My philosophy is to teach my clients what is good health and what their choices are, and then allow them to make the choice for their family. I then support that choice. Here are the choices I offer clients for prevention of heartworm. FYI - I use choice c for my dogs.
a. No specific preventative used. Blood test every 6 months.
b. *Homeopathic Nosode (remedy), monthly in mosquito season. Blood test every year.
c. *Ivermectin-based meds (Heartgard, Iverhart, Tri-Heart, etc) every 3 months, all year. Blood test every 1-3 years.
*In 15+ years of recommending these protocols, in an effort to lower toxic burden while maintaining adequate protection, no patient has ever had failure of protection (positive heartworm test).