[Levin]

By Ben Thomas Oct 29, 2015 10:00 PM



The Feline Parasite

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T. gondii’s life begins in cat feces, where its eggs (known as “oocytes” or “egg cells”) wait to be picked up by carriers like rats. Once they’re safe and warm in the guts of their temporary hosts, the oocytes morph into tachyzoites, the unassuming little blobs that can really do some damage. Those tachyzoites migrate into their hosts’ muscles, eyes and brains, where they can remain hidden for decades without doing much of anything.

But when the moment comes to strike, the little T. gondii tachyzoites alter their hosts’ brain chemistry. Infected rats actually become sexually aroused by the smell of cats, and leap fearlessly into their claws, where they die and release the tachyzoites back into the cats, allowing the egg-laying cycle to start anew.

Creepy, perhaps, but not exactly the stuff of nightmares — except that rats aren’t the only hosts in which T. gondii hibernates. Some researchers estimate that as much as 30 percent of the people on earth — more than two billion of us — are carrying little T. gondii tachyzoites around in our brains right now.

What might this mean for human behavior? Just as a start, some studies have found that cases of schizophrenia rose sharply around the turn of the twentieth century, when domestic cat ownership became common.

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these tiny parasites could cumulatively alter the behavioral patterns of entire cultures. Infected parents, researchers found, have a 30 percent chance of passing the parasite on to their children.


https://www.discovermagazine.com/planet-...man-brains



Toxoplasma infection was 2.4 fold more common in people who had a history of manic and depression symptoms (bipolar disorder Type 1) compared to the general population.

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Research on the linkage between T. gondii infection and entrepreneurial behavior showed that students who tested positive for T. gondii exposure were 1.4 times more likely to major in business and 1.7 times more likely to have an emphasis in "management and entrepreneurship". Among 197 participants of entrepreneurship events, T. gondii exposure was correlated with being 1.8 times more likely to have started their own business.


https://en.wikipedia.org/wiki/Toxoplasma_gondii

[Levin]

The Amoeba of Madness


If you’re hiking in the wilderness, stay away from warm, stagnant bodies of fresh water, no matter how thirsty you are. These inviting little ponds often play host to Naegleria fowleri, an amoeba species with a taste for human brain tissue.

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N. fowleri sprouts a “sucking apparatus” called an amoebostome and starts chowing down on juicy brain matter. As the amoeba divides, multiplies and moves inward, devouring brain cells as it goes, its hosts can go from uncomfortable to incoherent to unconscious in a matter of hours.


https://www.discovermagazine.com/planet-...man-brains

[Levin]

The Virus That Brings Fear


We’ve all been warned to stay clear of wild cats and dogs, and never to bother animals we find wandering the streets of a city. Friendly as they might look, they could easily be carrying the deadly rabies virus, which doesn’t always cause the telltale mouth-foaming — though it does alter its victims’ brain functions in profound ways.

This bullet-shaped virus — so small and sneaky that it often escapes detection by the immune system — doesn’t need much of an invitation to dive into a new host; a simple puncture wound will do it. Once it’s inside the host’s bloodstream, it quickly starts taking over cells, transforming them into rabies factories that churn out thousands of copies of the virus. As the attackers grow in number, they make their way to the host’s central nervous system, and head for the brain.

But rabies viruses don’t just settle down anywhere in the brain, they specifically seek out the hippocampus, amygdala and hypothalamus, brain structures that play central roles in memory, fear and emotion. And they don’t just devour brain cells indiscriminately, either; instead, they alter the ways these cells release neurotransmitters like serotonin, GABA, and endogenous opioids. In other words, they turn their hosts’ own brain chemistry against them.

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Human rabies patients become terrified of water and puffs of air, both of which make them flinch and twitch uncontrollably.

If the infection goes untreated, rabies patients fall deeper into confusion and hallucination, lashing out at imagined threats and hapless bystanders. They lose their ability to sleep, sweat profusely, and finally fall into a paralyzed stupor as their brain function slips into chaos. A few days later, as the paralysis reaches their hearts and lungs, they fall into a coma and die.

Once rabies has infected a human, survival is all-but impossible.


https://www.discovermagazine.com/planet-...man-brains

[Levin]

The Parasite of Sleep


In the villages of sub-Saharan Africa and the wilds of the Amazon, the tiniest insect can bring a sleep that leads to death. The tsetse fly loves the taste of human blood, and it often carries a parasite known as Trypanosoma, whose tastes run more toward human brains.

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As they mature, the parasites cross the blood-brain barrier and the encephalitic stage begins. The Trypanosoma alter the structure and function of their hosts’ brain cells (the parasites seem have a particular penchant for the hypothalamus, which helps regulate our mood and sleep/wake cycles) and the hosts start to feel and behave strangely. First they suffer headaches and have trouble sleeping, or sleep and wake at odd hours, due to the parasite’s alteration of the rhythm in which the sleep hormone melatonin gets released.

Before long, though, human hosts start to exhibit a dizzying variety of other psychological symptoms, from changing appetites to depression to odd speech patterns to uncontrollable itching and tremors. Over the next few years, the host’s odd behavior gradually starts to lapse into laziness, unresponsiveness, and finally a prolonged sleep that leads to coma and death, hence the name “sleeping sickness.”


https://www.discovermagazine.com/planet-...man-brains