5. Address the envelope. In the lower right third of the envelope, write the name of the person you are sending the letter to. Write the company name on the line below that (if there is a company name).
Once inside a new host, it takes approximately 6 months for the larvae to mature into adult heartworms. Once mature, heartworms can live for 5 to 7 years in dogs and up to 2 or 3 years in cats. Because of the longevity of these worms, each mosquito season can lead to an increasing number of worms in an infected pet.
Typically, you should begin heartworm treatment in puppies around 6 to 8 weeks of age, although some heartworm preventatives are suitable for even younger dogs. Once a dog reaches 6 months of age, however, you should not begin a preventative cycle without first having your dog tested for infection.