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Can I Catch Tuberculosis From My Pet Fish?

Jana worked in animal welfare with abused and unwanted pets. She loves sharing her hands-on experience regarding domestic and wild critters.

Guppies are more susceptible to fish TB than many other fish. Learn more about fish tuberculosis and how it compares to TB in humans, including how it can cross the species barrier and infect humans.

Guppies are more susceptible to fish TB than many other fish. Learn more about fish tuberculosis and how it compares to TB in humans, including how it can cross the species barrier and infect humans.

Fish Tuberculosis

Human TB is a serious condition. At the moment, its treatment remains long and difficult. The disease scars lung tissue and can lead to death. Interrupted treatment can result in immunity against medication and, unfortunately, there's also a strain of TB that's naturally resistant to drugs.'

This is what we'll be covering in this article:

  1. The differences between human and fish tuberculosis
  2. Where fish TB comes from and how it infects a tank
  3. How fish TB crosses the species barrier
  4. Species affected by the disease
  5. Symptoms in humans and fish
  6. Treatment and prevention

The Difference Between Tuberculosis in Fish and Humans

The highly infectious tuberculosis that remains an epidemic in many countries is not the same thing that affects fish. That's the good news; it's not actually tuberculosis. Both diseases are caused by closely related bacteria. Human TB results from Mycobacterium tuberculosis and fish TB from Mycobacterium marinum.

The bad news is that it's indeed zoonotic (a disease that can jump from animals to people). Fish TB ravages an aquarium and causes persistent skin infections in humans. When it blooms in a person, it's also called “Aquarium Granuloma” or “Fish Tank Granuloma.”

Where Does Pet Fish Tuberculosis Come From?

You have a great collection of fish. This healthy shoal has always enjoyed a clean tank and good food. Suddenly, the fish sicken, and a paper cut on one of your fingers develops an agonizing infection. Out of the blue, your aquarium has tuberculosis. How did that happen? Unfortunately, fish TB can sneak past the unwary owner. Here's how:

  • Adding new, infected fish (symptoms can be delayed and make a fish appear healthy)
  • The new fish is healthy, but the bacterium arrives in the bag of water it's sold in
  • Contaminated commercial food
  • Using another keeper's contaminated equipment

M. marinum can live in a tank and not cause wholesale destruction. It's most likely to happen when the bacterium enters a wound, the fish are genetically weak, the fish already suffer from stress or other bacterial infections or the fish live in substandard conditions.

The Siamese Fighter is among the species that are vulnerable to fish TB. They are often kept in small, ornamental vases that cause stress, making them less able to fight off an infection.

The Siamese Fighter is among the species that are vulnerable to fish TB. They are often kept in small, ornamental vases that cause stress, making them less able to fight off an infection.

The Symptoms of Fish Tuberculosis

It's important to understand that fish TB must be correctly diagnosed. There are other conditions and diseases with similar or identical symptoms. Misdiagnosis leads to the wrong treatment and possibly losing the fish to factors other than M. marinum. Classic symptoms of fish TB are listed below.

  • A tendency to thin has earned fish TB the nickname of the “Wasting Disease” and is often the only symptom that shows
  • White growths or lesions on the body
  • The loss of scales
  • Discolouration of scales
  • Deformities, especially along the spine
  • Dropsy
  • Ulcers on the flanks or head
  • Bulging eyes, one or both
  • Abnormal behaviour

Humans normally catch M. marinum while cleaning a tank if there's some kind of wound on the hand. The bacterium enters the skin and causes purple lesions. There's never been a case of human-to-human transmission of fish TB, which is treatable with antibiotics.

How to Treat Fish TB

M. marinum has one thing in common with human TB; it's long and difficult to treat. Unfortunately, most antibacterial products bought over the counter won't be enough. Once the disease is positively identified, sometimes with the help of a veterinarian, the owner needs to prepare for months of changes, medication and sober expectations. For this reason, many choose to make a clean break and start fresh, with new stock and an aquarium. But for those who don't wish to discard equipment nor euthanize fish, there are options.

The ever-popular Gouramis also develop the condition.

The ever-popular Gouramis also develop the condition.

1. The Hospital Tank

Any serious fish hobbyist must eventually own a separate “hospital tank” to quarantine symptomatic fish. To prevent cross-contamination, maintenance is done with equipment never shared with the main aquarium. The TB fish must feel as stress-free as possible since stress can push it past the point of saving. If it loves vegetation or hiding places, make sure there are plenty of them. Ensure water conditions and temperature suit the species and then place the fish inside for observation, treatment or both. A written log can track the progress of the patient.

2. The Main Tank

After removing sick fish from the main tank, decide on whether to cleanse the main tank or not. If the other fish are clearly healthy, the only step some owners prefer is to keep them under observation. However, most people prefer to not take any chances. Substrate and plants are replaced, the tank and equipment are sterilized and the fish can also be given a supplement or treatment to keep them in peak condition.

