Heartworm Medication Part 1: Truths, Omissions and Profits by JAN RASMUSEN on MARCH 15, 2012  Heartworms are Spread by Mosquitoes.Heartworm Meds are Spread by Fear. It’s getting warmer outside — time for sellers of heartworm medications to start scaring you to death.Television and print ads, which used to push meds only during warm summer months, now urge you to keep your dog on medication year…