Heya right back.
First, other mammals can become infected/infested with heartworm. Specifically, in endemic areas cats can be a dead end host. Also, I believe there have been microfilaria from several related species found in humans in Africa.
Parasites tend to develop a pretty specific way of using their host. This usually entails the parasite evolving along with the host species. The complex interactions between host and parasite are the reasons why many parasites are host specific. That said, there are many parasites with looser ties to their host that infect many species.
Maybe a parasitologist will be along to give a better answer.