Meet the Parasites That Control Human Brains

By Ben Thomas | October 29, 2015 9:00 am
brain illustration

(Illustration credit: Triff/Shutterstock)

It’s time to enjoy some monster stories, and the scariest monsters of all are those that actually exist.

Join us as we share tales of some of the creepiest parasites around — those that control the brains of their human hosts, sometimes leaving insanity and death in their wake. These are the tales of neurological parasites.

The Feline Parasite

Toxoplasma gondii tops the list as the most famous — and most controversial — neurological parasite. This tiny protozoan doesn’t look like much more than a blob, but once it makes its way to the brain, it can radically alter the behavior of hosts like rats, cats and, yes, even humans.

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.

Microscopic cysts containing Toxoplasma gondii

Microscopic cysts containing Toxoplasma gondii in mouse brain tissue (Credit: Jitender P. Dubey/USDA)

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.

“We often see symptoms like altered activity levels, changes in risk behaviors, and decreased reaction times,” says Joanne Webster, a parasitology researcher at Imperial College, London. “But in some cases, they become more severe — like schizophrenia.”

Another paper, published in the journal Proceedings of the Royal Society B, argued that in areas with high T. gondii infection rates, 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.

If that all seems a little far from home, though, consider this: Researchers estimate that more than 60 million people in the U.S. alone currently carry T. gondii, and most of those have no idea, because the parasite often causes no symptoms at all. Until the day it strikes, that is.

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.

N. fowleri can spend long spans of time just hanging around as a cyst, a little armored ball that can survive cold, heat, and dry conditions. When a cyst comes into contact with an inviting host, it sprouts tentacle-like pseudopods and turns into a form known as a trophozoite. Once it’s transformed, the trophozoite heads straight for the host’s central nervous system, following nerve fibers inward in search of the brain.

 Naegleria fowleri damage

Damage (black cavities) caused by Naegleria fowleri as seen in a brain tissue sample. (Credit: Dr. Martin D. Hicklin, USCDCP)

Once it’s burrowed into its host’s brain tissue — usually the olfactory bulbs — 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.

The symptoms start subtly, with alterations in tastes and smells, and maybe some fever and stiffness. But over the next few days, as N. fowleri burrows deeper into the brain’s cognitive structures, victims start feeling confused, have trouble paying attention, and begin to hallucinate. Next come seizures and unconsciousness, as the brain loses all control. Two weeks later, the victim’s most likely perishes — although one man in Taiwan managed to stick it out for a grueling 25 days before his nervous system finally gave out.

Although N. fowleri infections are rare in the extreme — worldwide historical totals number only in the hundreds — they’re almost always fatal, and tricky to catch and treat before they spiral out of control. Even so, you’d be wise to avoid warm pools of still water, lest you end up with an uninvited guest on the brain.

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.

A dog suspected of being rabid

A dog suspected of being rabid that had been exhibiting signs of restlessness, and overall uncharacteristic aggressive behavior. (Credit: CDC)

In the altered states brought on by a rabies infection, animals often lash out at any nearby living thing, but this may be more out of fear than anger. 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. To date, fewer than 10 people have survived a clinical-stage rabies infection — ever, in history. Many doctors consider the disease untreatable. The better news, though, is that it’s easily preventable with a vaccine. If you plan on traveling anywhere wild animals roam, you’d do well to go protected.

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.

Parasites of the genus Trypanosoma start their lives in the guts of invertebrate hosts, but quickly develop through a series of increasingly complex forms when they come into contact with the mammalian fluids they crave. In the first stage of infection, known as the haemolymphatic stage, the parasites live in the host’s blood and lymph nodes, where they grow from nondescript little ovals into long squirmy splotches equipped with whip-like flagellae.

Trypanosoma lewisi flagellate parasites

Trypanosoma lewisi flagellate parasites (red, hooked cells) in a blood sample (maginfied 1000x). (Credit: CDC/ Dr. Mae Melvin)

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.”

