Mycobacteriosis (MB) is a fairly common and often deadly disease that affects many breeds of fish, particularly live-bearers like guppies. Also known as fish tuberculosis (TB), it’s often a stealth disease that affects the internal organs first. An MB infection may be acute or chronic and it may be caused by several strains of gram-positive bacteria.
What is Mycobacteriosis?
Mycobacteriosis, or MB, is a very common and very contagious disease that affects fish. It’s thought to be the most common disease in fish purchased from a pet store. It cannot be cured and it’s often fatal, although there are a few things you can do to prevent an outbreak in your tank. Even more alarming than the fact that the disease can spread throughout your aquarium is the fact that the infection can be transmitted to humans, which results in painful sores.
To make matters worse, mycobacteriosis weakens a guppy’s immune system, which makes your fish more vulnerable to other diseases, particularly fin rot and ich.
Does Your Guppy Have MB?
The bacteria that cause mycobacteriosis or fish tuberculosis is everywhere, including the soil and water. There’s nothing you can do to avoid it and you probably have fish who carry the disease but aren’t affected because they have a healthy immune system and you keep the tank clean. It’s often when water conditions or even diet decline that a fish’s health deteriorates and causes it to develop symptoms of mycobacteriosis.
There are many symptoms of fish TB and they’re often misdiagnosed as a different bacterial disease. Your fish may have fish tuberculosis if it:
- Has a crooked spine and a shrunken stomach
- Seems swollen and overweight
- Has bulging eyes
- Appears emaciated
- Has fading pigmentation
- Seems lethargic or listless
- Hides from other fish or stays in a corner of the tank
- Develops lumps, skin lesions, or hemorrhages after a muscle ruptures
- Shows signs of other bacterial or viral infections like fin rot or ich
Can It Be Treated?
Mycobacteriosis is a very difficult infection to treat because it’s very resistant to antibiotics. Even if it isn’t resistant, the bacteria takes a long time to react to medication and it can remain dormant for months. In many cases, treating the tank with antibiotics only works to kill weaker bacteria, giving the mycobacteriosis the opportunity to thrive.
Preventing Fish Tuberculosis
There are a few things you can do to prevent an outbreak in your tank.
- You can kill bacteria and reduce the amount of mycobacteriosis-causing bacteria in the tank by passing water through a UV device. This will not kill any bacteria in the fish, however.
- Quarantine new fish and treat them with gram-positive bacterial treatment for months before introducing them to the new tank. Starve the fish for 2 days beforehand to reduce bacteria in its gut.
- Boil any infected aquarium equipment for 10 minutes to kill the bacteria.