A global genome study has revealed that canine heartworm may have an older and more complex evolutionary history than previously thought. Researchers led by the University of Sydney examined over 100 heartworm genomes from dogs and wild canids across four continents, challenging the idea that the parasite mainly spread through recent human movement of domestic dogs.

The findings suggest ancient canid species, including wolves and dingoes, played a key role in shaping regional heartworm populations over tens of thousands of years. The research, published in Communications Biology, used whole‑genome sequencing to track how parasite lineages diverged, revealing distinct populations formed by historic shifts in climate and animal movement.

In Australia, genetic signatures point to a possible link between local heartworms and parasites from Asia, raising the possibility that the disease arrived with the continent’s earliest dingoes. However, the authors caution that limited sample sizes mean a more recent introduction following European colonization cannot be ruled out.

Researchers say the work overturns long-held assumptions in parasitology and may help improve responses to emerging drug resistance. They note that further sampling from underrepresented regions will be needed to refine timelines and test competing origin theories.

“What we can say with confidence,” said professor Jan Slapeta, senior author of the University of Sydney School of Veterinary Science, “is that heartworm evolution is far older and more complex than a simple story of parasites hitchhiking with modern dogs.”