Although a cure for trypanosomiasis exists, victims’ friends and families often fail to catch the disease early enough, and for a very simple reason: The sheer range and unpredictability of the infection’s symptoms makes it extremely hard to recognize. If you had a friend who suddenly started waking at odd hours and eating less, would your first thought be, “He probably has a protozoan invading his brain?” No, you’d think, “He’s probably depressed,” which is exactly what the friends and families of most Trypanosoma hosts think — until it’s too late.

Scientific fact, as so often happens, is stranger than fiction when it comes to these parasites. From worms that devour brain cells to viruses that bring on crippling paranoia, these creatures are every bit as ghoulish as those in any fireside ghost story.

“The brain is a ‘privileged site’ for many parasites,” Webster says. “And that really challenges the concept of free will — after all, is it us or our parasites who ‘decide’ our behavior?”

With that in mind — no pun intended — have a frightfully wonderful Halloween night, and don’t let the neurological parasites bite!

CATEGORIZED UNDER: Living World, Mind & Brain, Top Posts
  • Uncle Al

    The mere idea that Toxoplasma gondii causes cultural mental diseases curable with azithromycin or pyrimethamine plus sulfadiazine makes a mockery of psychology and psychiatry. It must be vigorously suppressed lest respected professions be revealed as beads and rattles.

    • rashibenanshul

      You are absolutely correct Uncle Al. Psychiatry uses a single hammer, and that is psychotropic drugs. When one does not work, they try another. The almost never consider the possibility of T. gondii.

      • Jermel Clark

        I am a victim of psychiatry. It took years for me to develop the insight to convince a trained veteran psychiatrist to accept my diagnosis. At one point I was prescribed Thorazine, and this continued with no benefit to me for years. I suffered tardive dyskinesia, and the psychiatrists remained obdurate. Now, I am being treated with Buspirone and Strattera. I have a lot less problems as a result, but I am 44 years old, so the solution came a little late for me. I do find it interesting, there has been a spike in depression and Toxoplasmosis is about. The real issue is the ability of a psychologist or psychiatrist to diagnose symptoms. People have their own biases, and what I found is that most psychiatrists go on the word of other psychiatrists, so there is often no examination performed. I argued with a psychiatrist who was convinced that I should take some form of neuroleptic, because she wasn’t as intelligent as me. So, in her case Dr. Trixi Lipke was able to fellate her way to success. Malpractice insurance premiums are so inordinately high, because you have literal idiots practicing medicine. In other forms of medicine they have tests they can perform, although there are a battery of psychological tests, the results are subject to the inherent biases of the interpreter. Alzheimer’s and Toxoplasmosis….

      • Theodore Roosevelt

        I thought the single hammer in psychiatry is the literal hammer used to hit a leukotome. I stand corrected.

    • JohnnyMorales

      Yes because ideas in science are dangerous, especially ideas that attach any sort of risk to having a cats as pets.

      According to the CDC and the Mayo Clinic you’re wrong as usual.

      Toxoplasmosis cannot be cured, because it has a cyst form that cannot be killed by any drugs, and there are always a few cysts in any infection.

      The best the drugs can do is force an active, symptom causing case into submission by killing all the active parasites in the system.

      Any in cyst form remain alive and able to trigger a future infection.

      Only immunocompromised, the old, the sick Etc. the usual group of susceptible individuals really have to worry though.

      For the vast majority it is a symptom free infection after a possible mild initial infection response.

      The fact that it is symptom free for the most part makes taking those horrific antibiotics you so casually mistakenly mention as cures for treatment simply not worth the agony they cause most people in the developed world. In the 3rd. world that option is simply not available to be much of a solution.

      Perhaps the proof that gondi can control and direct human behavior can be found in you. Your comments on the parasite, and comments defending cats their true host against anything that might be construed as negative certainly is in their best interests of the parasite.

