Over the last few months, our office has seen several cases of mycobacteria in pet fish, also commonly known as fish tuberculosis. Never heard of it before? Well, here’s everything you need to know:
Mycobacteria spp. aka Fish Tuberculosis
Depending on your fish experience, you may have heard a lot or very little about the potential dangers of fish tuberculosis, also known as mycobacterial spp. infections. This disease can be very hard to diagnose without proper pathology processing and can persist in seemingly healthy systems for years. Clinical signs are very vague and can be augmented by other problems with your tank. Of all the diseases fish can potentially contract, this one can be passed onto HUMANS. Due to the severity of this disease, we’re here to set the record straight and make sure all fish owners know the ins and outs of this disease.
What is mycobacteria?
Mycobacteria is most commonly associated with tuberculous. It persists in almost all aquatic environments as a non-harmful environmental contaminant. Some species, however, can infect fish, including M. marinum, M. fortuitum and M. chelonae. M. marinum can be found in both freshwater and marine environments. It is spread through direct contact and release from the internal organs post-death.
What are the clinical signs of infection with mycobacteria?
Unfortunately, the clinical signs of a mycobacteria infection are very vague. It is most commonly associated with wasting, loss of body condition, lethargy and anorexia. Other signs include scale loss, skin ulcers, a dropsy-like appearance, reproductive problems and a host of secondary infections.
How is a mycobacterial infection diagnosed?
Mycobacteria is diagnosed in fish through a biopsy of internal organs sent to an aquatic pathologist. There are no tests that can confirm mycobacteria in live fish at this time. The presence of mycobacteria is confirmed using an acid-fast stain.
What treatments are available for fish tube?
The saddest part of this infection is that no treatments are available for fish tuberculosis. Fish can persist with this bacteria in low stress environments with good water quality, but will eventually succumb to the disease. It is recommended the entire system be decontaminated with a carefully selected disinfectant that will penetrate the mycobacteria. Not all disinfectants will work with mycobacteria. Prevention is key through proper quarantine and possibly sacrificing some individuals for histopathology screening.
Is mycobacteria dangerous to humans?
Yes. This is one of the fish diseases that can be passed onto humans. Although the disease is rarely life-threatening, the bacteria can easily enter any open cuts or sores that are placed in tank water. Take proper precautions and avoid contact with tank water and do not allow other pets to drink the water.
What do I do if I think my fish may be infected?
It is extremely important that mycobacterial infections be diagnosed as early as possible. Contact your local aquatic veterinarian or aquatic pathologist to get your fish tested. (https://wavma.org or https://fishvets.org) You can request an appointment online from our staff in California. Remember, there is no testing available for live fish, so you may need to sacrifice a sick individual to confirm.
Francis-Floyd, R. 2011. Mycobacterial Infections of Fish. Southern Regional Aquaculture Center.
Francis-Floyd, R & R Yanong. 1999. Mycobacteriosis in Fish. University of Florida IFAS Extension.
6 thoughts on “Mycobacteria in Fish aka Fish Tuberculosis”
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Thank you very much for your unbelievable support. I’m very appreciated.
If my fish have this Mycobacterial Infections and my hands have been in the water siphoned water by mouth never got any in my mouth should I be alarmed
If you are relatively healthy, you should not be concerned, but I would discourage you using your mouth to get a siphon going!
If TB is suspected among a few fish in a school (I have cherry Barbs), should I separate all of the suspected infected fish? What is the likelihood of TB spreading to some/all of the “healthy” fish? Will the entire school eventually succumb to TB?
If mycobacteria has been confirmed in your tank, it is assumed that all fish and inverts in the tank are also possibly infected. It is hard to know if it will be the primary or secondary cause of death without diagnostics.