I have heard there is a new once-a-year shot to prevent heartworms in dogs. Does it really work? Is it safe? The ProHeart 12 injection is the once-a-year heartworm preventative you're talking about.

I have heard there is a once-a-year shot to prevent heartworms in dogs. Does it work? Is it safe? DR. MCMILLAN'S ANSWER: The Proheart 12 injection is the once-a-year heartworm preventative you're ...