Apparently some worm larvae are small enough that they can get in through the pores in your feet. I remember reading that a big part of the parasite elimination campaigns in the south involved convincing people to wear shoes outside more often.
Yeah, we still had some older folk that used outhouses so I wonder if it was through that. I've also considered dogs because we had so many that roamed free. We did grow our food from time to time.
Breaking the reproduction/re-infection cycle was key. Pickup up dog turds did make a difference, so too the widespread use of preventative drugs in pets. Not spitting in the street. Wearing shoes. Bathing in clean/chlorinated water, drinking clean water, proper sewage, and tacking any local infections with serious drugs ... all these things add up to cut the reinfection rate to the point that the parasites stopped spreading.
That or there were eggs on some food you ate.