      • Laren Ganer

        The drugs he listed are actually in fact the recommended treatment for toxoplasmosis, though. And, uh, azithromycin and sulfa-based antibiotics aren’t horrific at all. Azithromycin is a very well tolerated antibiotic, in fact.

        I’m not agreeing even remotely with his original comment, but I feel it’s important to rebut the idea that these are “horrific” drugs. And this is from someone who detests taking antibiotics. DETESTS. I will do almost anything before I take antibiotics.

        • Krissy Anderson

          I agree – hate antibiotics, but I was so over-prescribed when I was younger I am now resistant to all of them except Ertapenum. So I live with a sinus infection and an infection in my eyes all the time. I am exhausted and have developed ME/CFS. Just reading this article because it’s interesting, but who do you believe on the Internet? I am a writer and involved in some heavy research, and the CDC, NIH, etc. all are going in a million directions with their facts.

    • AlDavisJr

      It is illuminating to read the response to your supposition, Uncle Al. Seems like the posts that agree with you are from people that think they know everything, but in actuality, don’t know their arses from a hole in the ground.

    • gseattle

      Toxo is what makes internet trolls so ill-mannered, theory.

      Not sure I understand your comment.
      I think those two professions will have to get in gear about Toxoplasmosis. If/when they do, they’ll no longer be so easy to mock and can do a ton of good.
      Toxoplasma plays far more widespread roles in our lives than we think, I think. Many a ruined relationship for example.

    • John Fall

      psycology and psyciatry often make a mockery of themselves by failing to teach people they have 100% control over their thoughts, without the aid of a college degree. And further, that a habitual positive mindset (which is always a choice), augmented with prayer, fasting and choosing 100% positive, constructive relationships and environments works often; albeit not immediately. Some of the dumbest, most incompetent and closed- minded people are in those professions. The rare competent person, is usually because they learned outside the extremely limited knowledge base within the profession.

  • Ahmad

    is there an anti Toxoplasma gondii anything?

    • Jim Blake

      20 years of Freudian psychotherapy and cocktail of anit-schizophrenia / bipolar drugs from big pharma

      • gseattle

        If SSRI drugs tamp down Toxoplasma in the brain … then the person stops taking them … then the parasites emerge from their cysts, running wild, eating, pooping, driving the person mad … then that person becomes a shooter …
        The dots connect.

    • gseattle

      They say we have nothing that will dissolve the cyst walls where Toxo hides out, possibly indefinitely. When one’s immune system is lowered for some reason, they apparently can leave the cyst, doing damage (messing with one’s head) and return.

      When cysts enter a cat gut the cyst walls are dissolved by proteolytic enzymes. An example of one of those is papain in papaya. Do they not cross the blood-brain barrier? Would that it were as simple as eating papaya while taking pyrimethamine and leucovorin which kills Toxoplasma (outside of cysts), just can’t make it through that cyst wall.

  • the_professeur

    Nothing mentioned here that a bowl of good chicken soup couldn’t take care of…

    • Mary Murray

      Really??????? Wish I’d known about that Dec. 19th, 2014 when I lost my 32 year old son, who would’ve thought, simple as chicken soup!!!!!

      • Carolyn Pikientio

        Iam so sorry!! I saw this on Dr Oz and was not sure if it was true, I have never heard of this before! Do you know where your son contracted this?

        • Mary Murray

          My son had been in a terrible car/train accident and was thrown 100 ft from the vehicle resulting in massive road rash with a huge amount of dirt, asphalt and pebbles ground into his body…. once this parasite enters the blood stream it travels to the brain and feeds from the brain until it causes death in the individual….it is a very gruesome and slow process to witness….it is very true…..I wish to God it wasn’t…my son was 32….it is called Balamuthia and has a 99% mortality rate…

          • Carolyn Pikientio

            I’m so sorry! Can people be tested for this parasite now?

          • Carolyn Pikientio

            I’m sorry, that is not applicable, I was thinking of toxoplasma gondii?

