Oh there is no doubt they feed on fish tissue, you can see that under a microscope with a fresh sample. Indeed, with many fish, the infection begins deep-seated in the fish's muscle - I have no idea how these protozoans get there though.
Maybe how other creatures work. They start from the inside out after being ingested, or somehow get in the bloodstream. I don't really know either.
If they eat flesh...They must have to eat their way through to the inside. Possibly just a couple do that and then they breed/ multiply inside their food source, the fish's flesh. My thoughts.
Sorry to hear that. I agree to this in a way. I think its something like they get into a digestive system, wound, or small scratch. Working their way through. Some things prefer certain places to be and will travel there. Similar to how some fish diseases/worms can be transferred to humans and travel through them. Many ways infections can start and spread via unique lifecycles. Just not sure how this one does.
I re-read the section in Noga about this. He coyly says it just "invades tissues" without even hinting at a mechanism, no reference either. This bugs me; if it invades the tissues through a scratch, one would think the infection would be seen near the skin's surface, early on. If it went through the oral route, You'd expect the digestive system to show early signs of infection - but it typically just shows up deep in muscle tissue.....
Yes very interesting how some things work. I don't know they got there someway though. Have read other places saying full with red blood cells, some organs not infected but present in samples. I would guess travel to that spot via blood. I wonder though. At any point do they have spores/time in life where their not infectious, or cyst stages under stress? Maybe there but kept in check by immune system. Could a fish egg be infected? Then later fish develop around it being fought by immune system the whole time. Don't know can only speculate.
