What is Heartworm?
Heartworm is a parasite which, as its name implies, lives in the heart and lung arteries. Adult heartworms, thin thread-like worms averaging 10 to 12 inches long, produce large numbers of microscopic offspring called microfilariae that they travel throughout the body in the bloodstream.
How is Heartworm Spread?
Canine and Feline Heartworm is transmitted solely by mosquitoes. When a mosquito bites an infected animal, it sucks out blood containing the microfilariae. After about two weeks in the mosquito, the microfilariae become infective larvae. When the mosquito then bites another animal, the infective larvae are transmitted. The two-week period during which the microfilariae become infective is necessary for the transmission of heartworm; therefore, this parasite cannot be spread from dog to dog.
** There is no unaffected area or season in the United States since mosquitoes are prevalent in all 50 states and winters are not cold enough for long enough to kill all the mosquitoes.
Symptoms of Heartworm
Unfortunately, clinical symptoms do not generally occur early in the disease. The pet may harbor the parasite for years before any symptoms develop. This first sign is a non-productive cough make worse by exercise and the pet tends to tire very quickly. Difficulty in breathing, fainting, listlessness, weight loss, and other signs of heart and lung disease will become more frequent as the disease progresses. Secondary liver and kidney disease are also relatively common occurrences in advanced heartworm disease in dogs.
Diagnosis of Heartworm Disease
A common blood screening test, Heartworm Serology, can verify the presence of adult heartworms which are producing microfilariae. Radiographs or x-rays are used to detected heartworm disease before microfilariae are produced.
Treatment and Prevention of Heartworm Disease
Different drugs are needed to eliminate the adult parasite and the microfilariae. Most dogs can be treated is the disease is caught early, although heartworm disease is fatal if it remains undetected. The best treatment is prevention. The once a month preventative, Revolution® or Heartgard® for dogs and Revolution® for cats, should be given year-round and lifelong. These drugs will also help prevent some intestinal parasites. Dogs should have bi-annual blood tests to ensure the absence of heartworm disease.