PSA- Mosquitos are crazy right now. Heartworm larvae are transmitted by infected mosquitoes. When the infected mosquito bites, the larvae pass through the tissue into the bloodstream. 47-67 days later they reach the arteries of the lungs where they continue to develop and grow. Once they arrive in the lungs, at three months post-infection, they can start to do damage leading to death.
Make sure your dogs are current on their heartworm medication, if not have them tested and then get and stay on it asap!