18/05/2026
Below 57°F (14°C), heartworm transmission stops because mosquitoes cannot support larval development, meaning no infective stage is present. Yet many dogs in low-risk climates are still placed on year-round prevention regardless of actual exposure. This becomes even more important when you consider that resistance exists in certain regions and not all preventatives perform equally. Moxidectin-based products show about 97 to 100 percent effectiveness against resistant strains, while ivermectin products like Heartgard range from about 8 to 37 percent and milbemycin products like Interceptor from about 14 to 36 percent. This highlights that resistance is real but still regional, and that drug choice matters far more than most people realize. It also challenges the idea of a one-size-fits-all approach, since risk depends heavily on climate, mosquito season, and geography. At the same time, natural dewormers are not effective against heartworms because these are blood-borne parasites, not intestinal worms. A more accurate approach is a customized plan based on where a dog lives, their exposure risk, and local resistance patterns, rather than blindly following a universal year-round protocol.
Today we’re covering this quandary on our podcast and how to create a customized plan for your dog based on where you live. Some dogs need year round protection, some dogs need 3 months: knowing the specifics is crucial for protecting against this high risk disease and minimizing drug resistance.
Make sure to download the 60 page PDF before the podcast so you can follow along; we’re covering a lot of ground today!
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