          • Mary Murray

            Thank you Carolyn…if you look this up on the CDC website they will have the information for you to consider…. symptoms and contact information…. it’s not an easy diagnosis….. I will be happy to answer any questions i possibly can….

  • cnels

    OMG, you’re all so cynical! Is there a cynicism-causing parasite? Really, people – lighten up!

  • domo brown

    Its amazing how these little parasites can affect the brain in many and different ways. Like with the Toxoplasma Gondii causes a serious different brain behavior in human let alone animals. I never even know that 30% of humans even carry the parasite with them. In my psych class we are learning about how the brain develops. an this article is the perfect way of showing how different things affect the brain and its behaviors that come with it.

  • OWilson

    I thought the headline referred to the NEA :)

  • OWilson

    The difference is, those influences are voluntary, you can switch off the channel as you choose.

    However, unionized teachers are mandatory for most of society.

    (The Left figured that out 100 years ago) :)

    • jimmyxsan

      Yeah, those scary unionized English, Math and Science teachers. You gotta be careful, they might teach your children to think!

      • OWilson

        Or keep them on the plantation, in urban illiterate crime infested, gang banging ghettos to be milked for votes :)

        • jimmyxsan

          Spent two years of my life teaching Chemistry in one of those urban “ghettos”. I can promise you it was not my mission to keep “them” there to be “milked” for anything. In fact, I helped get several of them to college.

          But keep drinking the Fox-news Kool-Aid if it helps you get through life. While you are whinging, fear-mongering, and spreading dissension, the rest of us will be busy working to make it better.

          • OWilson

            Thank you for your service!

          • OWilson

            I’ll give you guys the last word, because I’ve heard it all before.

            I’m outa here!

          • Mike Richardson

            Bye! :)

          • OWilson

            Polly want a cracker? :)

          • Mike Richardson

            Thought you were out of here. Oh well, originality hasn’t been one of your favorite things around here, either, what with the endless “gang-banging ghettoes,” “low information,” “cultists,” etc. But you can always consider the “imitation is the sincerest form of flattery” possibility, if it makes you feel better. :)

          • John Gallien

            Well, this is the real deal. Yes, there are some good teachers in public schools. The problem, by and large, is not with the people. The problem is there is no competition and therefore little motivation to get better. Imagine if you were a company that had a “decent” product and were essentially immune from any other company improving on that product (it’s considered decent only because there is nothing to compare it to). You could fiddle around with it, do different things, make it worse or maybe even slightly better (who would know – you could only compare the success of the product or service to how things were in the past, if you decided to look at such things). But it really doesn’t matter because no one else is allowed to offer a product that would compete with it, so you really don’t know what could have been. The product works, so why spend the resources to make it better. You could be as conscientious as possible in that environment and actually think you are doing a good job (good vs. what, by what measure?), but until someone is allowed to compete with you and potentially come up with a better product, your incentive to improve will only come from your own inner motivation, assuming you have it (it is not required for business survival in this environment). There would be no motivation from the possibility that another company could come up with a better product or service that could put you out of business (a real motivator – believe me, I’ve seen it in the private sector over what most people would consider trivial things – any small improvement to offer a better product in order to improve sales and maintain or improve market share is the motivation). By the way, while some may call this “dog eat dog” competition, it’s really about freedom. The free market is about freedom first. The competition is secondary as free people might be attracted to the same sort of business or interests. However, it is this competition that acts as a strong motivation for improvement and bring out the best in people, and therefore result in the best possible products and services. The “best” might not be the “best” for all people, as differences in products and services may appeal to different people – look at all the products we have today to choose from.
            This is the status of public education today. Public education essentially has a monopoly because the vast majority of parents cannot afford the alternative after the government has taken so much in taxes from them to support “free” public education. In the free market, a school would have to constantly improve in all areas to continually have the better or best product; and they couldn’t force you to pay for their product whether you used it or not as public schools do. Private schools (grades 1 through 12) are just a small part of the education system today, controlled to a large extent by the much larger public school system, and are at an economic disadvantage, and therefore offer little competition to the public school system. In a true free market, you wouldn’t just have competition for a better quality product, you would have competition to provide that service/product at the lowest possible price. So school systems, for example, wouldn’t be packed with administrators, but with people that actually bring educational value (not that administrators don’t do this, it’s just that every single job would need to be justified every single day so that the school could remain competitive). All sorts of educational approaches would come out of this – some better for certain types of students, others better for different types of students. It wouldn’t be one size fits all. Parents could move their children out of schools that weren’t performing. And, all the arguments about what should and shouldn’t be taught in public schools, and how it should be taught, would go away, as parents could choose among various options in private schools. And don’t tell me poor kids wouldn’t be educated. Poor people in America have all sorts of devices (TVs, computers, cell phones, etc.) and they would get better education than they do today. The cost of education would be dramatically lower. This is how a true free market works, something we not only lack in education, but unfortunately in many other sectors as well.

