Heartworm disease is a devastating and potentially fatal parasitic infection that affects dogs. Without treatment, a dog with heartworm disease will eventually die. Although heartworm disease can often be treated, prevention is the better option. Unfortunately, heartworm treatment is risky and expensive. Dogs with severe disease may not survive treatment and are often not considered eligible for treatment.

Heartworms are killed with the use of an adulticide. The protocol most vets follow is based upon the recommendations set by the American Heartworm Society. Adulticide therapy has several components. Dogs first undergo diagnostic testing to help determine the severity of heartworm disease. This typically includes lab work and radiographs, but may vary depending on the severity of clinical signs, if any.

To begin the adulticide protocol, the dog is first started on heartworm preventive to kill any microfilariae (heartworm larvae) present. Many vets will use a pre-treatment of antihistamines and anti-inflammatory drugs to prevent a reaction as the larvae die. After the initial dose of heartworm preventive is given, the dog should remain on regular heartworm preventive for the rest of its life (as should all dogs).

The heartworm positive dog is generally started on oral doxycycline or minocycline for the next four weeks. These antibiotics are given to fight bacteria given off by the dying heartworms.

It is also thought to weaken the live heartworms.

Thirty days after the first heartworm preventive was administered, the dog will return to the hospital for the first dose of adulticide. A drug called melarsomine (Immiticide) is injected into a muscle along the lumbar spine and the dog is observed for the day in case of reaction. The same preliminary treatments as before are usually given to prevent reaction (antihistamine and anti-inflammatory injections).

Thirty days later, the dog returns to the hospital and a second melarsomine (Immiticide) injection is given. The dog is typical hospitalized overnight and is given a third melarsomine injection the next day.

Heartworm treatment is risky mainly because of the blood clots that can occur as the worms die. Restriction of the dog's activity is essential throughout treatment and should be strictest during and after adulticide injections. Exercise, excitement and overheating will all increase the likelihood of complications. Vets typically recommend activity restriction for one or two months following heartworm treatment.

When all is said and done, the heartworm treatment protocol may cost as much as $1000-$1500. Even low-cost vet clinics tend to charge $300 or more. When you compare this to the cost of heartworm prevention, it puts things into perspective. The annual cost of prevention ranges from about $35-$250 per year depending on the size of the dog and the brand of prevention chosen.

Important note: Even after a dog has been treated for heartworm disease, re-infection can occur if heartworm prevention is not used!

Dogs that are not eligible for adulticide therapy may be treated with the so-called "slow-kill method." This is not recommended by the American Heartworm Society and is not considered effective. However, it is the only option in certain cases.

If you would like to spare your dog (and your wallet) from the above process, then make sure you are giving heartworm prevention all year long. Educate yourself about heartworms and talk to your vet about the best preventive plan for your dog.