http://ezinearticles.com/?Heartworm-...ion&id=2350468

Some excerpts:

"Most holistic practitioners and alternative veterinarians will explain
that the healthy pet, that eats a good diet, is vaccine free, and is not
currently on any heartworm medication or chemical flea and tick
preventatives, most likely has a strong immune system that will fight
off heartworm. None of the larvae will survive and become adults. In the
unlikely event that some of the larvae should manage to survive to
adulthood, it is not the death sentence that many vets and
pharmaceutical companies want us to believe. A truly healthy dog will
not be a hospitable host. His strong immune system will weaken
heartworms and the pet should be able to fight them off with no lasting
ill effects to his health.

"Dr. William Falconer, a homeopathic veterinarian in Austin, Texas
states: "The heartworm has been out there forever as far as we know, but
we don't read reports of wolves and coyotes being wiped out by
heartworm, and yet domestic dogs are falling prey to it.

"The reason why our domesticated pets are falling prey to heartworms is
because they have weakened immune systems. Canines in the wild are
eating raw meat and bones and are never exposed to chemical treatments.
Their strong immune systems fight off heartworm in the larvae stage, or
very few heartworms survive and they do not threaten their hosts' lives."