Friends or Enemies?

Although fish are the main cause for human outbreaks, they are not the only organisms infected by Plesiomonas shigelloides. Many animals can be infected, such as cows, dogs, cats and goats. Contamination can be from ingesting contaminated food or water. This bacterium does have to be ingested to have any affect on you. If you’re swimming in a lake with this bacterium, nothing will happen to you unless you swallow some contaminated water.




Plesiomonas shigelloides is capable of living in fish and can lead to a premature death for them. Because fish, depending on the species, either don’t have a stomach or don’t produce enough acid in their stomach to create a low enough pH to kill this bacterium, it can actually survive within the fish. It’s not clear what it does within fish, but if another organism eats that fish, the toxin gets ingested too.


In reptiles and amphibians, this bacterium destroys their livers. It also causes lesions within their mouths, which makes it painful for them to eat their prey. This bacterium can lead to a premature death for reptiles just like it does within fish.


For birds, this bacterium causes hyperaemia, which is excessive blood to the body’s organs. This means there is less circulation of blood throughout the body and metabolic waste doesn’t get carried away as frequently as it should.


As humans, we produce enough acid in our stomach to kill this bacterium. That doesn’t mean we don’t suffer the consequences of the toxin produced, but at least we aren’t a new home for it like the fish. To learn more about how it affects us, check out the toxin page.


Other mammals infected will get sick, but typically just exhibit diarrhea symptoms (similar to humans) and will survive the infection. Most animals other than fish and reptiles are capable of producing enough acid in their stomach to kill off this bacterium, suffer the consequences of the toxin for a short period of time, and go on living a normal life.


Note: This bacterium harms other organisms with its toxin, but does not need other organisms to survive. This means that it does not cause disease by growing on tissue, but rather by releasing its toxin within other organisms.

These are other organisms Plesiomonas shigelloides interacts with, next learn about how the toxin affects them!