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Heartworm Life Cycle

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Heartworm Life Cycle

Heartworm Life Cycle


  1. A mosquito bites an infected dog and ingests tiny heartworm larvae along with the animal’s blood. Other carriers of heartworm disease include wolves, foxes, ferrets, coyotes and raccoons.
  2. Inside the mosquito, these larvae develop into their infective stage.
  3. When the same mosquito bites another dog, the larvae infect the healthy animal.
  4. Without a monthly dose of preventive, the larvae continue to develop inside the dog, eventually reaching the heart and lungs.
  5. One million dogs are estimated to be heartworm positive in the United States each year.1

Important Safety Information:
HEARTGARD (ivermectin) is well tolerated. All dogs should be tested for heartworm infection before starting a preventive program. Following the use of HEARTGARD, digestive and neurological side effects have rarely been reported. For more information, please visit

Click here to download full prescribing information.
1Line S. Vet’s advice: Beware the rising risk of heartworms in dogs. Available at Accessed October 11, 2010.

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