I question many theories and always in the back of my mind...
dental problems? it may contribute..but what about these young babies and children, no dental work ..was it passed through breast milk, the cord, or the water in formula?
They play in dirt..okay get the point
we garden, we were unaware of the magnitude of their presence and how easily we pick them up..EVERYWHERE. door knobs, walking barefoot anywhere today is very dangerous..some of these parasites multiply at a rapid pace where others are present and are silent and within without our knowledge for decades.
I can only assume..it will always be guess work..but it is true we can pick up another species anytime, anyday, again and again.