Toxoplasmosis, one of the most prevalent parasitic diseases in the world, produces no obvious symptoms in humans. However, a new study published in the journal Evolutionary Psychology has found the disease “can spur changes in a person’s political beliefs and values” through an inflammatory reaction.

“Toxoplasma is a very widespread parasite, and therefore its prevalence (which varies dramatically between and within countries) can influence not only the political climate in different countries and different social strata of the population, but also real-world politics and, consequently, history,” said Jaroslav Flegr, a professor at Charles University, Prague and an author of the recent study.

Around 30% of the human population in both developed and developing countries is considered to be infected with long-term toxoplasmosis. With several reports pointing to the rise in conservatism and authoritarianism worldwide, this new study paves the way to understanding how biological factors could underpin complex political worldviews. More specifically, Toxoplasma could make some individuals lean conservative by dialling up their disposition toward tribalism.

This is not the first study to speak of Toxoplasma’s effects on personality and behavioral changes. In a 2016 paper, researchers linked toxoplasmosis to an individual’s sexual interests. The study found, “Toxoplasma-infected individuals expressed higher attraction to nonconventional sexual practices” such as “bondage, violence, zoophilia, and fetishism.”

Here’s what we known about the parasite’s impact on our health—behavior notwithstanding. Toxoplasmosis is caused by a common parasite Toxoplasma gondii. Several commonplace situations could expose humans to this parasite, including eating uncooked or contaminated meat, drinking unpasteurized milk or cleaning the litter box of an infected cat. Toxoplasma is known to only reproduce sexually in cats. The presence of Toxoplasma eggs in cat feces makes this the most common cause of infection, but also one that could be counteracted by veterinary vaccines.

While previous studies have termed it a “relatively harmless infection”, concerns have been raised regarding the danger it poses to people with compromised immune systems and pregnant women. Researchers also stated that this parasite could increase a person’s risk of contracting diseases and developing disorders, including ischemic heart disease, certain cancers, and epilepsy.

The authors of the present study have attributed the parasite’s effects on emotional and behavioral processes to an activation of the immune system. Their research over the years showed how Toxoplasma negatively impacts people’s physical and mental health. A 2015 study published in the journal Brain, Behavior, and Immunity, also suggested that a toxoplasmosis infection is “strongly and significantly associated with GAD” or generalized anxiety disorder. Those with more severe infection were three times more likely to have developed generalized anxiety.

This happens due to an increase insome proinflammatory cytokines—small proteins that help cells communicate during an immune response. The resulting inflammation could lead to changes in personality traits, which, researchers now suggest, may affect one’s political views as well.

The recent study analyzed 2,315 Czech residents to investigate the links between the disease and their political belief systems. Participants were asked questions about their mental and physical health and their political values, assessing them based on four factors: Tribalism, Cultural Liberalism, Anti-authoritarianism, and Economic Equity.

People infected with toxoplasmosis showed lower conscientiousness, generosity and novelty-seeking. Their findings also associated the infection with higher Tribalism, where loyalty to one’s tribe takes precedence. In a political context, these tribes can be defined on the basis of several factors, including race, caste, color and nationality. By drawing boundaries that separates “us” from “them”, tribalism perpetuates an ‘otherization’ of communities and groups whether on social, economic or political grounds.

In a 2019 report in The Conversation, Arash Javanbakht—an Assistant Professor of Psychiatry at Wayne State University—explained, “Tribalism is the biological loophole that many politicians have banked on for a long time: tapping into our fears and tribal instincts. Some examples are Nazism, the Ku Klux Klan, religious wars and the Dark Ages. The typical pattern is to give the other humans a different label than us, and say they are going to harm us or our resources, and to turn the other group into a concept.”

Javanbhakt further wrote: “At a tribal level, people are more emotional and consequently less logical.” A Toxoplasma infection was also associated with lower Cultural Liberalism and lower Anti-authoritarianism.

Related on The Swaddle:

How a ‘Mind‑Altering’ Parasite Makes People Seem More Sexually Appealing

While an overall sample analysis revealed an association with higher Tribalism, when the researchers analyzed the findings separately for men and women respondents, significant gender differences came to light. They found that toxoplasmosis was not associated with Tribalism in men, something the researchers attributed to a smaller sample size of male participants. Meanwhile, infected women scored higher in Tribalism and lower in Cultural Liberalism.

Further, the infection in men was positively linked with Economic Equity or the idea of a fair and equitable society. The authors of the study noted this to be a surprising development, as infected men had previously been associated with “higher risk-taking behavior and higher entrepreneurship activity.” The smaller ratio of men to women participants is a limitation of the study and a possible reflection of the fact that women are more likely to know whether they have contracted the infection due to testing during pregnancy. The authors of the study highlighted the need for further investigation, keeping gender differences in mind. Another limitation, moreover, is that the study’s participants also hail from a small region with low parasitic stress.

The effects of a parasitic infection in shaping political attitudes may be surprising, yet the authors said these findings align with past research that shows “people from areas particularly affected by parasites demonstrate higher conservatism and authoritarianism.”

Worldover, we are witnessing a rise in political conservatism. The Global State of Democracy Report, 2021 highlighted how a higher number of countries moved towards authoritarianism in 2020. “Democratically elected Governments, including established democracies, are increasingly adopting authoritarian tactics. This democratic backsliding has often enjoyed significant popular support,” the report stated. Among the most “worrying examples of backsliding” were India and Brazil. Freedom House’s Freedom in the World 2021 report also indicated the “expansion of authoritarian rule”, marking the “15th consecutive year of decline in global freedom.”

The latest research on the effects of toxoplasmosis reveals the possible role of biological factors in inducing personality changes that, in turn, shape political climates. Coupled with its studied effects on stress, mental health and physical well-being as well as its correlation with specific disease burden, this parasitic infection also becomes a “global health hazard”—one that prompts the need “to find a Toxoplasma vaccine and a method of treatment for lifelong latent toxoplasmosis.”

While one might expect the world’s political turmoil to be sociological in nature, then, a common parasite emerges as a new factor to contend with.