How Do Dogs and Cats Get Heartworm Disease?

Once the larvae pass through the dog’s skin under the mosquito bite, they grow for up to two weeks under the tissue. After they have developed to the next larval stage, they move to the dog’s chest and abdomen muscles until they molt once again, up to two months after the initial bite. Finally, the larvae enter the bloodstream and molt and grow as they travel to the heart and surrounding vessels. These mature heartworms have been in your dog’s system for up to four months.

If one pet has heartworm disease, it doesn’t mean your other pets will become infected with the parasite. Because heartworms can only be transmitted through an infected mosquito bite, dogs and cats that share a common space will not transmit the disease to each other. Even if a mosquito bites the infected pet and then an uninfected pet, the microfilia will not have enough time to incubate and pass along to its next host. Only a mosquito previously infected with incubated heartworm disease will be able to transmit it.