I am glad to see a lot of good advice going out on heartworm disease in ferrets. With the flooding here in Wisconsin we have the largest number of mosquitos that I have ever seen, and I am really pushing heartworm prevention to all ferrets, indoors and out. My only word of caution is for those of you mixing up your own "heartworm prevention". Ivermectin is a very touchy medication and once mixed should be protected from light (a dark colored bottle). Also I prefer the fresher the better, so mix fresh every year, or sooner. Watch the dates on the bottles of Cattle ivermectin, it won't last you more than a few years. It's no use trying to prevent with a drug that's lost it potency and may even be harmful. If in doubt about mixing or having fresh product - check with your veterinarian. By the way the heartworm prevention dosage is the same for dogs - 6 mcg/kg (mcg is even smaller than a mg). I am actually using Revolution on my own ferrets, and so far I am happy with it (even with all the bad post I'm seeing about it). Carla Christman, DVM [Posted in FML issue 3089]