You have to go after them from both directions and trap them in the middle. Take anti-parasiticals all day, and up the rear end with garlic capsules before bedtime. During the day, you can mix up vermifuge essential oils with olive oil, fill an empty OOO gel cap, and insert, to keep them from biting your butt. The esential oils will make your farts smell better than garlic capsules.
I used to put garlic cloves in my butt to keep the pinworms from biting me and giving me hemorrhoids. Well it will make you need to poop. And I did so in a public bathroom. The smell was unbelievable. I was alone when I dropped the bomb. But someone came in behind me, and said "Oh my God! It smells vile!" That was fifteen years ago, and I am still laughing about it today.
After I switched to essential oils, the same thing happened. But the gal who came in and got a whiff said, "What is that odor?" Big difference, from vile to curiousity. Best to use essential oils so as not to freak people out at work.