Here’s another reason to cook your meat and watch out for cat litter: The parasite Toxoplasma gondii, which breeds in cats and most often spreads to humans through raw meat, may increase the risk of brain cancer in humans, suggests a new study.
The researchers found a link between the presence of T. gondii antibodies in people’s blood, indicating previous exposure to the parasite, and the development of glioma, the most common type of Brain cancer, several years later.
The results, published Monday (January 11) in the International Journal of Cancer, “suggest that individuals with greater exposure to T. gondii the parasite is more likely to develop glioma, “says study co-author Anna Coghill, a cancer epidemiologist at the Moffitt Cancer Center in Tampa, Florida, said in a statement. However, Coghill cautioned that the current findings “need to be replicated in a larger and more diverse group of individuals” and that the overall risk of developing glioma in an average person remains low.
In addition, the current study cannot prove a cause and effect relationship. “It does not mean that T. gondii definitely causes glioma in all situations, “study co-author James Hodge, an epidemiologist at the American Cancer Society in Atlanta, said in the statement.” Some people with glioma do not have T. gondii antibodies and vice versa. ”
Related: 7 strange facts about the ‘mind control’ parasite Toxoplasma gondii
Cerebral parasite
T. gondii infects most warm-blooded animals, including humans. However, it undergoes sexual replication only in cats, so it must infect them to complete its life cycle. The parasite, which can infect the brain, is known to making infected rodents less cautious with cats and facilitating their own reproduction. It has also been linked to risky behavior in humans. Although humans can be exposed to the parasite by removing cat litter from an infected animal, a more common route of exposure is through eating raw or undercooked meat from an infected animal.
T. gondii infections, known as toxoplasmosis, are common, affecting about 2 billion people worldwide and 40 million in the United States, Live Science previously reported. Most people with the infection have no symptoms because their immune system keeps the parasite in check, but in rare cases, the parasite can cause severe symptoms, including loss of vision, according to Centers for Disease Control and Prevention (CDC).
Glioma is a deadly cancer, and glioblastoma is its most deadly subtype. The estimated five-year survival rate of glioblastoma is only 6% in people aged 55 and over, compared to the general population who do not have cancer, according to the American Cancer Society. Risk factors for glioma include being male, non-Hispanic white, older and taller.
To examine the influence of T. gondii exposure to the risk of developing glioma, the researchers looked for antibodies to T. gondii in blood samples from people with glioma (the samples were collected several years before diagnosis), as well as in a control group without cancer. The researchers used blood samples and data from participants in two previous studies: the Cancer Prevention Study-II of the American Cancer Society’s Nutrition Cohort (CPSII-NC) and the Janus Serum Bank of the Norwegian Cancer Registry (Janus).
Glioma participants were more likely than participants in the control group to have antibodies to T. gondii in their blood samples, the researchers found. In addition, in the Janus study participants, the risk of glioblastoma increased with T. gondii Antibody levels, which means that the higher your antibody levels, the greater the risk, the researchers found. However, the association between T. gondii glioma exposure and risk were not statistically significant for each individual antibody tested and each glioma subtype.
This was the first prospective study – that is, one that examined T. gondii exposure before cancer diagnosis – to report an association between T. gondii exposure and development of glioma, the authors wrote. The design of this study allowed researchers to avoid the possibility that a glioma-parasite link was actually due to gliomas, increasing the risk of infection by the parasite.
The identification of T. gondii as a risk factor for glioma may have practical implications. While most risk factors for glioma are not modifiable, exposure to the parasite is something that people can try to avoid, the authors note.
If other studies confirm these findings, “reducing exposure to this common food pathogen would offer the first tangible opportunity for the prevention of this highly aggressive brain tumor,” they concluded.
Geoff Hide, a parasitologist at Salford University in the United Kingdom, agrees that “in principle, reducing T. gondii exposure will likely prevent some gliomas – probably because the immune system is less stressed. “Hide was not involved in the current study, but he co-authored a 2019 study in the journal ERJ Open Research reporting a link between the presence of T. gondii antibodies and lung cancer.
“This study suggests an association between exposure to Toxoplasma gondii and increased risk of glioma, “Dr. Craig Horbinski, a neuropathologist at the Feinberg School of Medicine at Northwestern University in Chicago, told Live Science via email.” If the connection is real, preventing such exposure can reduce the risk of developing these symptoms, usually lethal cancers. “
But both Horbinski, who was not involved in the research, and the study authors believe that more data is needed to determine whether the association between exposure to the parasite and the development of glioma is true. “The data is interesting, but it is not enough to draw firm conclusions,” said Horbinski.
In the future, researchers should do more studies in larger populations, including more cases of glioma, said Horbinski. “This is the only way to resolve this controversy,” he added.
Originally published on Live Science.