Heartworms by CHRISTINA CHAMBREAU DVM on MAY 19, 2011

[Amateur de chiens - Dog Lovers]

First, you need to know that the “heartworm preventative” does not prevent your dog from becoming infected, it kills the migrating larvae so it prevents adults from living in the heart where they can cause serious heart damage.

http://www.dogsnaturallymagazine.com/heartworms/