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.
Heartworm Life Cycle. When a mosquito bites a dog infected with heartworms, the mosquito ingests microfilariae, or heartworm larvae. The microfilariae migrate from the mosquito's digestive tract to its abdomen. After two to three weeks of growth there, the microfilariae become infective.