Do you think just trying may help? I mean it isn't too toxic and may at least diminish them.
Right now I am using something (zinc ointment with a drop on iver each time) on my anal area.
What I found was a kind of cross migration between the vag and urethra and I wanted them to come out even if just to lay eggs out rather than in so I did not cover either. It does seem to have an effect. Kind of treating them back and forth for a few days made a real difference.