Can I chime in here... if you have not found actual worms, there might be a different cause. Itchy bum can also be casued by candida and bacteria. I also have "pruritus ani" AND not just there but other intimate areas. I have been tested for yeast and all they found was GBS. I know I have GBS from prenatal testing and I know that the only times I wasn't suffering from the itching is when I gave birth because they gave me IV anitibiotics. So that took care of it for a few months and then they recolonized...every time. I've had 4 kids, same story all the time. I have not been able to get rid of it ( parasites or bacteria whatever) with ANYTHING so far, but would not want abx again. What gives me relief is coconut oil mixed with lavender oil or tea tree oil or garlic oil(stinky), but it has not cured the condition.
Anyway, if you don't see improvement after parasite cleansing, it could be something else.