It bothers me that the doctor thinks there is no concern because the child seems fine. Uh... parasites aren't celibate. The time to kill them is before they cause a noticeable change in his health - and yours.
The fact that he is in good outward health means you don't have to panic. You have time to kill those things before there is serious trouble from them.
Don't be too shocked. At least you found out about your parasits, most people are clueless. The chances are you all have other parasites too, sad to say. See the cayenne pepper challenge test in the link below.