Crazy Cats and Brain Parasites


Brain parasitesIt reads like a script for a scary movie: an alien parasite invading our brains, taking control of our minds, changing our behaviour silently, secretly; making us do what it wants. And it’s happening now, in homes across Canada and the USA. Alien puppet masters over-running the nation, one household at a time.

But it’s not fiction, although my scenario is a trifle exaggerated.

They’re not some right-wing aliens from outer space subverting our natural goodness and compassion; not some cyber-bullying bloggers dripping political poison into the gullible minds of their readers.They are microscopic, found worldwide, on land and in water – including saltwater – and may be infecting people you know this very minute. Or even you. They’re Toxoplasma gondii; an amoebic parasite pretty much capable of infecting any warm-blooded creature.

Where they breed, however, is in your cat, and are then excreted in their feces:

Although T. gondii can infect, be transmitted by, and asexually reproduce within humans and virtually all other warm-blooded animals, the parasite can sexually reproduce only within the intestines of members of the cat family (felids). Felids are therefore defined as the definitive hosts of T. gondii, with all other hosts defined as intermediate hosts.

As an owner of four cats and having had cats most of my life, this is troubling. But not entirely new. Back in 2012, in an article in The Atlantic, titled, “How Your Cat Is Making You Crazy,” Kathleen MacAuliffe wrote:

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.”

To be fair to cats, the parasites live in soil, too, so they’re hard to avoid. Plus they’re also found in undercooked meat. You like your steak blue? Or bloody rare? You may be inviting this parasite into your brain. And also if you drink contaminated water or eat uncooked or undercooked shellfish. Those raw oysters you love? Parasite havens. Yum.

In the ocean, the parasites’ eggs (from cat feces, wild and domestic) are carried on “sticky polymers” – the slime on seaweed – which is eaten by snails. These are in turn eaten by sea otters, and then excreted into coastal waters there they are picked up by shellfish – the sort you eat. (I’ll get back to this a bit later in the post: algae may play a role in this and in another worrisome virus: Chlorovirus, which may also be affecting your brain.)

The Care2 website posted a suggestion that, if people realized the danger their garbage (and pets) posed, they might change their habits::

…she hopes the study will help us alter our behavior with small changes like keeping cats indoors and putting litter in the trash, instead of burying it or flushing it, and that it will make us rethink dumping trash offshore.

Personally, I’d suggest the response to her optimism would be best encapsulated in the phrase, “fat chance.” Humans seldom change their behaviour if it’s inconvenient, more work, requires more thought or interferes with TV watching.

The Smithsonian explains how the parasite spreads itself into cats:

One way for the parasite to reach its feline host is to infect rodents. When the parasite infects the rodent’s brain, it removes the rat’s innate fear of cats. So instead of running away when they smell a cat, these rats are undisturbed by the risk of being eaten. This lack of fear increases the chance that the rodent will become dinner for a feline predator, completing the parasite’s life cycle.

An anti-cat diatribe on Vox, noted this:

Of course, we’re not rodents, so the parasites aren’t successful in getting us eaten by cats. But the actual consequences are just as troubling. People who have been infected have greater rates of neuroticism and schizophrenia, and have slower reflex times in lab experiments. As a result, it seems, they get into traffic accidents more often. There’s evidence that they have higher rates of suicide. All this, it seems, are unintended results of the parasite’s ability to alter a mouse’s brain to increase the chance of predation.
Now, everyone who owns a cat doesn’t get infected by T. gondii, and there are other ways of getting the parasite (like eating undercooked meat). And the infection itself doesn’t seem to cause these behavioral changes in everyone — they just occur at slightly higher rates among the millions of people worldwide who are infected.

Some surprising and potentially scary results are emerging from research into human infections that suggests something that may provide a shake up in psychology and even psychiatry. A story in Medical News Today, back in late 2012, noted:

Infection by Toxoplasma gondii or Toxoplasma is called Toxoplasmosis. Estimates suggest between 30 and 50% of the global human population is infected. In Sweden the figure is nearer 20%. In the US, the Centers for Disease Control and Prevention (CDC), puts the number of infected men, women and children at 60 million. Animals can also become infected, especially domestic cats.
Other studies have found schizophrenia, depression, anxiety, and other mental diseases are more common in people with toxoplasmosis, and there is also evidence to suggest infection by the parasite is linked to more extroverted, aggressive and risk-taking behavior… rats infected with the parasite lose their fear of cats, and are even attracted by their scent, making them easy prey. Scientists have suggested this is how the parasite assures its own survival and propagation: the cats eat the infected rats, shed more parasite through their feces, and that in turn helps to infect more rats…
The researchers didn’t examine how the toxoplasmosis parasite changes host behavior, they were more interested in what it does in the brain.
They found that it takes over one of the brain’s neurotransmitters: the chemical messengers that carry signals between various parts of the brain.

