Could a brain parasite found in cats help soccer teams win at the World Cup?

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July 1 2010 7:26 PM

Landon Donovan Needs a Cat

Could a brain parasite found in cats help soccer teams win at the World Cup?

Ghana player Kevin-Prince Boateng. Click image to expand.
Ghana player Kevin-Prince Boateng

What if I told you that last week I predicted all eight winners of a round of the World Cup? And that instead of rankings or divination all I did was look up how many people in each team's home country had a tiny parasite lurking in their amygdalas? Would you believe me? A decade ago, Discover Magazine concluded that parasites ruled the world, and now I'm going to try to tell you that, at the very least, parasites rule the World Cup.

First, a quick primer on the organism in question, a single-celled parasite called Toxoplasma gondii.

Toxo is one of the most successful parasites in the world and is found in almost every type of mammal. Goats, cows, pigs, sheep, humans. But it spends its time trying to get into the stomach of a cat, the only place where it can successfully reproduce. Thus the organism has evolved an unusual lifecycle relating to the brains of rats and mice. Rodents ingest little bits of Toxo from cat feces and Toxo goes straight to their heads.Once there, it scrambles the neurons around and reverses the animals' natural aversion to cat urine. Soon after, a recently relieved cat returns to the scene and takes its supper. In other words, the rat plays taxi to the parasite, finding it a new feline host and completing the Toxo lifecycle.

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Livestock fields are full of fertilizer made from, you guessed it, bits of cat feces. When the cows and goats graze, they ingest Toxo, and it sneaks its way into their brains. Eat one of these livestock uncooked and you'll get Toxo in your brain, too. Thanks to the urbanization of cats (and their feces), almost a third of the human population now has a chronic, latent, and seemingly innocuous Toxo infection. This is, of course, an average: Rates vary a great deal from one country to another, from 6 percent in South Korea to 92 percent in Ghana.

A recent article in The Economist pushed the idea that Toxo infection can subtly influence human behavior and, writ large, worldwide culture. Studies find that national infection rates correlate with overall personality traits like neuroticism, perhaps because Toxo is having some effect on how our brains function. (According to one theory, the parasite can alter levels of dopamine, a neurotransmitter associated with reward and motivation.) But this research fails to consider one of the most compelling measures of national character: World Cup victories. Could rates of Toxo infection predict soccer success?

If we set aside the qualifying rounds (in which teams can play to a draw) and focus on matches with a clear winner, the results are very compelling. In the knockout round of this year's tournament, eight out of eight winners so far have been the teams whose countries had higher rates of Toxo infection. If we go back to the 2006 World Cup, seven out of eight knockout-round winners could be predicted by higher Toxo rates. The one exception to the rule was Brazil's defeat of Ghana, a match between two nations that each have very high rates. (Aside from having the winningest team in World Cup history, Brazil has quite a few cases of Toxo: Two out of three Brazilians are infected.)

It gets better. Rank the top 25 FIFA team countries by Toxo rate and you get, in order from the top: Brazil (67 percent), Argentina (52 percent), France (45 percent), Spain (44 percent), and Germany (43 percent). Collectively, these are the teams responsible for eight of the last 10 World Cup overall winners. Spain, the only one of the group never to have won a cup, is no subpar outlier—the Spaniards have the most World Cup victories of any perpetual runner-up. 

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