I guess the dog whisperer doesn't recommend heartworm - here's a clip from his site.
I mainly recommend natural-food diets, colostrum, minimal or no immunization and no monthly wormers or heartworm protection. I recommend also that if there are mosquitoes in your area you use my combination of the blend of the following essential oils; Lemon Grass, Lemon and Eucalyptus oils. Two drops of each per ounce of water and spritz the dogs when they go out in bug infested situations. This mixture works equally well on humans and is my bug repellent of choice for my family and myself. You can order these oils off my website
www.thepetwhisperer.com under the essential oil section.
http://www.thepetwhisperer.com/