Yes, I saw them explain the effects in about a 30 minute show and three vets who worked for Merial. That is the reason I said it was "like a timed release" med. The insect life cycle was explained thoroughly and if what they say is true, this should work against resistance. With 100 to 150 day efficacy it should work toward reducing infestation in your pasture also. Keep in mind that most wormers only kill the worms in the animal, not the ones still incubating in the field. And the effective blood med levels drop off radically after administration. With effective levels staying in the animal, you are still killing those bugs that will incubate and be ingested. Basically, you are interrupting the life cycle of the bugs while eliminating them from the animal. Since the animal is not dropping the eggs in the pasture and the meds are killing those being ingested for 100 to 150 days, it stands to reason that your pasture infestation will be limited to only those worms that are able to survive for 100 days or more. They will survive that and much longer, but with repeated dosages in the animal, it MIGHT reduce your infestation and therefore reduce the worm pressure on your animal. At least that is what they are saying.