For heartworm treatment I use

* Artemisia Combo
* HSII
* Black Walnut
http://www.jeanesholistics.com/heartworm.html

I have been using this treament for many years.

For flea/tick/mosquito prevention. I use this spray.
2 1/2 tsp. (pure) Neem Oil, 3 drops lemongrass oil, 10 drops lavender oil, 5 drops cedarwood oil, 1 tsp. baby oil and water. In a clean spray bottle mix together the five first ingredients into the spray bottle and then fill the rest of the bottle with water. Shake well. Spray on your dog before going outside.