But just be very aware, the vet also says that the old every 6-8 weeks program isn't the best for every horse. Rather than just shoving paste down our horses at regularly scheduled intervals, we need to look at what kind of risk factors there are in their situation for reinfection and each individual horse's resistance to parasites to plan a deworming program for THAT horse. Strategic deworming programs are now the recommendation.
And just to clarify, even though ivermectin is currently effective and so can be used as the main drug in a deworming program we still need to limit it's use to only when necessary. This is because frequent use leads to increased risk of the parasites developing a resistance to it. And this is already starting----a study done in KY last year showed that strongyles on one farm were resistant to ivermectin.