Very good list.
Airborne -- microscopic eggs can/do float in the air (lid/no-lid flushing toilets comes to mind. Microscopic eggs can float and ride air currents at anytime.
The biggest menace in my opinion is hygiene -- washing hands.
To the original poster, you DON'T have to travel outside of the USA to contract parasites
-- this is a myth. There are plenty of parasites
on the homeland that are more than happy to infect a person!!
I read an article where a couple was visiting the USA picked up a parasitic infection and had to be treated when they returned home. I don't know if the story is true but it is plausible and believable.
Since becoming aware that there is a problem, I observe people A LOT closer! parasites
can be contracted just about everywhere and any place. I watch how easily people can infect themselves without realizing it.
Think about the gardener who is doing some gardening and wipes their face with their hands because it's a hot day. Kaboom -- friendly roundworms!
How about father and son fishing. They bait those hooks with WORMS that may carry microscopic eggs on their bodies. Later they have lunch out on the lake in their put-put boat. They may have even wiped their faces during the midday heat with their hands. Kaboom - roundworm infection!
What about the construction worker who may not have facilities to clean up properly before consuming his 1/2 hr lunch. Kaboom -- microbes of all sorts!
About 10 years ago a survey and inspection was done on the Top 10 Finest Restaurants. All the cooks and workers had dirt and feces under their nails. Kaboom -- don't even want to think about that one!
Someone buys salad items and only "rinses" (or not at all) the vegetables. parasite
eggs are sticky. You're feed the salad mix and eat it happily. Kaboom - roundworms.
A study was done that roaches carry Ascaris
eggs on their bodies. If anyone has a roach problem... Kaboom -- possible Ascaris
Smell flowers from any garden and microscopic eggs along with other things are inhaled. Kaboom!
Children's sandboxes have parasites in them. Kaboom - toxocara, Ascaris
What about the innocent people that pick organic fruit from a tree or vines who eat it on the spot. Kaboom! They also consumed organic little buggers without thinking about it! One person I know who shopped at the health food store thought that everything they bought had been washed and never considered that things fall on the floor, employees' hands weren't always clean, etc.
The lists and scenarios can go on... parasites are everywhere.