i worm with Ivemectin pour on (found @ farm supply stores... about $15 for 4.5 oz.)... it works on both internal and external parasites. it is not made for chickens so the dosage is as follows... bantam-size bird - 2 eye-dropper drops or 4-5 drops from a syringe/needle dropper... for a full size bird - double that . place drops between shoulders/back of neck, making sure it get directly on the skin (or it will not be absorbed) redose in 10-14 days. worm once a year... don't eat eggs for 2 weeks after application.