What is Heartworm? Heartworm is a parasitic roundworm
(Dirofilaria immitis) that is spread from host to host through
the bites of mosquitoes. Heartworm is a type of filaria, a small
thread-like worm. It can affect dogs, cats, wolves, coyotes,
foxes, and some other animals, such as ferrets, sea lions, and
even humans. The parasitic worm is called a "heartworm" because
the parasite, in the final reproductive stage of its life cycle,
resides in the heart of its host where it can live for many
years and kill its host through congestive heart failure.
Heartworm infestation is extremely serious for the host;
infected dogs that go untreated can die and even treated dogs
must go through a long period of uncomfortable treatment
(sometimes requiring surgery in advanced cases to remove the
worms from the right ventricle). The best defense against
heartworm is the use of prophylactic treatment given monthly. A
course of heartworm prevention begins with a blood test to see
if the parasite is present. If the dog is parasit