          • OWilson

            That free market stuff is only for creative, productive (to society) intelligent individuals, who understands what success is and how to achieve it. There are only a few of us, success is relatively rare.

            Most are complacent and happy to let others do the thinking for them and happy to get “free” stuff from whoever will give it to them.

            They really don’t care who actually pays for it in the end, because they won’t be around.

            It explains why they will happily vote for a serial congenital liar, and take the word of a serial sex abuser or enabler as gospel, either in the WH or at the UN.

          • Callme King

            Hey people there is a cure I clearly know because I had them and extracted them with prayer rigorous cleaning routine that has to be done for a 60 day routine that is very difficult to do. Message me if u need to know I did it for 47 days and it came back because I missed one day of hot hot epsom salt bath

          • Drophammer77

            I started taking epsom salt baths that has menthol in it. I also put hydrogfen peroxide in a bowl with mule team borax powder soap and baby shampoo. 3years of being turned away by Doctor’s and Specalist and almost, again almost lost my job I did research on dewormer for cattle and taking vermox from Mexico. I’m so very careful on dosage as I understand worse case scenario, but I had no choice. 3months now and I have passed the unimaginable and continue. Why then when I show video of clearly seen black threads coming out ulcers and pores to Doctors they say “I have never seen anything like that in my Life.” Yet they don’t direct me where to go for help.?? Have had Lab. Technicians call me with worried voice asking “Where did these specimens come from? Has anyone contacted you???” Yet next day Doctor calls me and says “The y didn’t find anything in specimen container.” Well what about that head I coughed up that I showed you video of?! That was in there!” Doctor’s reply was “I don’t know I’m just telling you what I was told.”
            I don’t understand it. ..

        • Mike Richardson

          Lol… gang banging ghettos. And the right wing just can’t figure out why minority outreach seems to be failing for them. I hope they don’t think Ben Carson’s going to change that, since he seems to be appealing more to irrational religious fanatics than to any other group. Yup, it’s gotta be teachers collectively bargaining for good wages that’s caused the problem, not apathy and outright hostility to minorities and the poor from the far right.

          • AlDavisJr

            Mike—yours is one of the sane posts here. Ben Carson is a wing-dinger. He thinks the pyramids were granaries. Says so in the Holy Babble!! snort

          • OWilson

            God help us!

            (and I’m an atheist! :)

          • OWilson

            We don’t want them dependent for life on free government handouts.

            That’s not too politically popular these days. :)

          • Mike Richardson

            If Carson wouldn’t say crazy things every time he opens his mouth, he might not find himself facing criticism. Nothing wrong with someone being a role model, but being sane, honest, and ethical might be nice prerequisites. Your list wasn’t exactly impressive in that category. :)

          • OWilson

            Maybe if he was channeling Rambo, imagining dodging sniper fire, or wiping his bathroom email server he would be more to your taste :)

            Maybe if his lawyer had committed “suicide”, his business partners and Associate Attorney General all in jail, and his spouse a serial sex harasser, who was fined, Impeached and disbarred.

