Heartworms in Dogs: Facts and Myths
WebMD separates the facts from fiction about canine heartworms.
Q: Why do I have to keep my dog quiet during the several months he’s
being treated for heartworms?
A: After treatment, the worms begin to die. And as they die, they break up
into pieces, which can cause a blockage of the pulmonary vessels and cause
death. That’s why dogs have to be kept quiet during the treatment and then for
several months afterward. Studies have shown that most of the dogs that die
after heartworm treatment do so because the owners let them
exercise. It’s not due to the drug itself.
Q: If my dog is diagnosed with heartworms, can I just give him his
monthly preventative instead of having him go through treatment? Won’t that
kill his heartworms?
A: Studies have shown that if you use ivermectin, the common preventative,
on a monthly basis in a dog with heartworm disease, after about two years
you’ll kill off most of the dog’s young heartworms. The problem is, in the
meantime, all of those heartworms are doing permanent damage to the heart and
But if there’s no way someone can afford the actual treatment, at least
using the preventative on a monthly basis could be a lesser alternative.
Q: Can I skip giving my dog his preventative during colder months, when
there aren’t any mosquitoes?
A: The American Heartworm Society recommends year-round heartworm
prevention. One reason is, there’s already a serious problem with people
forgetting to give their dogs the heartworm preventatives. It’s a universal
problem. Now if you use it year-round, and you miss a month, your dog will
probably still be protected. But if you miss more than one or two months your
dog could become infected.
The other reason not to stop is that many of the preventatives today also
include an intestinal parasite control for roundworms, whipworms, or tapeworms. You want your dog to be protected against
those at all times.
Q: If I don’t treat my dog with heartworms, will he “outgrow” his