Things don’t always work the way they are supposed to! It is possible for a previous heartworm test to have given a false negative result if the infection was recent. Even if a pet has been on preventative for years, manufacturing errors occur, resulting in ineffective medication. We have also been called by people who have found a stash of pills in a hidden spot, where their pet ran and spit them out after they were “sure” they had swallowed them.
If we did not test annually, the result of all of these situations would be a pet who would carry heartworm disease for years without our knowledge. The end result? A dog or cat who was supposed to be protected, dying from heartworms.
We follow the American Heartworm Society guidelines. This independent panel of parasitologists, publishes recommendations based on the current prevalence of heartworms in the US.