On the Horizon: Canine Heartworm Vaccines

Canine heartworm infections have hovered around 1 million per year since the early 2000s, according to the AHS Heartworm Incidence Survey, and veterinarians cite noncompliance among pet owners as one of the top reasons for this. And yet, sustained use of heartworm prophylactics can lead to drug resistance. That’s why researchers in the U.K. are studying Dirofilaria immitis, the parasitic filarial worm that causes heartworm disease in dogs, in hopes of developing a canine heartworm vaccine.

“Currently, there are very few options for the sustainable prevention of heartworm disease in the likely event that drug resistance continues to spread,” says Ben Makepeace, Ph.D., of the University of Liverpool. “If we don’t find an alternative, then treating established adult worms will be very difficult in dogs.”

Makepeace is the principal investigator on the research, which is being funded by the Morris Animal Foundation and the American Heartworm Society. The research is aimed at exploring how key proteins produced by the worm might be useful in developing a canine heartworm vaccine.

Previously, Makepeace and his research team explored “how filarial parasites similar to ;D. immitis avoid destruction by producing a protein that blocks a key pathway alerting immune systems to their presence.” They also identified a second protein that prevents a dog’s T-cells from attacking the filarial parasites. These proteins render the host dog’s immune system powerless against the worms, allowing them to proliferate.

In the current study, Makepeace and other researchers seek to confirm their theory that the same proteins produced by D. immitis have a similar effect in dogs. They then plan to test different surface proteins to see which ones stimulate a dog’s immune system.

If successful, the team’s work could lay the groundwork for canine heartworm vaccine development—and eventually be applied to cats as well.

“An eventual heartworm vaccine would be highly beneficial for canine health as current preventive methods can be costly and rely on owner compliance,” says Janet Patterson-Kane, Ph.D., Morris Animal Foundation’s chief scientific officer. “A vaccine would also address the growing problem of drug resistance, which is of great concern to both pet owners and veterinarians.”