Heartworm disease in dogs is caused by infection with Dirofilaria immitis, a worm that may grow to be 14 inches long!
Heartworms live in the heart and arteries of the lungs of its host causing heart failure and possibly causing damage to the liver and kidneys.
These parasites can infect dogs of any age, sex, or breed and can infect indoor dogs and well as dogs that spend most of their time outdoors.
A dog infected with heartworm disease may or may not ever exhibit any indication of having the disease. It is of utmost importance that every dog be placed on heartworm preventative.