How is heartworm disease transmitted?
Heartworms have been found in a variety of wild and domestic animals. Mosquitos carry immature froms of the heartworm from an infected animal to a new host by taking a blood meal from both animals. As the mosquito feeds from the first animal, usually a dog, it picks up the microfilariae (the offspring of adult heartworms) as it engorges with blood. These microfilariae mature in the mosquito, developing into the infective form, the larval stae of D. immitis. When the mosquito subsequently bites another animal, the larvae are introduced to the new host through the bite wound. The larvae eventually make their way to the heart and associated blood vessels by migrating through the body. Inside the heart they mature and begin producing microfilariae, completing the lifecycle. These new microfilariae are then ready to be passed on to another dog or cat.
Heartworms are transmitted by mosquitoes. Adult female heartworms release microfilariae into the bloodstream of infected animals. When a mosquito bites an infected animal, it takes up blood containing these microfilariae. The microfilariae incubate in the mosquito for 10 to 14 days, during which time they become infective larvae. When the mosquito bites another animal, the infective larvae are passed on to the second animal through the wound. Infective larvae migrate through the tissues of the body for two to three months, and then enter the heart and pulmonary arteries, where they reach adult size in another three months. If both sexes are present, the mature worms will mate and produce new microfilariae, and the cycle begins again. Adult heartworms may survive for five to seven years in dogs. The mosquito is the only natural agent of transmission for heartworms. Microfilariae cannot mature into adult heartworms without passing through a mosquito.
