Heartworm Disease

Heartworm disease in dogs (and cats) is a recognized risk in all 50 states. Not only is it recognized in all 50 states, but it has also been diagnosed in every season. There have been many positive diagnoses here in Clatsop County in recent years, though no one knows exactly how many or where the “hotspots” are. Simply put, heartworm disease is caused by adult parasitic roundworms that reside in the heart and related vessels and cause serious illness (including death) of your animal by causing heart and/or lung failure.

Dogs (and cats) get heartworm disease by being bitten by a mosquito that is carrying the infective heartworm larvae. There is no way of knowing which mosquitoes are infected. It only takes one bite from and infected mosquito and there could be adult heartworms causing disease in your animals six to seven months later. The heartworm (Dirofilaria immitus) is a specific type of roundworm that needs a flying insect to transport it from animal to animal. Interestingly, it doesn’t always go from dog to dog. It can go from cat to dog, fox to dog, dog to cat, sea lion to dog or any combination of susceptible animals. Certainly the plethora of marsh lands and wetlands that surround us lead to a lot of potentially infective mosquitoes to transport the immature heartworms and cause disease.

Heartworm disease is diagnosed using a simple “snap” test at your veterinary office and requires a small blood sample to be obtained from your pet prior to the test. The procedure tests for a protein (antigen) produced by adult heartworms that circulate in the blood.

If the test is negative, a heartworm preventative program should be started and maintained throughout the year. An annual test is a very good idea, though not often required. Ideally the heartworm preventative that is chosen will not only prevent heartworm infection but will treat intestinal roundworms and fleas as well. One note of caution, not all heartworm preventatives are ideal for all breeds of dogs—please discuss this with your veterinarian when considering treatment options.

If the test is positive for heartworms this does not always mean disaster—it means that there are likely adult heartworms in your animal’s heart. Treating for an established infection requires sophisticated therapy, which should include 24-hour monitoring. To rid your animal of adult heartworms is often expensive and sometimes fatal to your animal. For these reasons, preventative therapy is very strongly recommended by the American Heartworm Society and veterinarians.

In general, veterinarians as a profession are becoming more and more informed about the presence of the disease and the dangers to your animals. Consequently, we are often recommending heartworm prevention to be given monthly, all year long. Often the heartworm preventatives have flea control as well, which is another one of our serious parasite problems on the coast.