The issue here is generalizing parasites (e.g. putting them into one category) which is a mistake. There are many forms of parasites which means different immune responses, furthermore there are many who employ defense mechanisms that others cannot. Malaria would be one such example, they use DNA coding to 'learn' which substance is killing off the community. Results using both artemesia along with pharma proves to be the best combination, wheras using only one of the substances will have little effect because of adapation by the parasite, there is no proof that improving terrain would actually kill plasmodium, however there are reports of people living with the parasite (e.g. not killing them).
There are probably cases in which bolstering the terrain may indeed eliminate parasites but I would think this would be on the lower level, whereas there are species that can evoke massive damage. In my opinion the internet is filled with lots of dangerous information concerning parasites and give simple answers to sometimes difficult problems.