We eradicated hookworm by getting everyone shoes.
Discussion
Properly treating sewage is the second way that hookworm was eradicated: the lifecycle of the parasite includes spread via feces. But shoes were the first effective measure.
A big part of why people culturally wore shoes was probably hookworm infestations. Over a lifetime you're more likely to survive if you and the people around you consistently wear shoes.
Probably the first ten years of my life I almost never wore shoes except for school and church. Spent all day in the woods.
Never got hookworms.
Because you lived in a community where enough other people wore shoes, and has functioning sewage systems, that hookworm had been eradicated.
Like vaccination, you only need a certain % taking counter measures for the remainder to be protected.