They found evidence that people infected with Toxoplasma gondii, or T. gondii, are at an increased risk of developing rare but highly fatal gliomas.
The parasite can sometimes form cysts in the brain and the inflammation associated with these cysts may be responsible, the researchers reported in the International Journal of Cancer.
A team of researchers led by epidemiologist James Hodge, from the population science department of the American Cancer Society, and Anna Coghill, from the cancer epidemiology department at the H. Lee Moffit Cancer Center and Florida Research Institute, analyzed the association between antibodies to T gondii in blood samples and the risk of glioma in two groups of people.
“In both cohorts, we observed a positive association suggestive between seropositivity for T. gondii antibodies and the risk of glioma,” wrote the researchers. The associations of glioma were strongest for people who had higher levels of antibodies against T. gondii.
T. gondii is a common parasite that most infects people through contaminated food or water from raw or undercooked meat from infected animals. Twenty percent to 50% of the global population has already been exposed to the parasite, according to the study.
Gliomas make up the majority – 80% – of malignant brain tumors. Glioblastomas are the most common subtype. Glioblastomas have a relative five-year survival rate of just 5%.
“Our findings provide the first prospective evidence of an association between T. gondii infection and the risk of glioma, results that should be confirmed in independent studies,” wrote the researchers.
“This does not mean that T. gondii definitely causes glioma in all situations. Some people with glioma do not have antibodies against T. gondii and vice versa,” said Hodge in a statement.
“The findings suggest that individuals with greater exposure to the T. gondii parasite are more likely to develop glioma,” added Coghill. “However, it should be noted that the absolute risk of being diagnosed with a glioma remains low, and these findings need to be replicated in a larger and more diverse group of individuals.”
If the study’s findings are replicated, “reducing exposure to this common food pathogen would offer the first tangible opportunity to prevent this highly aggressive brain tumor,” the researchers said.
CNN’s Katie Hunt contributed to this report.