I know a girl who is a science teacher and did some research in the Amazon. She had to take many shots in order to fly there (I would think vaccines) and completely duct tape her skin (As well as the other foreigners).
I would think that it is western medicine that requires this and not the people who live there who are immune to the insects and bacteria.
I also knew a guy who took a cruise to Costa Rica and took a tour through the jungle. He was admiring a beautiful flower when it suddenly sprayed some kind of fungus in his face. I worked with him a year after the incident and he was still being treated for it.
Although I would like to think we could live naturally in any environment we desire, I'm not sure if it's truely possible.
The duct tape could've just been a precaution and maybe the locals of Costa Rica would know which plants to stay away from, so it could just be a matter of common sense rather than danger. As far as malaria from mosquitos in African jungle goes, I think that's a completely different story, since I believe the only way to prevent getting it is having sickle cell anemia.