How are heartworms transmitted from one dog to another? They are mosquito-borne, when mosquitos feed on the dog. You see, when a mosquito bites a carrier they then take some microfilariae found in the carrier’s blood. Once in the mosquito, the microfilariae develop into infectious larvae. Once in the mosquito, the larvae become infectious within about fourteen days, when the exterior temperature is around 21 ˚C. If it is colder, the process can take a little longer.
As it becomes infectious, larvae can infect other dogs that the mosquito bites. As a matter of fact, when the mosquito feeds on blood, larvae migrate toward the dog and enter through the puncture hole, which is the first step of several months of travelling to reach the dog’s lungs. Six to seven months later, the larvae will reach the dog’s heart. Once it gets there, it becomes an adult that can reproduce, and a new cycle begins. If your neighbour’s dog is a carrier, they are a possible infectious source for all dogs in the area.