The Voice Within May Be Toxoplasma Speaking

Toxoplasma gondii, a parasite that reproduces in cats and can infect humans, is known to alter behavior. A recent study shows that infected humans tend to be more entrepreneurial.

AsianScientist (Jul. 31, 2018) – As one of Earth’s most cerebral creatures, humans like to think that we are in the driver’s seat when it comes to decision making. We weigh up the risks and rewards of our actions, spend some time thinking about the possible consequences, then decide whether or not to follow through with those actions. It’s all very logic-driven, right?

But recent research has increasingly shown that what we perceive as rational thought could actually be the subtle promptings of microorganisms that have taken up residence in our bodies. From commensal bacteria to subversive parasites, our tiny ‘pillion riders’ may be the shoulder angels/devils whispering in our ears to steer us in directions befitting their goals instead of ours.


The cat’s meow

For me, one of the most fascinating of ‘mind control’ microbes is Toxoplasma gondii, a parasite that infects a staggering array of warm-blooded animals—including humans. Rodents infected with T. gondii become attracted to cats, often resulting in their demise when they are caught and eaten. This allows the parasite to complete its life cycle in the cat’s gut where it reproduces sexually. Cats then shed the parasite in their feces, and the cycle continues. Having owned a cat for more than 17 years, I’ve always wondered if my attraction to my pet feline is my own, or parasite-induced.

Thankfully, in humans, infection by T. gondii—or toxoplasmosis—is generally asymptomatic. Most people don’t even know they are infected and recover without ever needing treatment. In immune compromised individuals, however, the parasite has been known to cause eye complications and encephalitis—inflammation of the brain. Toxoplasmosis in pregnant women, especially during the early stages of gestation, can also be a cause for concern because the parasite can affect fetal development and impair vision in newborns.

But what about T. gondii-induced behavioral changes in humans? Studies have shown that compared to healthy individuals, infected men and women exhibit reduced novelty-seeking behavior, as well as heightened extraversion and less conscientiousness. Links between toxoplasmosis and schizophrenia have surfaced, and one study even showed that infected subjects had a 2.65 times higher risk of traffic accidents than their uninfected counterparts.

If all of this is beginning to sound rather alarming and you’re considering abandoning your cat, hold that thought. There is a possible upside of toxoplasmosis, and it is found in the realm of business and entrepreneurship.


The parasitic entrepreneur

When researchers at the University of Colorado Boulder, US, sampled the saliva of 1,495 students for an immune protein indicative of T. gondii infection, they found that those who tested positive for the protein were 1.4 times more likely to major in business than those who tested negative. Infected students were also 1.7 times more likely to gravitate towards management and entrepreneurship.

Next, going beyond the university, the researchers obtained saliva samples from professionals at entrepreneurship events. Their analysis of these samples revealed that T. gondii-infected individuals were almost twice as likely to have started their own businesses than uninfected ‘controls.’ This aligned with the researchers’ findings of heightened entrepreneurial inclinations in infected students on campus.

Having identified a link between toxoplasmosis and entrepreneurship behavior at the individual level, the researchers then sought to verify whether the correlation was also observable at the global scale. Tapping on country-level databases of T. gondii infection over the past quarter-century, they reported that “infection prevalence was a consistent, positive predictor of entrepreneurial activity and intentions.” They also highlighted that the fear of failure was weaker in nations reporting higher rates of infection.

An uncanny similarity between T. gondii-infected mice and men thus surfaces. It would seem that failure is to humans what cats are to mice—an object of paralyzing fear, a terror that T. gondii seems to be able to soothe away. A common biological mechanism must be at play here, and some studies attribute the behavioral changes brought on by toxoplasmosis to disruption of the dopamine system in the brain—the system that regulates sensations of pleasure.

Regardless of the precise mechanism, it’s clear that some of our most basic instincts and impulses can be shaped and hijacked by the microscopic creatures that share our environment. So the next time you feel a craving, or a desire to be reckless, ask yourself if it’s really you in control, or whether you’re just bending to the will of something that lives inside of you.


This article is from a monthly column called Hacking a PhD. Click here to see the other articles in this series.

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Copyright: Asian Scientist Magazine; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Jeremy received his PhD from Nanyang Technological University, Singapore, where he studied the role of the tumor microenvironment in cancer progression. He believes that behind each scientific discovery is a fascinating story waiting to be told, and he hopes to tell these stories as a digital editor at Asian Scientist Magazine.

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