In Texas, heartworm testing should be performed on every dog, every year. A comment that we routinely hear is: “My pet has never missed a dose of heartworm medicine, do I still really need to have him tested every year?” The answer is a resounding “yes!” No preventatives are 100% effective 100% of the time. There are too many variables involved. If you give heartworm preventative medication to an unknowingly heartworm positive dog, serious problems and even death can occur! Heartworms are easily spread by mosquitoes (who can infect your pet with one bite!), and heartworm disease is devastating to those pets who acquire it. The heartworm test that we use at Trinity Pet Hospital is performed by Idexx Laboratories. In case of a positive result, they will duplicate the test to verify the result and insure that a false positive result does not occur.