How Your Cat Is Making You Crazy
source: http://www.theatlantic.com/magazine/archive/2012/03/how-your-cat-is-making-you-crazy/308873/
Jaroslav Flegr is no kook. And yet, for years, he
suspected his mind had been taken over by parasites that had invaded his
brain. So the prolific biologist took his science-fiction hunch into
the lab. What he’s now discovering will startle you. Could tiny
organisms carried by
house cats be creeping into our brains,
causing everything from car wrecks to
schizophrenia?
inShare8 By
Kathleen McAuliffe
Michal Novotný
N
o one would accuse
Jaroslav Flegr of being a conformist. A self-described “sloppy
dresser,” the 53-year-old Czech scientist has the contemplative air of
someone habitually lost in thought, and his still-youthful, square-jawed
face is framed by frizzy red hair that encircles his head like a ring
of fire.
Certainly Flegr’s thinking is jarringly unconventional. Starting in
the early 1990s, he began to suspect that a single-celled parasite in
the protozoan family was subtly manipulating his personality, causing
him to behave in strange, often self-destructive ways. And if it was
messing with his mind, he reasoned, it was probably doing the same to
others.
The parasite, which is excreted by cats in their feces, is called
Toxoplasma gondii (
T. gondii or
Toxo
for short) and is the microbe that causes toxoplasmosis—the reason
pregnant women are told to avoid cats’ litter boxes. Since the 1920s,
doctors have recognized that a woman who becomes infected during
pregnancy can transmit the disease to the fetus, in some cases resulting
in severe brain damage or death.
T. gondii is also a major threat to people with weakened immunity: in the early days of the
AIDS
epidemic, before good antiretroviral drugs were developed, it was to
blame for the dementia that afflicted many patients at the disease’s end
stage. Healthy children and adults, however, usually experience nothing
worse than brief flu-like symptoms before quickly fighting off the
protozoan, which thereafter lies dormant inside brain cells—or at least
that’s the standard medical wisdom.
But if Flegr is right, the “latent” parasite may be quietly
tweaking the connections between our neurons, changing our response to
frightening situations, our trust in others, how outgoing we are, and
even our preference for certain scents. And that’s not all. He also
believes that the organism contributes to car crashes, suicides, and
mental disorders such as schizophrenia. When you add up all the
different ways it can harm us, says Flegr, “
Toxoplasma might even kill as many people as malaria, or at least a million people a year.”
An evolutionary biologist at Charles University in Prague, Flegr
has pursued this theory for decades in relative obscurity. Because he
struggles with English and is not much of a conversationalist even in
his native tongue, he rarely travels to scientific conferences. That
“may be one of the reasons my theory is not better known,” he says. And,
he believes, his views may invite deep-seated opposition. “There is
strong psychological resistance to the possibility that human behavior
can be influenced by some stupid parasite,” he says. “Nobody likes to
feel like a puppet. Reviewers [of my scientific papers] may have been
offended.” Another more obvious reason for resistance, of course, is
that Flegr’s notions sound an awful lot like fringe science, right up
there with UFO sightings and claims of dolphins telepathically
communicating with humans.
But after years of being ignored or discounted, Flegr is starting
to gain respectability. Psychedelic as his claims may sound, many
researchers, including such big names in neuroscience as Stanford’s
Robert Sapolsky, think he could well be onto something. Flegr’s “studies
are well conducted, and I can see no reason to doubt them,” Sapolsky
tells me. Indeed, recent findings from Sapolsky’s lab and British groups
suggest that the parasite is capable of extraordinary shenanigans.
T. gondii,
reports Sapolsky, can turn a rat’s strong innate aversion to cats into
an attraction, luring it into the jaws of its No. 1 predator. Even more
amazing is how it does this: the organism rewires circuits in parts of
the brain that deal with such primal emotions as fear, anxiety, and
sexual arousal. “Overall,” says Sapolsky, “this is wild, bizarre
neurobiology.” Another academic heavyweight who takes Flegr seriously is
the schizophrenia expert E. Fuller Torrey, director of the Stanley
Medical Research Institute, in Maryland. “I admire Jaroslav for doing
[this research],” he says. “It’s obviously not politically correct, in
the sense that not many labs are doing it. He’s done it mostly on his
own, with very little support. I think it bears looking at. I find it
completely credible.”
