I’ve traveled to more than 50 countries on all seven continents and I’ve never been afflicted with worms. I caught giardia one time, but that was when I was hiking in the United States.
I think most travelers’ concerns about worms are overblown. With that said, here is a fairly comprehensive article about dealing with parasites. It might be useful to stockpile a few of the recommended drugs/alternative treatments in case of an emergency.
What’s Bugging You? Dealing With Parasites in Humans
Albendazole, Mebendazole, and Metronidazole are commonly available without prescription in most developing world pharmacies. I have them all in my travel medical kit.