            He could be the Democratic front runner :) :)

            You just made laugh of the day, and you’ve no idea why ! :)

          • Mike Richardson

            I’m sure you laugh at quite a few things other people don’t get, or at least see or hear. But if they look at you funny, just keep laughing and tell yourself it’s all on them, not you. :)

          • Roy Niles

            Good people like Clarence Thomas? Ouch.
            Ben Carson? Oucher.

          • OWilson

            Sound of crickets :)

          • John Gallien

            Ya, right. Not a Ben Carson fan either, nor a fan of the religious right. But, of course, you have to portray anyone that disagree with you as some sort of loony tune and hate monger. The thing is, Leftists don’t understand individual rights, especially when it comes to the economy (nor do many conservatives for that matter), and what the free market really is about. For a brief explanation from the perspective of public education, see my comments above.

  • Bob Juniper

    I wondered why it seems that everyone has gone crazy in the last few years. Parasites.

    • 1064nm

      Obama voters. Sorry.

  • Charles Wittenbraker III

    Never argue parasitism with a lib. They have it down to an art form.

    • 1064nm

      We have seen the enemy, and they are them.

  • JohnBoy

    Who’s this Rupert Murdock? I’ve never heard of him.

    • TecumsehUnfaced

      I wish I had never heard of Rupert Murdoch either. He wouldn’t even make good cat food.

      • JohnBoy

        Do you think he should be in the dock?

        • TecumsehUnfaced

          So you did hear of him?

          • JohnBoy

            Murdoch, yes. Murdock, no.

  • Hope

    Laziness? Really? Since laziness is considered a character flaw and not a physical symptom, how about “lethargy” instead?

    • JohnnyMorales

      Since when did the use of that word become so absolute and restricted.

      As usual with most words, CONTEXT matters when it comes to deciding whether or not it is proper to use it.

      In this context how the word is used is correct. His article is about physical symptoms. It’s not an article on psychology or character. So to use the meaning you think it has in every context would be wrong.

      Using laziness also ties it to what is said in the following paragraph that describes how early signs of infection are missed due to people assuming falsely about the causes for the change in behavior of infected individuals. Laziness is what would come to mind to those people rather than symptoms of lethargy.

      Though perhaps you are right, maybe there is only one meaning for that word. That would mean all the literature that describes the Mississippi as lazy are descriptions of the river’s character flaws instead of a description of its slow rate of flow. LOL

  • Small_Businessman

    Yea, they’ve very bad for you. People who watch them actually think – instead of just drinking the lib kool-ade. And thinking people are dangerous!

  • Donna Hazelwood Hart

    The parasites that control human brains are actually Obama and liberalism, and I see it has infected yours, Shamanomaha. Darned shame.

    • jimmyxsan

      The idea that we should all work together to help each other out is indeed a viral meme. Spread early on by a guy named Jesus, I think.

      • OWilson

        Works best if the next guy doesn’t want to blow up. rape, behead and otherwise do bad things to your children.

      • yor mom

        “‘Don’t I have the right to do what I want with my own money? Or are you envious because I am generous?’”

        • Anela Tea-ana Claiborne

          Mom gives to whom she wants no problem

    • Shamanomaha

      Pitiful, Donna. Just pitiful. Go vote more tax cuts for the 1% and more money for defense. Vote for decreases in your Social Security. Come back in a few years and tell me how it’s working out for you.

      • Donna Hazelwood Hart

        If you do not think we need more money for defense, you have drank way too much of the koolaid. And the government has stolen so much from our Social Security, that it will become insolvent soon.

  • Overburdened_Planet

    So cat lady gets a nod? 😉

  • 1064nm

    Spoken like a hard-line liberal. How’s our “fundamentally transformed” nation sitting with you?


