Re: How to approach a parasite infection
Where (geographic part of the world) is this lake located? Various species of schistosomes worms (one of the trematodees, technically a fluke, but more conventional round worm shaped than flat worm shaped) infect via their metacercaria larval form attacking swimmers in freshwater lakes and rivers and essentially "dissolving" their way into the skin to get inside the body. Supposedly there aren't supposed to be any of the notorious human-infecTing species of schistosomes (S. mansoni, S. haematobium, S. japonicum, etc, natively found in North America, but in the USA there is a lot of an animal schistosoma species, named Heterobilharzia Americana which normally infect raccoons, and dogs (and likely many other mammals too) that are *supposedly* not able to infect humans other than maybe causing some mild "swimmers itch" rash that supposedly goes away after a while, but I've got my own suspicions that what's written about them in biology and medical textbooks could be seriously out of date due to mutations/hybridizations or environmental adaptations of some animal species of schistosoma worms, or which there are dozens/scores of different specific species that parasitize birds, cattle, all sorts of other animals.
Getting a suspected
parasite infectIon after swimming in a lake anywhere on the planet, and any possible associated skin rash-type conditiion that suspiciously seems to be a cause & effect related effect to that lake swimming, just sounds like textbook cases of some sort of schistosoma to me.