What do heartworms eat?

Heartworms are parasitic worms that live in dogs. They have a complicated life cycle which includes one stage of development in the gut of mosquitoes, then a larval stage in the skin and capillaries of dogs, then an adult stage in the pulmonary veins of a dog. These parasites were given the name "heartworms" because they swim against the current of blood flow in the major lung blood vessels, and when a dog with heartworms dies the worms end up swimming back into the right side of the heart where they are found on post-mortem necropsies.

The good news is, there are quite effective heartworm preventatives on the market currently, in both a monthly oral tablet as well as a monthly topical spot-on liquid. The bad news is, once a mature heartworm infestation is present in your dog, the treatment is dangerous, expensive and in some cases lethal to the dog.