If you look into the parasitology literature some parasites including Ascaris Lumbricoides are known to infect ppl outside of the tropics. Fact. I never been to tropics but I have it. Yet doctors claim they know better.
Also parasite treatment was grossly underestimated. Many studies on anti- parasite drugs are fundamentally flawed for example, many rely on the egg stool sample testing which is unreliable to prove a cure.
In terms of not being cured ppl are not crazy at all. No anti- parasite med is magic. What many don't know is that parasites evolved to be the ultimate surviving machines... Some will have completely different set of genetics AKA worm mutants. Which are known to be more resistant against anti-parasite drugs today.
But hey docs still believe that saturated fat is bad for you LOL! And we try to teach them about parasites? ROFL!