Are you prone to bouts of aggressive road rage? Do your friends label you a "crazy cat person"? Well, the two characteristics might be more linked than you think.
It turns out that a parasite commonly carried by cats, Toxoplasma gondii, can cause psychiatric disorders in humans, including episodes of explosive rage, reports New Scientist.
Cats are such popular pets worldwide that an estimated 1 in 3 people may carry the parasite, possibly altering human behavior on a large scale for the worst.
The parasite T. gondii probably doesn't want to infect humans. Its intended targets are rodents. When a mouse or rat is infected, the pathogen is capable of spreading into the animal's brain tissue, where it can manipulate behavior to make the rodents less fearful of cats. This increased boldness around cats makes the rodents more likely to get eaten, of course, thus allowing the parasite to pass to the cats, wherein it can complete its lifecycle.
But T. gondii can also survive within other hosts too, humans included. It is transmitted after exposure to cat feces (think: litter boxes, or getting cut by a cat's claws after the cat has spent some time digging around in a litter box). And like it does in rats and mice, the parasite moves into human brains too. The question is, can it influence human behavior like it does rodent behavior?
There's increasing evidence that it does. For instance, there's some speculation that cat obsessions, exhibited by people often labeled as "crazy cat people," might be one possible effect of infection. (The pathogen might even help explain the prevalence of viral cat videos found online.) Infection has also loosely been linked to conditions like schizophrenia, bipolar disorder and suicidal behavior.
Now researchers have also linked T. gondii to explosive road rage-like bouts of anger, a psychiatric condition known as intermittent explosive disorder, or IED. To make matters worse, people infected with T. gondii also have slower reaction times and are more likely to be involved in car accidents.
Emil Coccaro at the University of Chicago and his colleagues examined 358 adults who fell into one of three groups: people with IED, people with other psychiatric conditions, and controls who had not been diagnosed with any psychiatric condition. Sure enough, people with IED were twice as likely to test positive for T. gondii compared to the control group.
“The findings make sense,” explained Paul Ewald, an evolutionary biologist at the University of Louisville in Kentucky. “A mouse that is preoccupied with attacks on another mouse may be easy prey for a cat.”
Of course, it's also possible that T. gondii's effects on humans are simply an unintended consequence, the result of a parasite that has found its way into an unexpected host.
More research will need to be done to understand exactly how the parasite reacts within a human host before an adequate cure can be found. Finding a cure may still not be forthcoming, however.
“These parasites are so bloody difficult to kill,” said Coccaro.
In the meantime, if you're a crazy cat person, perhaps it's better to let someone else take the wheel when your temper is being tested.