We used Ivermectin for many years in Ranching for parasite control. We normally gave it in the fall to our cattle and horses. It can be given orally, intramuscularly, or just poured on the back. It kills a wide range of parasites including lice and ticks, Warbles (which is also called screwworms or Bots from Botflies), several types of internal worms like pin worms and round worms, and many other vermin that infest livestock.
You should be able to get Ivermectin at a veterinarian supply store and it used to be over the counter but who knows now, now that it is known to be effective for Covid-19 (if there really is such a thing). Dosage should be on the bottle for the way you want to apply it, and if I recall, I think you give it according to weight to most any mammal. It was also very inexpensive then, but if it is now known to be given to humans it might not be so cheap or so available, so be sure to wear your cowboy hat and smell like a barnyard when you inquire. LOL!!! This is not a recommendation, just information, so please DYODD.