I'm not so sure about parasites. Honestly, I've not researched any connection they might have to edema or water retention. Although your blood tests look good, have you undergone a pulmonary function test? It might be a good idea to see how your lungs/heart are functioning. Deficiencies in these organs/functions can cause all sorts of difficulties, edema being just one of them.
Talk to your doctors again. See if there is something else to be explored besides diuretics. Perhaps you could research to see what food act naturally as a diuretic and see if they have any positive effect on your symptoms. I'm not a medical professional by any means and defer to the expertise of those who are.
I hope that you begin to feel better soon.
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