Boston Pet Owners: 8 Symptoms of Heartworms in Dogs

Heartworm disease is a serious and potentially deadly disease that can affect dogs, cats and ferrets, as well as wild canine species. In the US, cases of heartworm disease have been reported in all 50 states, as well as in other parts of the world.

What is Heartworm Disease?

Heartworm disease is caused by parasitic worms called heartworms.  The reason that they’re called heartworms is that they live in the heart, more specifically the pulmonary artery of the heart.  These worms can also infiltrate other parts of the heart and lungs, and if untreated, can cause severe lung disease, blockages of the valves of the heart, as well as damage to other vital organs in the body.

In severely affected dogs, you may see a swollen abdomen due to fluid buildup because the heart cannot effectively circulate blood, or notice a cough, or other signs such as respiratory distress.  Heartworm disease in dogs is known as a silent killer, because it can take months before your dog shows symptoms.

Heartworms are transmitted by mosquitos, which act as vectors and play an important part in the transmission of heartworms to your dog.  Adult female heartworms create infant worms called microfilaria that circulate in the bloodstream of the body.

When a mosquito bites a dog or other canine that has heartworm disease and takes a blood meal, the mosquito ingests the baby worms, which develop and mature into the infective stage of larvae over a period of 10 to 14 days. When the infected mosquito, the vector, bites another dog, cat, or other animal, the infective larvae are injected into the new host through the mosquito’s bite.

Once inside the new host, it takes about six months for the larvae to mature into adult heartworms. Once mature, heartworms can live for five to seven years in dogs, and up to two or three years in cats.

Heartworms can live a long time in your pet, and it’s important to note that with each new mosquito season, more heartworm larvae can be transmitted to your dog.  When veterinarians diagnose heartworm disease, a blood test is run, and this test can detect heartworm antibodies in the blood.  A blood smear can also show microfilaria moving in the blood sample on a slide.