I’m only a year into it, but being in TN we have some experience in parasites. How high are the counts? We rotate wormers to keep from developing immunity. The vet (she has much reindeer experience) leads this conversation when we get high counts and makes a recommendation based on time of year and what we used last.
We rotate Fenbendazol, Levamisole (Prohibit), and Panacure. We try to keep ours at 50 epg or less. When we get a bad run of them we strip the barn to the concrete, spray a mild bleach solution and let it sit, then rinse it out. It’s also important to pick up piles daily.