If you live in any location in which there are mosquitos, you should be treating your ferrets for heartworm. Ferrets in Florida should be treated 12 months out of the year. Other parts of the United States can treat heartworms seasonally -- the times of the year that mosquitos can live; typically spring, summer, and fall. One single mosquito bite can give your ferret heartworm. A cure is unlikely. Prevention is they key! I live in the Tampa area and treat my ferrets monthly with a liquid concoction of ivermectin, ferretone, and propylene glycol. This is mixed and prescribed by Dr. Deborah Kemmerer at the West End Animal Hospital in Newberry. Dr. K's web site is http://www.atlantic.net/~weah/ and she has some information in the Ferret FAQ about heartworms and heartworm tests. I just lost my Tigger to a heartworm. She apparently already had the heartworm when I rescued her. When you give your ferret heartworm medication, it will NOT kill any existing heartworms; just prevent new ones from growing. Tigger was a healthy, happy 3-year old who needed routine adrenal surgery. Although the surgery was successful, she died the next day. The necropsy showed a heartworm; Tigger's heart could not take both a heartworm and surgery at the same time. We are heartbroken, but relieved that our other nine ferrets tested negative for heartworms, and we religiously give monthly medication to them all. - Erika and the Tempestuous Ten [Posted in FML issue 2677]