Q: I used to live in Michigan, where my dog was on year-round heartworm preventive because the mosquitoes were so bad. I now live in Anchorage, Alaska, and am considering getting a new dog. Veterinarians here say mosquitoes don't carry heartworm. Is this true? We take frequent walks in the woods and often meet other dogs. Can heartworm be passed between dogs? Will preventive medicine hurt my dog if there is not supposed to be a problem? Should I have my dog tested first to be safe?

A: Veterinarians are the best source of information for local disease concerns and I'd defer to those in Anchorage. It is theoretically possible for Alaskan mosquitoes to carry he heartworm, although certain conditions must exist for the parasite to establish a life cycle. Heartworm is not pass ed directly from dog to dog; an intermediate host (mosquito) is necessary.

I recommend putting your dog on one of the newer generation heartworm preventive drugs, which also help head off other internal parasites. These drugs are effective at low doses and safe for the dog. They also help control some parasites that are potentially contagious to human beings.

Proper implementation of a preventive program calls for testing of your dog if it is older that 6 months; younger animals can start without testing.