Chapter Two
Chapter Two
The Heartworm Lifecycle
The life cycle of a heartworm begins when a female mosquito bites an infected dog and ingests the Dirofilaria microfilariae during a blood meal. A single dog can be bitten dozens of times by mosquitoes in a single 24 hour period (Capelli, 2013)5. It only takes one mosquito to transmit a heartworm infection from one dog to the next (AHS, 2016)3.
The microfilariae develop further for about 14-16 days in the mosquito’s gut and kidney organs and then enter its mouthparts. At this stage, they are infective L3 larvae and can complete their maturation to adulthood once they enter a dog.
Infective larvae enter the dog’s body when the mosquito bites the dog. They migrate through the animal’s tissues and then into the bloodstream and eventually find their way to the lungs and adjacent blood vessels where they mature to adults; mating and reproducing microfilariae within 6 – 7 months after the bite of the infected mosquito. The target host of interest to us is the dog or cat, but a wide variety of other animals can also be infected, including wild felids, mustelids, pinnipeds, beaver, horses, and humans.
3 https://www.heartwormsociety.org/ accessed October 16, 2016.
5 Capelli et al., Risk of canine and human exposure to Dirofilaria immitis infected mosquitoes
6 http://www.cdc.gov/parasites/dirofilariasis/biology_d_immitis.html