Heartworm (Dirofilaria immitis) is a fairly large worm - up to 14 inches long - that, in adulthood, lives in the heart and pulmonary arteries of an infected dog. Dogs acquire this infection through mosquito bites as mosquitoes readily pick up larval heartworms from infected dogs and carry them to new dogs.
Adult heartworms live in the heart and pulmonary arteries, clogging up the circulation and causing inflammation. Heartworm disease can cause the following symptoms:
- Persistent cough
- Distended abdomen
- Reluctance to exercise
- Weight loss
Young heartworms spend several months maturing under the skin of the new dog and it is this period where they are vulnerable to heartworm preventive medications. If the young heartworm gets too old, the preventive medications will not reliably kill it.
It takes five to seven months for the young heartworm to become detectable by blood test.
Heartworm preventive medications are used to periodically kill larval heartworms that have managed to gain access to the dog’s body. At this point, the products available are intended for monthly use, with the exception of Proheart6 which is a biannual injection. This means each time they are given they kill all the heartworm larvae that have accumulated in the past month.
Our veterinarians recommend administering heartworm prevention once monthly year round!