To briefly put an end to Enache's umm, contribution, so we can move on here, since he is not the first person to come into the discussion having done no research and act like some expert because they read something on wikipedia.
The "annually" quote, comes from wikipedia. Anything from wikipedia requires a source.
The source on wikipedia (I'll save Enache the trouble of looking it up himself) as was established a year ago is the Carter foundation.
The Carter Foundation is a charity which deals with poor people who live in areas of high risk of getting reinfected with Bilharzia. It recommends annual treatment because it is cheaper and more efficient to simply give everyone living in these areas, yearly doses of Prazanquitel (which contrary to what Froome says has few side effects) than it is to test everyone for Bilharzia all the time.
Froome lives in Monaco and races in Europe. Neither of these are areas of high risk, or since they aren't located in the tropics any risk. He has the money and the means to afford checkups and treatments to actually tell when he has Bilharzia, his profession requires he know immediately and his team and governing body do it for him anyway. Since he doesn't step into Bilharzia infected lakes, on his day to day, he has no way of getting reinfected in the first place.
Until Froome becomes a member of a Kenyan lake tribe, who needs to risk getting Bilharzia every day to meet subsistance, the findings and recommendations of the Carter Foundation, do not apply to him, no more than they do to anyone on this forum.
Now lets, move on.