Based on Article by Jeff Grognet, DVM Dogs in Canada 2008

Heart worm was recognized in North American over hundred years ago.Since then a lot of progress was made but vet’s still find patients with this disease. Some dog owners do not implement prevention programs.If their dogs become infested then the whole dog population is in danger.
Heart worm are eight to ten inches long spaghetti like worms. they feed of nutrients from blood. The larvae are found in mosquitoes - they are ready to infest the next mammalian host. The larva then enters the bloodstream and starts migration process eventually becoming a heart worm in a blood vessel. They can live up to six years. Only few heart worms are actually living in the animal’s heart most of them live in blood vessels in the lung and heart passage. They do not completely block the blood flow but they are obstacles - the heart has to work harder to pump the blood so the result is a heart failure.

A few worms in the artery do not normally trigger symptoms, however if the number rises the dog can have a cough, be reluctant to excersies, may fatigue easier. A heart worm infested dog is thing and has poor muscling and scruffy coat.
Vets use blood tests to determine if the dog is infested with heart worm. If the dog does have a heart worm treatment is complicated and expensive. The options for heart worm prevention are tablets that are give monthly. We used Revolution - that also works well in the light Demodex cases.

* Topical once-a-month parasiticide for dogs.
* Provides systemic treatment against a broad spectrum of external and internal parasites.
Approved Uses
Revolution® (selamectin) is approved for:
* Use in dogs 6 weeks of age or older against the following parasites: adult fleas, flea eggs, heartworm, ear mites, sarcoptic mites, and American dog tick.
* Killing adult fleas and preventing flea eggs from hatching for one month, and indicated for prevention and control of flea infestations (Ctenocephalides felis).
* Prevention of heartworm disease caused by Dirofilaria immitis.
* Treatment and control of ear mite (Otodectes cynotis) infestations.
* Treatment and control of sarcoptic mange (Sarcoptes scabiei).
* Control of American dog tick (Dermacentor variabilis) infestations.
Key Features
* Revolution is a prescription-only medicine, not a pesticide.
* Broad-spectrum protection against most internal and external parasites.
* Kills adult flea and their eggs.
* Fast, simple and easy to use.
* Because of the low-volume dosage size, the solution can be applied in one spot.
* Non-greasy, quick-drying preparation.
* Bathing pet 2 hours after application does not affect efficacy.
* Available in 6 convenient dosage sizes in no-drip disposable tubes