What’s more, many experts think
T. gondii may be far from
the only microscopic puppeteer capable of pulling our strings. “My guess
is that there are scads more examples of this going on in mammals, with
parasites we’ve never even heard of,” says Sapolsky.
Familiar to most of us, of course, is the rabies virus. On the
verge of killing a dog, bat, or other warm-blooded host, it stirs the
animal into a rage while simultaneously migrating from the nervous
system to the creature’s saliva, ensuring that when the host bites, the
virus will live on in a new carrier. But aside from rabies, stories of
parasites commandeering the behavior of large-brained mammals are rare.
The far more common victims of parasitic mind control—at least the ones
we know about—are fish, crustaceans, and legions of insects, according
to Janice Moore, a behavioral biologist at Colorado State University.
“Flies, ants, caterpillars, wasps, you name it—there are truckloads of
them behaving weirdly as a result of parasites,” she says.
Consider
Polysphincta gutfreundi, a parasitic wasp that
grabs hold of an orb spider and attaches a tiny egg to its belly. A
wormlike larva emerges from the egg, and then releases chemicals that
prompt the spider to abandon weaving its familiar spiral web and instead
spin its silk thread into a special pattern that will hold the cocoon
in which the larva matures. The “possessed” spider even crochets a
specific geometric design in the net, camouflaging the cocoon from the
wasp’s predators.
Flegr himself traces his life’s work to another master of mind
control. Almost 30 years ago, as he was reading a book by the British
evolutionary biologist Richard Dawkins, Flegr was captivated by a
passage describing how a flatworm turns an ant into its slave by
invading the ant’s nervous system. A drop in temperature normally causes
ants to head underground, but the infected insect instead climbs to the
top of a blade of grass and clamps down on it, becoming easy prey for a
grazing sheep. “Its mandibles actually become locked in that position,
so there’s nothing the ant can do except hang there in the air,” says
Flegr. The sheep grazes on the grass and eats the ant; the worm gains
entrance into the ungulate’s gut, which is exactly where it needs to be
in order to complete—as the
Lion King song goes—the circle of
life. “It was the first I learned about this kind of manipulation, so it
made a big impression on me,” Flegr says.
After he read the book, Flegr began to make a connection that, he
readily admits, others might find crazy: his behavior, he noticed,
shared similarities with that of the reckless ant. For example, he says,
he thought nothing of crossing the street in the middle of dense
traffic, “and if cars honked at me, I didn’t jump out of the way.” He
also made no effort to hide his scorn for the Communists who ruled
Czechoslovakia for most of his early adulthood. “It was very risky to
openly speak your mind at that time,” he says. “I was lucky I wasn’t
imprisoned.” And during a research stint in eastern Turkey, when the
strife-torn region frequently erupted in gunfire, he recalls being “very
calm.” In contrast, he says, “my colleagues were terrified. I wondered
what was wrong with myself.”
His bewilderment continued until 1990, when he joined the biology
faculty of Charles University. As it happened, the 650-year-old
institution had long been a world leader in documenting the health
effects of
T. gondii, as well as developing methods for detecting
the parasite. In fact, just as Flegr was arriving, his colleagues were
searching for infected individuals on whom to test their improved
diagnostic kits, which is how he came to be asked one day to roll up his
sleeve and donate blood. He discovered that he had the parasite—and
just possibly, he thought, the key to his baffling self-destructive
streak.