3. The Right Medication

There's no way around this one. If you skip the correct antibiotics and use cheap pet store products or home remedies, the survival rate shrinks like its being paid. Three of the best antibiotic therapies available for fish TB are Neomycin, Kanamycin and Isoniazid. However, you need professional medical advice on how to administer them and in what combination.

4. Realistic Expectations

M. marinum is difficult to treat, period. Under the best of conditions, survival expectations are below fifty percent. Stress, poor immunity and incorrect tank conditions can make treatment useless. If you have a hospital tank with optimal conditions, good food and the right antibiotic program, then do what you can. In addition, don't expect treatment to last a few days or weeks. Fighting fish TB can take three or four months of steadfast adherence to your regime.

How to Prevent Fish TB

Three things can prevent a lot of heartache and expenses:

  1. Correct conditions: A healthy fish goes a long way to fight off this zoonotic bother, so make sure the environment is perfect: temperature, oxygen, PH levels, cleanliness and no overcrowding.
  2. A balanced diet: Feed it the best food you can afford—and no, a flakes-only diet is not healthy.
  3. Careful observation: A sharp eye is needed to pick up on symptoms as early as possible in order to remove a fish to the hospital tank the moment it looks off. You also need that eye when looking to purchase disease-free fish (try to avoid pet stores). When bringing home a new pet, place it in a separate quarantine tank for a few weeks just to make sure.

Protecting Yourself

A human infection can take months to cure, so prevention for yourself is just as important. Always wear gloves during tank maintenance.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

Questions & Answers

Question: I just was given about fifteen Mbuna Cichlids. I noticed they all had slightly sunken bellies, but act normal. I treated them with a general cure by API, and in the middle of treatment, they still look the same. I was going to treat their food with metroplex by Seachem, but if it's fish TB, I don't know what to do, or if it's worth it. I'm not even sure how to clean the aquarium filters or if I should treat the whole aquarium and get rid of the fish. What should I do?

Answer: I would first contact the previous owner. Find out more about the water conditions, previous illnesses, food type and food amount your pets had at their old home. See if you're doing something that might be too much of a change - sometimes, the problem is as simple as feeding them a little bit more (if the previous owner fed them more).

It's a good sign that they're active and behaving normally. However, do not add more fish until this problem goes either way. Unfortunately, that's the reality. It's very hard to know if this is TB. The sunken belly could be a positive TB symptom. However, it's also a symptom of being underfed, suffering from an internal parasite or skinny disease, which usually comes with lethargy.

Additionally, if you have other tanks, do not share any equipment with this tank just in case it's something infectious. As long as you work with the 15 cichlids, wear gloves when you need to touch the water. Fish TB can infect a human. You won't get seriously ill, but the condition is painful and requires medical intervention.

If this is fish TB, the condition will worsen, and then there will be no doubt. You'll notice lesions, scales falling off, fish getting thinner and even crooked spines in some cases. If you suspect an internal parasite, choose a good product to treat them with.

For now, just monitor your fish. As long as they remain active and healthy, there is still a chance that they might survive. However, as soon as you realize that this is fish TB, you'll have to decide to euthanize. If you decide to end things, contact a vet for advice on how to do this humanely (flushing them down the toilet is not a quick death). Unfortunately, it's safer to throw away filters that came into contact with fish TB. You don't want to risk your next batch of pets. The entire tank also needs to be sterilized with a strong bleach-water solution.

Question: Is fish TB contagious to other fish?

Answer: Fish tuberculosis is not exclusive to a single species of fish. It is more common in some, but more likely because those species are more often kept than others. This disease can also jump to humans. That is why it is very important to always clean the aquarium using gloves, especially when you have open wounds or just a scratch. All it takes for fish TB to jump to a person is a small skin opening. Fish TB also infects everything else in a tank, including the ornaments, equipment, and gravel.

Question: My local fish person (not a big store franchise) looked at pictures of my Betta, and the first thing he said was, "Fish TB." The fish seems in good shape, except for clear globules on his top fin. Can I upload a picture of your opinion? He also told me I could remove part of the afflicted fin and this should give him some time.

Answer: It's always best to confirm symptoms with a vet. This is the only way you'll know for sure whether this is TB, or something else entirely. Also, only consider removing fin parts when a vet recommends such a procedure and then let a professional handle it. Fish are slippery and programmed to thrash when scared. This could cause severe injury should one try to remove something, and the fish makes an unexpected move.

Question: Should aquarium plants be tossed out after an outbreak of TB in my tank?

Answer: Unfortunately, yes. TB remains highly infections and clings to everything in a tank. Traces of it will stick to plants, ornaments, and equipment. It's best to just replace everything. This way you'll know that another TB infection is unlikely. The aquarium itself is often too expensive to replace so just clean it properly.

© 2018 Jana Louise Smit

Comments on November 29, 2018:

Thanks this was helpful

Jana Louise Smit (author) from South Africa on August 12, 2018:

Thank you, Savanna!

Savanna H from Texas on August 08, 2018:

This is very informative! Thank you.