That's because the medical community failed big time. First they don't want to deal with it or they are just stupid. No Q about that. Second none of them really proved any effective drug against them. Yes you read that right. Stool testing can't be used as 'cure' evidence. It's pure nonsense. Third they grossly underestimated the survival capabilities of parasites in a host. That's why ppl deal with them for years if not the whole life. When dealing with parasites you must remember that they are evolved for millions of years to ensure survival in a host in almost any given situation apart from the death of the host. And if your own immune system fails/can't deal with something you just shooting in a dark in a hope to hit something. Sorry for one more depressing post but sometimes ppl need to face the brutal truth. You can't run away from it for ever.