He delved into
T. gondii’s life cycle. After an infected cat
defecates, Flegr learned, the parasite is typically picked up from the
soil by scavenging or grazing animals—notably rodents, pigs, and
cattle—all of which then harbor it in their brain and other body
tissues. Humans, on the other hand, are exposed not only by coming into
contact with litter boxes, but also, he found, by drinking water
contaminated with cat feces, eating unwashed vegetables, or, especially
in Europe, by consuming raw or undercooked meat. Hence the French,
according to Flegr, with their love of steak prepared
saignant—literally,
“bleeding”—can have infection rates as high as 55 percent. (Americans
will be happy to hear that the parasite resides in far fewer of them,
though a still substantial portion: 10 to 20 percent.) Once inside an
animal or human host, the parasite then needs to get back into the cat,
the only place where it can sexually reproduce—and this is when, Flegr
believed, behavioral manipulation might come into play.
|
| The parasite T. gondii,
seen here, may be changing connections between our neurones, altering
how we act and feel. (Dennis Kunkel Microscropy, Inc./Visuals
Unlimited/Corbis Images) |
Researchers had already observed a few peculiarities about rodents with
T. gondii
that bolstered Flegr’s theory. The infected rodents were much more
active in running wheels than uninfected rodents were, suggesting that
they would be more-attractive targets for cats, which are drawn to
fast-moving objects. They also were less wary of predators in exposed
spaces. Little, however, was known about how the latent infection might
influence humans, because we and other large mammals were widely
presumed to be accidental hosts, or, as scientists are fond of putting
it, a “dead end” for the parasite. But even if we were never part of the
parasite’s life cycle, Flegr reasoned, mammals from mouse to man share
the vast majority of their genes, so we might, in a case of mistaken
identity, still be vulnerable to manipulations by the parasite.
In the Soviet-stunted economy, animal studies were way beyond
Flegr’s research budget. But fortunately for him, 30 to 40 percent of
Czechs had the latent form of the disease, so plenty of students were
available “to serve as very cheap experimental animals.” He began by
giving them and their parasite-free peers standardized personality
tests—an inexpensive, if somewhat crude, method of measuring differences
between the groups. In addition, he used a computer-based test to
assess the reaction times of participants, who were instructed to press a
button as soon as a white square popped up anywhere against the dark
background of the monitor.
The subjects who tested positive for the parasite had significantly
delayed reaction times. Flegr was especially surprised to learn,
though, that the protozoan appeared to cause many sex-specific changes
in personality. Compared with uninfected men, males who had the parasite
were more introverted, suspicious, oblivious to other people’s opinions
of them, and inclined to disregard rules. Infected women, on the other
hand, presented in exactly the opposite way: they were more outgoing,
trusting, image-conscious, and rule-abiding than uninfected women.
The findings were so bizarre that Flegr initially assumed his data
must be flawed. So he tested other groups—civilian and military
populations. Again, the same results. Then, in search of more
corroborating evidence, he brought subjects in for further observation
and a battery of tests, in which they were rated by someone ignorant of
their infection status. To assess whether participants valued the
opinions of others, the rater judged how well dressed they appeared to
be. As a measure of gregariousness, participants were asked about the
number of friends they’d interacted with over the past two weeks. To
test whether they were prone to being suspicious, they were asked, among
other things, to drink an unidentified liquid.
The results meshed well with the questionnaire findings. Compared
with uninfected people of the same sex, infected men were more likely to
wear rumpled old clothes; infected women tended to be more meticulously
attired, many showing up for the study in expensive, designer-brand
clothing. Infected men tended to have fewer friends, while infected
women tended to have more. And when it came to downing the mystery
fluid, reports Flegr, “the infected males were much more hesitant than
uninfected men. They wanted to know why they had to do it. Would it harm
them?” In contrast, the infected women were the most trusting of all
subjects. “They just did what they were told,” he says.
Why men and women reacted so differently to the parasite
still mystified him. After consulting the psychological literature, he
started to suspect that heightened anxiety might be the common
denominator underlying their responses. When under emotional strain, he
read, women seek solace through social bonding and nurturing. In the
lingo of psychologists, they’re inclined to “tend and befriend.” Anxious
men, on the other hand, typically respond by withdrawing and becoming
hostile or antisocial. Perhaps he was looking at flip sides of the same
coin.
