Mycobacterium marinum, which causes fish tuberculosis, can be transmitted to humans and other mammals through the smallest of skin injuries. These infections cause so-called swimming pool or aquarium granuloma in humans

This is a sometimes stubborn granuloma that is restricted to the skin. Therapy usually shows rapid success. If left untreated, spontaneous healing usually occurs after one to two years. Treatment should still be carried out to avoid the spread of germs. As a preventive measure, it is advisable to wear protective gloves when cleaning aquariums.


Parts of this article were taken from Wikipedia and are under the commons attribution license.

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