Parasites (worms and single-celled organisms) are pervasive in certain parts of the world and amoebas are very common in Guatemala where we lived for 1.5 months this summer.
All tagged parasites
10 Ways to Protect Yourself from Getting a Parasite While Traveling
Parasites are more common than you think, especially in Central America and SE Asia, but they're avoidable if you follow these recommendations.