Heartworm Information and Prevention


We hear about heartworm all the time, but do we really know what it is and what risk it has for our pets? Heartworm disease is a serious and potentially fatal disease that is seen all over the world. It is caused by foot-long worms (heartworms) that live in the heart, lungs, and associated blood vessels of affected pets, causing severe lung disease, heart failure, and damage to other organs in the body. Heartworm disease can affect dogs, cats, and ferrets. The heartworm itself can live in other mammals as well that carry the disease.

Dogs are a natural host for heartworms, which means that heartworms that live inside the dog mature into adults, mate, and produce offspring. If untreated, their numbers can increase, and dogs have been known to harbor several hundred worms in their bodies. Heartworm can cause long-term damage to the heart, lungs, and arteries.

How is heartworm transmitted?

The mosquito plays an essential role in the heartworm life cycle. Adult female heartworms living in an infected animal produce baby worms that circulate in the bloodstream. When a mosquito bites and takes blood from an infected animal, it picks up these baby worms. These baby worms develop into larvae worms in 10-14 days. When the infected mosquito bites another animal, the infective larvae spread. It will take 6 months for the larvae to develop into mature adult heartworms. They can live in a dog for 5-7 years which just increases the spread of the disease.

How do I know if my dog is infected?

In the initial stages of the disease, many dogs show few symptoms or no symptoms at all. The longer the heartworms are present the more signs will appear. Signs of heartworm disease may include a mild persistent cough, reluctance to exercise, fatigue after moderate activity, decreased appetite, and weight loss. As the disease progresses, pets may develop heart failure and the appearance of a swollen belly due to excess fluid in the abdomen. Dogs with large numbers of heartworms can develop a sudden blockage of blood flow within the heart leading to a life-threatening form of cardiovascular collapse.

How do I test for the disease?

The early it is found the better for the dog to recover. Testing for heartworm is done through a small blood sample from your pet. The blood is tested for the presence of heartworm proteins.

Dogs should be tested annually for heartworm. Preventative medication should be given monthly. The annual blood work testing is necessary even when animals are on preventatives. This ensures the preventative medication is working. Even missing one dose of a preventative can put your animal at risk.

What happens if my dog tests positive?

First, confirm the diagnosis with an antigen test. This can be done at your vet’s office, and they will determine the best treatment path.

Next, restrict the exercise of your pet. Physical exertion can increase the rate that the heartworms can cause damage to the heart and the lungs. The more severe the symptoms the less activity the dog should have.

Plan for the treatment by stabilizing the disease. Your vet will design a plan that will allow you to treat your animal over a period of months. Once that plan is in place depending on the level of infection successful treatment is possible with full recovery.

Finally, test again once the treatment is complete. Typically, this will happen 9 months after the completion of treatment. To avoid the possibility of your dog contracting heartworm disease again, you will want to administer heartworm prevention year-round for the rest of the dog’s life.

Preventatives are the best way to stop heartworm in your pet. Make sure you schedule it to be given at the same time every month all year round.