is transmitted by mosquitoes, and can be found in most areas of the country. When a mosquito bites an infected animal, the heartworm larvae are ingested along with the blood. Larvae mature to the infective stage within the body of the mosquito, then are transmitted to a dog or cat through a subsequent mosquito bite. Once inside the host animal, heartworms travel to the lungs and the right side of the heart, where they can grow and mate for several years. Adult heartworms reside in the pulmonary arteries, or right heart if large amount of worms are present and can grow to a length of 5-12 inches in dogs and 5-8 inches in cats.