Stronghold covers heartworms but not ticks. if you use Stronghold, you shouldn't need a heartworm treatment, but you would need a treatment for ticks, . Simparica Trio covers Ticks, fleas as well as heartworms, so normally you wouldn't need any other treatment when you are using Sinparica Trio.

Simparica Trio has been demonstrated safe for dogs as young as 8 weeks old