Flukes have a very specific look to them. Depending on whether they are decomposed from traveling slowly out your gut or not. If not decomposed, they look like the pictures you can find on any university website. If you are lucky and have taken a stool loosener or do a liver cleanse then you may get one complete and whole with no decomposition. I was lucky enough to have one totally whole and complete with no decomposition come out. Was easy then to identify.
If they are decomposed as they usually are if you use herbs, then they look a bit different. But it is always consistent. Those of us who have had to battle this problem know what to look for specifically. I don't know about the other types of parasites, sometimes food is misinterpreted as parasites. Flukes though, I do know about and it is pretty rampant.