Heartworm Life Cycles

April is Heartworm Awareness Month, so it's only fitting that we provide you with a little insight into the life of the heartworm. Heartworms start life as microfilariae (also known as L1 or baby heartworms). Mosquitoes pick up the microfilariae when they ingest blood from an infected animal. Inside the mosquito, the larvae molt twice until they are at the L3 stage. Upon puncturing the skin of an animal, the L3 migrate from the mosquito's mouth parts into the puncture wound. From there, they migrate through the animal's body with the goal of maturing at the heart. In the right host, the adult heartworms reproduce, and the female heartworms release microfilariae in the bloodstream.
Everyone (or at least everyone around here) knows that dogs are pretty susceptible to heartworms, but did you know that cats can get heartworms too?Heartworms are adapted to live in a dog but not so much in a cat. In cats, heartworms are usually unable to develop in the numbers necessary to successfully reproduce (they often have single sex infections or don't produce reproduce to a level that is detectable). Also, while heartworms primarily reside in a dog's heart, heartworms in a cat primarily live in the lungs. 
We've posted some life cycles below so you can compare.