Heartworm life cycle

(Dirofilaria immitis)

*** same for dogs and cats ***

We have to begin somewhere and don't worry about the size of the mosquito - not to scale! This picture shows adult heartworms that can live for several years or more in the heart of a dog or cat. The adult heartworms caused a variety of signs of heart and lungs disease due to irritation to the walls of the vessels they live in, mechanical blockage of blood flow and abscesses caused by dead heartworms. The heartworms produce microscopic offspring called microfilaria that are released in the blood supply and are circulated throughout the body.

The microfilaria are ingested by a feeding mosquito. The mosquito swallows the microfilaria and the ingested microfilaria grow to an infective stage larva inside the mosquito (this requires approximately two weeks time).

The heartworm larva escapes the mosquito as it feeds on another animal. The larva are deposited on the skin of this pet.

The larva enter the animal's body through the mosquito's bite wound. Within three months, the larva begin migrating through body tissue to the pet's heart. Approximately six months later, the larva matures to the adult stage heartworm (sometimes reaching 13 inches in length) and begins its reproductive cycle all over again!

Thankfully, heartworm disease is both treatable and more importantly - preventable! Return to more information on heartworm disease by clicking here.