How do dogs contract heartworm?

It takes about seven months, once a dog is bitten by an infected mosquito, for the larvae to mature into adult heartworms. They then lodge in the heart, lungs, and surrounding blood vessels and begin reproducing. read more

Mosquitos contract heartworm microfilaria when they bite infected dogs. The microfilaria then undergo an incubation period inside the mosquito for up to two weeks. During this time, the infected mosquito cannot spread heartworm disease. read more

When a dog is first infested with heartworm there are no visible or detectable signs. In fact, even a blood test will not detect heartworms initially. The changes in dogs begin when during the final molt of the heartworm larvae; it is then that the immature L5 larvae arrive in the right ventricle and neighboring blood vessels. read more