Heartworm has become a national problem, and most veterinarians recommend protecting your dog with some kind of regularly administered preventative medication. Preventing hearworm is easy to do for your dog & only requires a monthly pill.
However, some Shelties, Collies, and related breeds have an unusual sensitivity to Ivermectin, the active ingredient in the popular monthly heartworm preventative called Heartguard. The monthly medication Interceptor was developed especially for these sensitive breeds. Its active ingredient is milbemycin, which has been demonstrated safe for Shelties and their relatives. The daily heartworm medication Filaribits is also safe for these dogs, although some concern has been expressed about possible liver damage connected with extra ingredient in Filaribits Plus.
If you have any concerns about which heartworm medication is right for your dog, please check with you vet.