Last week, Medical News Today published a follow-up story that added:

A parasite responsible for toxoplasmosis – Toxoplasma gondii – may be involved in the cause of around a fifth of schizophrenia cases in the US. This is according to a new study published in the journal Preventive Veterinary Medicine.

National Geographic put a sensationalist spin on it last month:

The best known mindsucking parasite plays out a similar manipulation on land. Along with other mammal species, rats and mice can be infected with Toxoplasma gondii, a single-celled relative of malaria-causing Plasmodium. The parasite can form thousands of cysts in the brain of its host. To take the next step in its life cycle, Toxoplasma has to get inside the gut of a cat. Toxoplasma doesn’t have the means to transport itself from a rat’s brain to a cat’s gut. But if its rat host gets eaten by a cat, the parasite can reproduce. Scientists have discovered that rats infected with Toxoplasma lose their normal fear of the smell of cats. In fact some infected rats become downright curious about the odor of cat urine, making themselves easy targets for a swipe of a cat’s paw—and thus raising the odds that Toxoplasma will advance through its life cycle.

A piece in the Daily Mail last month added:

People with HIV or other diseases that weaken the immune system are susceptible to a complication of T. gondii infection called toxoplasmic encephalitis, which can be deadly.
While it has long been believed that most healthy people suffer no adverse effects from a T. gondii infection, recent studies have found evidence of worrying impacts, including an association with schizophrenia, because the parasite is found in in the brain as well as in muscles.
Some antipsychotic drugs can stop the parasite from reproducing, but studies in mice, rats and people have also shown that infection with T. gondii triggers changes in behaviour and personality.

Back a few paragraphs, I mentioned Chlorovirus. It’s a virus found in algae that can infect humans. ANd in doing so, it affects our cognitive abilities. A story last month in Science Magazine noted:

…researchers have discovered that even a virus found in the lowly algae can make mammals its home. The invader doesn’t make people or mice sick, but it does seem to slow specific brain activities.
The virus, called ATCV-1, showed up in human brain tissue several years ago, but at the time researchers could not be sure whether it had entered the tissue before or after the people died. Then, it showed up again in a survey of microbes and viruses in the throats of people with psychiatric disease…
The researchers wanted to find out if the virus was in healthy people as well as sick people. They checked for it in 92 healthy people participating in a study of cognitive function and found it in 43% of them. What’s more, those infected with the virus performed 10% worse than uninfected people on tests requiring visual processing. They were slower in drawing a line connecting a sequence of numbers randomly placed on a page, for example. And they seemed to have shorter attention spans, the researchers report online today in the Proceedings of the National Academy of Sciences. The effects were modest, but significant.

More sensationally (as is their wont), the Daily Mail headlined a story about it: “Algae disease is discovered in human throats – and may be linked to poor brain function,” adding,

The researchers found that people infected with ATCV-1 performed ‘measurbly lower’ in a set of tasks measuring the speed and accuracy of visual processing, than healthy people.
For example, people who harboured the virus scored, on average, nearly nine points lower on a test that measured how quickly they could draw a line between sequentially numbered circles on a piece of paper. Viral carriers also scored an average of seven points lower on tests measuring attention.
To extend the study, the scientists infected a group of mice and analysed their performance during a battery of tests designed to measure their brain power.
Animals infected with the virus exhibited deficits similar to those observed in humans, including lesser recognition memory and spatial awareness…
The virus also seems to change the expression of multiple genes found in the hippocampus, which is the part of the brain that sorts and catalogues short-term and long-term memories and guides spatial orientation.
The discovery sheds new light on class of viruses that has been previously been deemed non-infectious to humans, highlighting the ability of certain microorganisms to trigger delicate physiologic changes without causing full-blown disease.

I suspect there will be more connections between viruses or parasites and behaviour and brain activity found in the next few years. Perhaps at the same time, researchers will uncover ways to combat them or even immunize ourselves against them. But I suspect the anti-vaxxer crowd is already infected with a brain parasite and the behaviour modification the parasite has wrought has been to make them suspicious of vaccinations. So they will continue to be the willing hosts of mind-bending brain parasites.

Perhaps one day we will discover that gullibility on the internet is caused by  brain parasites. Conspiracy theories were caused by viruses. All of which could be easily cured by a regime of chemical therapy. After a few weeks on drugs, people would no longer be so stupid they feared vaccinations or wrote angry ad hominem blog posts.

Ah, if only it were all so simple.

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Ian Chadwick
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