Closer inspection of Flegr’s reaction-time results revealed that
infected subjects became less attentive and slowed down a minute or so
into the test. This suggested to him that
Toxoplasma might have
an adverse impact on driving, where constant vigilance and fast reflexes
are critical. He launched two major epidemiological studies in the
Czech Republic, one of men and women in the general population and
another of mostly male drivers in the military. Those who tested
positive for the parasite, both studies showed, were about two and a
half times as likely to be in a traffic accident as their uninfected
peers.
W
hen I met Flegr
for the first time, last September, at his office on the third floor of
Charles University’s Biological Sciences building, I was expecting
something of a wild man. But once you get past the riotous red hair, his
style is understated. Thin and slight of build, he’s soft-spoken,
precise with his facts, and—true to his
Toxo status—clad in old
sneakers, faded bell-bottom jeans, and a loose-fitting button-up shirt.
As our conversation proceeds, I discover that his latest findings have
become—to quote
Alice in Wonderland—“curiouser and curiouser,”
which may explain why his forehead has the deep ruts of a chronic
worrier, or someone perpetually perplexed.
He’s published some data, he tells me, that suggest infected males
might have elevated testosterone levels. Possibly for that reason, women
shown photos of these men rate them as more masculine than pictures of
uninfected men. “I want to investigate this more closely to see if it’s
true,” he says. “Also, it could be women find infected men more
attractive. That’s something else we hope to test.”
Meanwhile, two Turkish studies have replicated his studies linking
Toxoplasma to traffic accidents. With up to one-third of the world infected with the parasite, Flegr now calculates that
T. gondii
is a likely factor in several hundred thousand road deaths each year.
In addition, reanalysis of his personality-questionnaire data revealed
that, just like him, many other people who have the latent infection
feel intrepid in dangerous situations. “Maybe,” he says, “that’s another
reason they get into traffic accidents. They don’t have a normal fear
response.”
It’s almost impossible to hear about Flegr’s research without
wondering whether you’re infected—especially if, like me, you’re a cat
owner, favor very rare meat, and identify even a little bit with your
Toxo
sex stereotype. So before coming to Prague, I’d gotten tested for the
parasite, but I didn’t yet know the results. It seemed a good time to
see what his intuition would tell me. “Can you guess from observing
someone whether they have the parasite—myself, for example?,” I ask.
“No,” he says, “the parasite’s effects on personality are very
subtle.” If, as a woman, you were introverted before being infected, he
says, the parasite won’t turn you into a raving extrovert. It might just
make you a little less introverted. “I’m very typical of
Toxoplasma males,”
he continues. “But I don’t know whether my personality traits have
anything to do with the infection. It’s impossible to say for any one
individual. You usually need about 50 people who are infected and 50 who
are not, in order to see a statistically significant difference. The
vast majority of people will have no idea they’re infected.”
Still, he concedes, the parasite could be very bad news for a small
percentage of people—and not just those who might be at greater risk
for car accidents. Many schizophrenia patients show shrinkage in parts
of their cerebral cortex, and Flegr thinks the protozoan may be to blame
for that. He hands me a recently published paper on the topic that he
co-authored with colleagues at Charles University, including a
psychiatrist named Jiri Horacek. Twelve of 44 schizophrenia patients who
underwent MRI scans, the team found, had reduced gray matter in the
brain—and the decrease occurred almost exclusively in those who tested
positive for
T. gondii. After reading the abstract, I must look
stunned, because Flegr smiles and says, “Jiri had the same response. I
don’t think he believed it could be true.” When I later speak with
Horacek, he admits to having been skeptical about Flegr’s theory at the
outset. When they merged the MRI results with the infection data,
however, he went from being a doubter to being a believer. “I was amazed
at how pronounced the effect was,” he says. “To me that suggests the
parasite may trigger schizophrenia in genetically susceptible people.”
