Can your cat's parasites help you succeed?
A paper out this week claims that the parasite Toxoplasma gondii, which cats shed in their faeces, can - if we catch it - reduce our fear of failure and boost our chances of success! According to a team from Colorado, professionals at business events were nearly twice as likely to have started their own company if they tested positive for toxo. So are parasites really pulling the strings? Chris Smith was joined by Cambridge University’s Jim Ajioka, who wasn’t involved in the study, but does work on Toxoplasma....
Jim - Basically what they did is they surveyed a number of business students and other businessmen in various places in the US and in Europe and just simply asked the question does your exposure to Toxoplasma correlate with your ability to do business in an enrtrepreneurial way, or at least in a survey they could point that out, and they found a correlation.
Chris - There’s emphasis on the fact that they found a correlation. They’re not saying that being infected with toxoplasmosis causes you to become very good at business?
Jim - No, that’s right.
Chris - Because if that were true, populations like France where the majority of the population, as far as I know, it’s at least half the population carry it isn’t it? They ought to be leading the world.
Jim - Yeah, that’s right. All of these things are probably small effects but there’s been a number of studies, both in animals and in other survey studies in humans, where they’ve looked at changes in behaviour between when you’re exposed to toxoplasma or not, and most of those have shown some kind of correlation. In the animal studies there’s really good evidence that there is neurological disturbance with the parasite.
Chris - What does toxo actually do? What’s it’s life cycle, and how might this affect that the Colorado team have picked up be biologically plausible based on what we know about what the toxoplasma parasite does to our nervous system?
Jim - Right. So the parasite has two parts to its lifecycle that are important. One is the sexual part of the lifecycle where the cat is the definitive host, and the parasite will go into the cat and be shed in the faeces, as you’ve noted before, in probably about 10 million infectious particles.
Chris - So when the cat goes in its litter tray, each cat turd could infect 10 million people?
Jim - Across a couple of weeks, yeah, they’ll shed about 10 million. If you pick up one of those things; it’s on your vegetables or you’re a keen gardener you pick those up, you'll put them in your mouth, you’ll probably get toxoplasma, an infection but you won’t notice it because in humans the symptoms are actually quite mild. First you will establish an acute infection which you probably wouldn’t notice because it doesn’t really do much in humans. Other animals it does. And the parasite will be cleared by your immune system, but what it tries to do is to set up a resting form or chronic form in places where your immune system doesn’t work very well - your brain being one of those places. We know from animal studies that you will get neurodegeneration from the presence of the parasite in a chronic infection in the brain.
Chris - But what’s the sort of biological origin of the risk taking/daring/entrepreneurial flare that people might show if they have it? Where does that come from?
Jim - The idea is that the parasite it’s job really is to replicate and then spread - that’s what natural selection would do. And so part of the way that it spreads is to be eaten by other animals. If you are more risk taking and your behaviour for trying to avoid predation is lower and so natural selection will select the parasite to manipulate the host so that it will be more easily eaten.
Chris - You said that the definitive host where the parasite wants to be is a cat therefore is it mice and rats that cats classically traditionally catch that tend to have the more daring behaviour normally when they’re infected with toxin?
Jim - That’s right. When you look at other studies: Joanne Webster at Oxford for example did some nice studies with rats and, in fact, she showed that rats had definitely had a much more risk taking behaviour with regards to predator presence than the ones that were not infected.