The Dog Dame: The Hoopla About Heartworm

You've probably heard about Heartworms and give your dog a prescription preventative that you got at your vet's office, but how much do you actually know about Heartworms?

Diagram of heart infected by heartworms

Do you know how heartworms are transmitted? You may be surprised to find out that Heartworms are only transmitted by mosquitoes! This is why it's so important to use a flea/tick preventive that also prevents mosquito bites, in addition to the monthly Heartworm preventative. Everyone has their pwn preferences regarding which Heartworm preventative and Flea/Tick preventative is the best. Heartworm is a problem in all fifty states, so there is no area that's safe. Personally, I have chosen to use Sentinel for Heartworm preventation because it also protects against roundworms, hookworms, fleas, and whipworms. I use K9 Advantix II because it repels and kills fleas, ticks, and mosquitoes, plus repels lice and biting flies.

It takes about seven months from the time your dog is bitten by an infected mosquito for the Heartworm larvae to mature into adults. Once that happens, they lodge in the heart, lungs, and surrounding blood vessels. Adult Heartworms can live for 5-7 years, and will slowly kill your dog if left untreated.

Heartworm Lifecycle

An ounce of prevention is better than a pound of cure. A year's supply of Heartworm prevenative typically costs $50-120, depending on the weight of the dog. Your vet will require an annual bloodtest to ensure that your dog has not been infected. Conversely, treatment is an injectable called Immiticide, which is an arsenic-based drug that is administered 2-3 times to kill the adults. With the bloodwork, xrays, other prep and Immiticide, you're easily looking at $1000 or more. There's no guarantee that it will work, and it's very hard on the dog receiving treatment.

The symptoms don't show up right away, but include fatigue and coughing. While this blog focuses on dogs, Heartworm disease also affects cats, and mosquitoes spread the disease. Heartworms destroy the tissue where they live. Left untreated, Heartworm disease will progress and damage the dog's heart, lungs, liver, and kidney's, eventually causing death.

There are four stages of Heartworm Disease:

Stage 1: No symptoms or mild symptoms such as an occasional cough.
Stage 2: Mild to moderate symptoms such as an occasional cough and tiredness after moderate activity.
Stage 3: General loss of body condition, a persistent cough, and tiredness after mild activity. Trouble breathing and signs of heart failure are common. For class 2 and 3 heartworm disease, heart and lung changes are usually seen on chest x-rays.
Stage 4: Also called caval syndrome. There is such a heavy worm burden that blood flowing back to the heart is physically blocked by a large mass of worms. Caval syndrome is life-threatening and quick surgical removal of the heartworms is the only treatment option. The surgery is risky, and even with surgery, most dogs with caval syndrome die.

There are a lot of Heartworm prevention products available. Ultimately, you have to choose what is best for your dog. This chart helps to clarify their differences: