There is an antigen test for heart worm. However, ferrets typically do not have enough heart worms to be able to detect the protein they shed into the bloodstream. My foster had several in her heart. I saw this through ultrasound. This is the only way to detect true and accurate confirmation of heart worm in ferrets. The American Heart Worm Society states on their website that heart worm is found in all states now along with mosquitoes being found in every state - no matter how cool/cold etc. In cases where there is sudden, unexpected death of a ferret, heart worm should be considered and would be found in necropsy (autopsy). Proheart5 is the treatment for heart worm in ferrets. The fear of treatment has been that once the heart worms have died they would block/clog the tiny heart valves. This is not always true in every case. Since I did not know my foster had heart worm I did dose her with Revolution monthly without death as the result. The definitive test for heart worm in ferrets remains ultrasound. An ounce of prevention is worth a pound of cure! The American Heart Worm society recommends preventative treatment 12 months out of the year/year round. Sincerely, Lindsey Tootle [Posted in FML 7801]