Which leads you to wonder how apes and chimps deal with them -- it's not like there's a Purell plant out there, and it's pretty rare that you see jungle animals in an apron and flip-flops grilling up their steaks for safety's sake (although ... can you imagine?). And as brilliant as chimpanzees are, it's not like they've got culinary schools set up to tackle the dangers of invisible-to-the-naked-eye parasites. Do they?
The Medicine: Trichome Plants
It turns out those dumb chimps pretty much completely figured out parasites on their own.
You see, chimpanzees have a very impressive range of facial expressions ...
"Angry and nauseous commenter."
... so when biologists saw them eating the bitter stem of a certain plant and making absolutely disgusted though hilarious faces, it was clear that they were not doing it because they liked the flavor.
In other words, the general assumption of "If it tastes bad, it must be good for you" wound up applying to chimps, even though you'd think that, as animals, they wouldn't know anything beyond "This is gross, spit it out." And yet there they were, forcing themselves to eat a plant called Vernonia amygdalina like it was medicine they were choking down.