    The statement “once it’sin the host’s bloodstream” is false. The virus, after being bitten by a “rabid” animal which is SHEDDING virus in its saliva, “finds” nerve tissue (in the hand, leg, arm, etc) and infects nerve cells. It is not motile, unable to “move” by its own mechanism. But after it is reproduced by each nerve cell, it moves on to the next, and so on, until it reaches the Central Nervous System, where it’s on its way to the brain, itself. As it “takes over” the amygdala, feelings of fear, aggression and thirst are triggered. We don’t know WHY, exactly, but this behavior many times stimulates rage and mindless violence in the animal. As the virus multiplies, it proceeds in certain facial nerves from the Brain Stem, down to the salivary glands, where it multiplies and is expressed in the animal’s saliva. It actually stimulates the salivary glands to produce this virus-laden “shedding” such that, as the animal bites other mammals, the virus enters a new victim, and begins the cycle again. So, it is NOT a blood-borne “parasite”. It’s not even a parasite….it’s a pathogen, and it WILL kill you if you don’t get treatment soon after a bite by a rabid animal. The good thing is that the VAST majority of human bites are committed by NON-Rabid animals. The Biting animal can be tested by a Clinical Veterinary Laboratory in your state. If the animal IS rabid, you can get 4 (FOUR) shots in the arms and a few around the site of the bite, and defeat the disease completely.

  • Roy Niles

    Good people like Clarence Thomas? Ouch.

  • cgosling

    Can this be the reason there are so many religious fanatics?

    • Szymon Gryg

      Perhaps a fungal infection. Like the Amazonian strain that infects the brains of certain ants and compels them to climb out of their normal habitat and die in the treetops, unwittingly spreading future generations the fungus over a larger area and to other ants… Fun to think about but more than likely, a belief in God is perhaps a genetic cognitive error, one that is later activated by an unidentified environmental trigger… probably a virus, fungus etc.

      • cgosling

        Interesting theory !

        • Szymon Gryg

          Wouldn’t it be fantastical if God were actually a parasite or a fungus… but we couldn’t see it because we are trapped behind our eyes, in that particular reality.

          The meat does the thinking.

  • gseattle

    Important note:

    Most everyone repeats the meme that toxo can’t hurt you unless sick or pregnant, not true at all. They say it is usually “asymptomatic”, meaning — no symptoms, supposedly. They aren’t thinking straight. What they meant to say is — no readily observable **physical** symptoms like sore throat, headache, cough, rash etc, i.e. Those are medical people, so they have blinders on, they ignore behavioral issues for the most part. Plus, the mindlessly repeated falsehood originated from observations of mice, not humans, in 2010. One can’t interview a mouse.

    Recent revelations from Toxoplasmosis studies regarding behavioral effects on humans — mind-boggling.

  • WeQqendi Walver

    How to determine if you have the feline parasite? is there any test for it?

  • Orange Guzzi

    1 teaspoon of turpentine for 6 days will eliminate the parasites. Take it from someone that has tried everything to eliminate them.

    Power these things have over the human brain is serious.

    Finding help in the U.S. is impossible.

  • Amanda Tucker

    I only have 1 simple question… How did an article about neurological parasites lead to a political debate?

  • aapaap

    Nothing too serious. If these parasites/pathogens became real threats, the human body would probably adapt to it, like all other animals do to survive. Most of the people infected will unfortunately die tho, but this is our fault as well. Our presence became too big on Earth, so that pathogens now can spread really fast.

  • harish kashyap

    so, can the situations in movies like QUARANTINE, TRAIN TO BUSAN ,
    QUARANTINE:TERMINAL ……….etc occur .

  • عمران محمد

    I have a dohter that infected with Toxoplazma wen i was pregnant and couse her real damages like lost three fingers in right hand and three in her both feet and hard Lerner in school. Can you help her please if there is any cure and i don’t know if thet parasite is stell there doing more damege. I am sorry i am from Afghanistan living in Saudi arabia that’s why my explaining is not that good.


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


See More

Collapse bottom bar