Your cat litter may contain a special little bug that holds the key to a new form of cancer treatment. Scientists have pinpointed a particular parasite that stimulates the immune system to attack tumors, and this single-celled parasite is often found in cats.

Toxoplasma gondii (T. gondii) frequently thrives in cats’ intestines, but is capable of living in any mammal, including humans. It affects about one-third of the human population, 60 million of which are living in the U.S. A human living with T. gondii in their system will typically experience an intense immune response, akin to that of a body fighting cancerous cells, which is what prompted scientists to begin looking into it.

“We know biologically this parasite has figured out how to stimulate the exact immune responses you want to fight cancer,” David J. Bzik, a professor of Microbiology and Immunology at the Geisel School of Medicine at Dartmouth, said in a press release. The body fights T. gondii by producing natural killer cells as well as cytotoxic T cells, which can also battle cancer. The researchers found that inserting T. gondii into a cancer patient’s body could jumpstart the immune system that is often impaired by cancer itself.

“The biology of this organism is inherently different from other microbe-based immunotherapeutic strategies that typically just tickle immune cells from the outside,” Barbara Fox, senior research associate of Microbiology and Immunology, said in the press release. “By gaining preferential access to the inside of powerful innate immune cell types, our mutated strain of T. gondii reprograms the natural power of the immune system to clear tumor cells and cancer.”

In their study, the researchers discovered a way to inject patients with a certain immunotherapeutic vaccine known as “cps.” It wouldn’t be safe to inject people with living, replicating strains of T. gondii. Thus, the vaccine was able to deliver the parasite, without an ability for it to grow or replicate in people. “Aggressive cancers too often seem like fast moving train wrecks,” Bzik said in the press release. “Cps is the microscopic, but super strong, hero that catches the wayward trains, halts their progression, and shrinks them until they disappear.”

Cancer immunotherapy involves leveraging the immune system to fight the diseases, either by stimulating the immune system or by providing the system certain components and man-made proteins. Bzik believes that cps holds significant potential for treating cancer in the future, noting that the vaccine “stimulates amazingly effective immunotherapy against cancers, superior to anything seen before. The ability of cps to communicate in different and unique ways with the cancer and special cells of the immune system breaks the control that cancer has leveraged over the immune system.”