I have no idea where or when I picked up any of the many, many worms and other parasites I've had. I can say that my immume system must have gone down about 2012 which allowed all species to multiply.
I've been battling ever since trying to eliminate as many as I can and hoping my immume system will kick in again soon. Many have multiple parasites, such as myself, cimber38 and hotelparasite.
I could have had many parasites since childhood as I was raised in an unsanitary, rural environment in the SE U.S. I also had multiple dogs for 20+ years.