Heartworm Basics

Heartworm disease is a serious and potentially fatal disease in pets. Foot-long worms that live in the heart, lungs and associated blood vessels of affected pets cause heartworm disease. Heartworms cause severe lung disease, heart failure and damage to other organs in the body.

Dogs are the natural host for heartworms. They live inside the dog, mature into adults, mate and produce offspring. If left untreated, their numbers can increase. Several hundred worms can be harbored in a dog’s body. Heartworm disease causes lasting damage to the heart, lungs and arteries. The dog’s health and quality of life can be affected long after the parasites are gone. For this reason, heartworm prevention is by far the best option. Treatment—when needed—should be administered as early in the course of the disease as possible.

Heartworm Life Cycle

Adult female heartworms living in an infected animal produce microscopic baby worms called microfilaria. The microfilaria circulate in the bloodstream. When a mosquito bites and takes a blood meal from an infected animal, it picks up these baby worms. The babies develop and mature into “infective stage” larvae over a period of 10 to 14 days. Then, the infected mosquito bites another unprotected animal and the larvae are deposited onto the surface of the animal’s skin. The larvae then enter the new host through the mosquito’s bite wound. Once inside a new host, it takes approximately 6 months for the larvae to develop into adult heartworms. Each mosquito season can lead to an increasing number of worms in an infected pet.

Is My Pet at Risk

Even if heartworms do not seem to be a problem in your local area, there are many factors to consider. Your community may have a greater incidence of heartworm disease than you realize. Neglected dogs and some wildlife can be carriers of heartworms. Heartworm disease is also spreading to new regions of the country each year. The wind can blow mosquitoes great distances. Relocating pets to previously uninfected areas also contribute to the spread of the disease.

Heartworm disease has been diagnosed in all 50 states. And risk factors are impossible to predict. Rates of infections can vary dramatically from year to year—even within communities. And because infected mosquitoes can come inside, both outdoor and indoor pets are at risk.

Heartworm Testing

Heartworm disease is a serious, progressive disease. The disease needs to be detected early to give the pet the best chance to recover. When a dog or cat is infected with heartworms there are few, if any, early signs of disease. So detecting their presence with a heartworm test is important. The test requires just a small blood sample from your pet. It works by detecting the presence of heartworm proteins. Results are obtained within a day.

Annual testing is necessary in dogs that have not been given prevention or have been given prevention inconsistently. Also, dogs that have been given prevention consistently should be tested every other year. This ensures that the prevention program is working. Dogs can still become infected even though heartworm medications are highly effective . If you miss just one dose of a monthly medication—or give it late—it can leave your dog unprotected. Even if you give the medication as recommended, your dog may spit out or vomit a heartworm pill. Also, your dog may rub off a topical medication. You won’t know your dog needs treatment if you don’t get your dog tested.

Heartworm Treatment

No one wants to hear that their dog has heartworm. The good news is that most infected dogs can be successfully treated. The goal is to first stabilize your dog if he is showing signs of disease. The second step is to kill all adult and immature worms while keeping the side effects of treatment to a minimum.

Here’s what you should expect if your dog tests positive:

Restrict Exercise

This requirement might be difficult to adhere to. It can be especially hard if your dog is accustomed to being active. But your dog’s normal physical activities must be restricted. Physical exertion increases the rate at which the heartworms cause damage in the heart and lungs. The more severe the symptoms, the less activity your dog should have.

Stabilize your dog’s disease

Before actual heartworm treatment can begin your dog’s condition may need to be stabilized. In severe cases of heartworm disease, the process can take several months.

Administer treatment

Your veterinarian will recommend a treatment protocol. This will involve several steps. The American Heartworm Society has guidelines for developing this plan of attack. Dogs with no signs or mild signs of heartworm disease have a high success rate with treatment. More severe disease can also be successfully treated. But the possibility of complications is greater. The severity of heartworm disease does not always correlate with the severity of symptoms. So dogs with many worms may have no symptoms early in the course of the disease.

Test and prevent

Your veterinarian will perform a heartworm test approximately 6 months after treatment. This is to confirm that all heartworms have been eliminated. You will want to give heartworm prevention year-round for the rest of his life. It will avoid your dog contracting heartworm disease again. The cost of heartworm prevention is far less than the cost of treatment.