You have asked a question that has been argued about all day long in this Water Fasting forum. You read the thread that has 55 replies? When you fast to completion, if you had any parasites to begin with they would be consumed with all the other bad things h in our bodies during the cleansing and healing process that happens when you water fast.
I wouldn't even think twice about parasites because it only causes fear and we are all having a hard enough time fasting without having to worry about parasites!