I doubt whether they are going to die very fast. A dog study showing that to kill the adult heart worms, it takes 36 weeks of dosing of ivermectin and Dioxcline, and only killed 78% of adult. My effort is just a starting point. However, if you look at the picture in the paper of
Case Report: Failure of Subcutaneous Ivermectin in Treating Strongyloides Hyperinfection
you may realize how poorly the ivermectin was absorbed by oral dose.