I have an opinion on this, although I am far from qualified to know definately.
It sounds possible that the cleansing could have damaged the [parasites] enough so large amounts of it's antigens {identification molecules} may have been released. This may have alerted your immune-system which had previously been "asleep at the wheel". It could bring upon a sudden an intense illness for at least 24 hours. After that, there may be yellowish substance coming out in your stool, which would be a positive indication. {just a personal opinion}. Shroom