symptoms
external symptoms
- eyes fall out.
- pop eyes.
- colors become pale.
- Fish lose weight.
- inflammation on the skin.
- Open and bloody spots on the body.
- Black or brown spots on the body that later burst open and lead to open, bloody areas.
- Fins recede.
- Scales fall out.
- Scales stand off.
- Fish lose weight.
- Belly becomes abnormally fat.
- crippling of the jaw.
- curvature of the spine.
Behave
- reluctance to eat
- Pisces become sluggish and apathetic.
- Fish swim jerkily.
- Fish slide on their stomachs.
- Fish separate.
- Fish stand in corners or on the bottom.
internal symptoms
- Whitish-gray nodules (cysts) form on internal organs.
- Nodules form in muscles. These result in the brown or black spots on the body listed above.
photos
Dwarf gourami with wounds on the body typical of fish tuberculosis. This case is probably due to Epizootoc ulcerative syndrome (EUS), which is spreading in Asia and also affects dwarf gouramis.
Photos: A. Marquardt
Female dwarf gourami with typical wounds on the body. Also in the second picture, in front of the dorsal fin and behind the eye.
Photos: Karin Kersting
Victoria cichlid with fish tuberculosis. The cichlid is very pale and has a very sunken belly.
Photos: J. Dazio
Gourami died within 10 days, presumably of fish tuberculosis. In such cases, EUS is suspected in gourami.
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causes
Fish tuberculosis is caused by bacteria of the genus Mycobacterium (mycobacteria). These bacteria are found in almost every aquarium, e.g. B. in the substrate, in the sludge, in uneaten food and on dead creatures. These bacteria are also often found on and in healthy fish. Depending on the study, up to 80% of all aquarium fish are infected by mycobacteria. The average value of the studies is 40 to 60%. For this reason, bacteria that cause tuberculosis are often found in dead fish and wrongly assumed to be the cause of death.
However, mycobacteria should not be underestimated either. In the literature, it is almost always assumed that fish tuberculosis is the most common bacterial disease in aquarium fish. The fact that many fish are infected by mycobacteria without becoming ill does not mean that the fish have become immune and that the mycobacteria are harmless. Healthy and strong fish are protected by their mucous membrane or by the mucus produced from bacteria being able to attach themselves to their skin surface. The bacteria mainly live in this mucus. As soon as the mucus layer is damaged, a breeding ground is created for the bacteria on which they can multiply explosively, even if the damage is only microscopic.
This is probably why fish tuberculosis often occurs when new fish are introduced into an aquarium with existing fish stocks. Tuberculosis can be introduced with the new fish, or pathogens present in the tank can find suitable reproduction opportunities as a result of disputes over hierarchy or other stress factors.
However, the immune system of healthy fish can usually fight off the mycobacteria. Only in the case of weakness, e.g. B. due to poor living conditions or due to a vitamin-poor diet, the fish tuberculosis breaks out. Fish tuberculosis is very contagious and can spread directly from fish to fish, or indirectly, e.g. B. on the ground, spread. The course of the disease can be very slow, so that a fish dies from time to time. However, the course can also be epidemic-like, so that entire stocks die within a short time. It has not yet been clarified whether the different course is caused by the respective husbandry conditions, or whether different dangerous strains of bacteria are responsible for it.
Infected fish that are cared for under optimal conditions can envelop the bacteria in the body with connective tissue and thus deactivate them. These so-called granulomas can be seen under a microscope at approx. 200x magnification. Granulomas often occur in the liver and kidneys. However, similar encapsulations also occur in other diseases. If too many granulomas develop, vital bodily functions can be disrupted. Under unfavorable conditions, the enveloping connective tissue can dissolve again. The bacteria then become active again.
Mycobacteria can survive for a long time in the substrate, sludge, on plants, decorative objects, etc. The fish tuberculosis can come back like this again and again break out againas soon as the living conditions of the fish deteriorate.
Due to the large number of different symptoms that can occur individually or together and are also symptoms of other diseases, fish tuberculosis can only be vet be diagnosed with certainty.
transmission to humans
People cannot become infected with pulmonary tuberculosis from fish tuberculosis. However, the mycobacteria of the species Mycobacterium marinum find suitable colonization conditions in skin folds and open wounds. Severe and unpleasantly itchy skin rashes and eczema can be the result. The first symptoms therefore appear on the hands or arms. For this reason, you should never reach into an aquarium with open wounds if the stock is suspected of having tuberculosis.
The disease in humans is called pool granuloma because it can be transmitted through water in aquariums and in swimming pools. The disease used to be relatively widespread. Because lakes and rivers are rarely used as bathing water, the disease has become rare. Within 2 to 4 weeks, inflammatory, blue-red nodules develop, which can be about 2 cm in size and are painful. Because the pathogen can spread via the lymphatic system, a number of these nodes can appear on the arm. In advanced stages, tendons and bones can be affected.
The disease is detected using typical changes in a tissue sample or by detecting the pathogen in a bacterial culture. The disease clears up within a few weeks with appropriate antibiotic treatment. Even if left untreated, healing often occurs after a few months. Individual affected areas can be surgically removed in severe cases.
Because the disease is rare today and therefore largely unknown, the nodules are often confused with abscesses. According to an older newspaper report from the “Welt”, 63 cases of illness occurred in France between 1996 and 1998.
You can prevent this by only reaching into the aquarium with gloves.
treatment suggestions
The best measure against fish tuberculosis is appropriate prevention by providing the fish with optimal living conditions. A varied diet, sufficient space and good water hygiene play a special role here. New arrivals must be observed in quarantine for at least two to three weeks.
Once diseased fish can usually not be cured. At best, the course of the disease can be delayed by treatment with antibacterial drugs.
Increases in temperature do not make sense because the pathogens also multiply well at 37°.
General recommendations beyond this are difficult because the course of the disease can be very different.
Due to the high risk of infection, diseased fish must be isolated immediately. If these are not isolated cases and no quarantine option is available, diseased animals should be killed. It is not necessary to kill the entire stock, including the healthy animals, even though this is often recommended.
In the case of a very severe infestation, in which new fish keep getting sick, it should be considered not to supplement the existing stock with new purchases, but to slowly let them die out naturally. Before restocking, infested aquariums and objects should be thoroughly disinfected. In this case, the plants should be destroyed.