Heartworms

What Is Heartworm?

A heartworm is a parasitic worm (Dirofilaria immitis) that lives in the heart and pulmonary arteries of an infected animal. The worms travel through the bloodstream—harming arteries and vital organs as they go—ultimately completing their journey to the vessels of the lung and the heart chamber about six months after the initial infection. Several hundred worms can live in one dog for five to seven years. Heartworm disease is serious, and can be fatal.

What Causes Heartworm?

Heartworms are transmitted from animal to animal by mosquitoes. The lifecycle of the heartworm is complex. An animal must carry at least two heartworms (a male and a female) in order for female heartworms to reproduce. Females produce babies, called “microfilaria,” which are shed into an animal’s bloodstream but are not capable of directly causing heartworm without first passing through a mosquito. The microfilariae must be taken up by biting mosquitoes, and transform into infective larvae over a two-week period inside the insect. When the mosquito next bites a susceptible animal, the infective larvae enter the tissues and begin a migration into the blood vessels. (Information from the ASPCA)

Click here for informational Heartworm Brochure on Testing for Heartworm Disease

For more information on heartworm disease please visit the American Heartworm Societey.