Last update: November 3, 2022

Fish Tuberculosis: A TB As Deadly To Fish As To Humans

Fish Tuberculosis is a common name for fish that are infected with Mycobacterium spp.

This bacteria has a protective outer layer or coating that makes it impossible to treat once it’s inside your system.  

Some infections may not show any clinical signs, while others may display different types of signs. It’s a significant disease because it is zoonotic and can also be passed to humans through open wounds. 

So let’s take a closer look at Fish Tuberculosis and how it affects both fish and humans. 

What Is Fish Tuberculosis?

So as we mentioned earlier, this is a Mycobacterium infection in fish and can be passed on to humans via open wounds. There are several bacterial species within the micro bacterium genus.

These are also common environmental contaminants and don’t require a fish host. In fact, they can also infect birds, mammals, and reptiles as well.

Some species will cause a localized infection, while others cause a  full-body systemic disease. The disease is referred to as “fish Tuberculosis” since the Mycobacterium that causes it is the cause for this infection in humans as well. 


Fish Tuberculosis is also referred to as an acid-fast disease, granuloma disease, or piscine tuberculosis. All fish species should be considered acceptable. Some species are a lot more susceptible than others, like neon Tetras,  gouramis, discus, and labyrinth air breathers.

Some of the clinical signs for this chronic progressive disease may differ from one fish species to the next. It may take years to develop into a clinically apparent illness. However, some of the signs and symptoms to look out for include:

  • Lethargy
  • Fin and scale loss
  • Anorexia 
  • Emaciation 
  • Ulceration
  • Skin inflammation 
  • Edema 
  • nodules in muscles that may deform the fish 
  • Peritonitis 
  • Erratic swimming
  • Popeye
  • Mouth lesions
  • Reddened skin
  • White feces

Examinations will usually reveal white or grey nodules in the liver, heart, kidney, or spleen. Skeletal deformities may also be present. Diagnosis is normally based on clinical signs and the presence of acid-fast bacteria in tissue sections. 

Infections can also be quite high in contaminated freshwater tropical fish production facilities. The aquatic environment is considered the reservoir.

Mycobacterium has been cultured from swimming pools, natural streams, beaches, tropical fish tanks, estuaries, and city tap water. 

How do Fish Get TB?

Causes of Fish Tuberculosis include :

  • Addition of non-symptomatic carrier fish
  • Addition of infected plants and other biological materials 
  • Transfer from the owner’s hands due to incorrect or improper sanitization. 

Usually, fish get infected by eating other dead fish who have been infected. They can also get infected from eating infected organisms.

With regard to humans, they usually get infected by large amounts of mycobacteria gaining access to the body through an open wound. So while both fish and humans can be infected in more than one way, humans are not likely to die from the condition. 

How to Treat Fish TB

Perhaps the only effective treatment for fish who have the infection to supportive care. While some fish manage to live for a long time with such an infection and show no clinical signs of disease, you may also see a long-term pattern of random deaths.

These deaths may have nothing to do with other diseases, diet, fish additions, or environmental causes such as water instability.

So if you find that a fish in your aquarium has tested positive for this disease, it is assumed that all the fish in your tank are infected. So you may choose to keep the tank as a closed system and not add any new fish in neither remove any of the fish already in the tank.

You should also take up relevant bio-security precautions, such as wearing gloves to prevent yourself from getting infected. In any immune-compromised environment, depopulation is recommended.

Preventing Fish Tuberculosis 

Mycobacterium SPP is probably one of the most difficult pathogens to detect. This is even with stringent quarantine protocols. If you sacrifice one fish for testing, you may find that another has the same disease.

So maintaining correct quarantine protocols for all new plants and fish added to the aquarium is imperative to avoid catching the infection.

Mycobacterium SPP cannot be treated with UV sterilizers since the infection lies within the fish where UV light cannot penetrate. 

Can Humans Catch TB from Fish?

Yes, humans can catch fish Tuberculosis. In fact, lots of humans are infected with Mycobacterium SPP through contact with infected fish or water.

If you are handling certain species with pointy fins, such as catfish, they can introduce the bacteria through a puncture when you are handling them.

So the disease is also referred to as “fish handlers disease” or “fish tank granuloma.” One of the first signs you’ll notice is localized rashes or pustules on the skin. 

So to avoid this from happening, wear proper protective gear whenever you are handling pointy fish or whenever you have an open wound on your hand.

This bacteria does not cause serious disease in healthy individuals; however, if you are immune-compromised, then you are at higher risk for developing systemic infection. 

If you believe that you could have contracted this infection from an infected system, then speak to a physician immediately. 

Vet Procedures for Fish Tuberculosis

Any fish that die in quarantine should be immediately processed by a vet. You should also know that fish tissue breaks down quickly, so diagnostic testing needs to happen immediately.

If the fish has passed away hours ago and has been nibbled on by tank mates, then it’s not going to be a good candidate for testing.

When it comes to small fish, there is no antemortem diagnosis for fish Tuberculosis. One clinically ill fish will be sacrificed for histopathology testing if there is a suspected infection.

Larger fish, however, may be sampled by performing open coelomic surgery or laparoscopic surgery into the infected cavity. The diagnostic testing will allow granulomas to be visualized and sampled.

In order to confirm the presence of Mycobacterium SPP, specialized acid-fast staining is required.  All fish samples taken should be sent to a lab that is familiar and experienced with fish tissues since they are very different from other pet species. 

Proper sanitization

When it comes to proper sanitization for infected systems, any porous materials like moss or branches should be disposed of. This is because there is no effective or sure-fire way to clean these materials. 

You may, however,  clean small, granular substrate such as sand. Large rocks and stones have too many nooks and crannies to be effectively cleaned and sanitized. Mycobacterium have a specialized outer coating, so choosing the correct disinfectant is also vital. 

It is recommended that you use a 1% Lysol solution as it is the most effective at eliminating systems previously affected by Mycobacterium SPP. A word of caution is that you should never add Lysol to a tank that has fish in it. 


While there is no cure for fish TB in fish, it can be managed with supportive care and reducing considerable stress on your fish.

A good idea as a hobbyist or pet store employee is to take precautions when it comes to handling, adding, or removing fish from a specific reservoir. If you do, however, have a serious fish TB infection in your tank, the best advice is depopulation of the entire tank.

It might sound ominous, but it’s the best thing you can do in the event of a diagnosed outbreak of fish TB in your tank. Secondly, destroy all the contents of the fish tank, including the tank itself. Now, all that’s left to do is start over, this time being more equipped to prevent an outbreak. 

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