Above is a ~20 minute (absolutely worth every minute) interview with the leading researcher, Dr. Robert Sapolsky, in the study of Toxoplasma & its effects on humans. This is a must see. [click here to read the full text of the interview]
“…this is a protozoan parasite that knows more about the neurobiology of anxiety and fear than 25,000 neuroscientists standing on each other’s shoulders…” – Dr. Robert Sapolsky
Toxoplasma (Toxoplasma gondii) [Toxo] was first observed in 1908. You may have heard of it as the crazy parasite that makes rats attracted to cats. This, in its own right, is astonishing, interesting, & bizarre. It has also been widely known that pregnant women should stay clear of cat scat & other sources for Toxo as it can adversely affect the development of the fetus.
Dr. Robert Sopalsky at Stanford has taken this link to humans further & has been studying, in detail, how it is affecting humans with some startling observations, but we’ll get to that later.
Dr. Sapolsky, Professor of Neurology and Neurological Sciences, is known for his work studying the biological effects that stress has on primates, including humans. In addition to his research at Stanford, he annually spends time in Kenya as a research associate at the National Museums of Kenya researching the effects of stress on a population of baboons for well over 20 years. His research has lead to hundreds of scientific publications & six books including the acclaimed Why Zebras Don’t Get Ulcers, Monkeyluv: And Other Essays on Our Lives as Animals, A Primate’s Memoir: A Neuroscientist’s Unconventional Life Among the Baboons, and others
Toxo Life Cycle (click for high res)
In order to understand how it affects humans, one must first understand how it affects its desired hosts: cats and rodents.
“Toxo knows how to hijack the sexual reward pathway.” – Dr. Sapolsky
For a parasitic protozoa it has a remarkably complicated and fascinating life cycle. The quick summary is that Toxo can only sexually reproduce in the gut of a cat. The cat then excretes Toxo in its feces which is then consumed by the intermediate hosts (e.g., a rat). Once in the rat Toxo’s goal is to then be eaten by a cat so it can be fruitful and multiply, but as I mentioned, this can only take place in the cat’s gut. Toxo’s goal is to get the rat eaten by a cat.
Toxo could get the desired effect through a whole sort of seemingly obvious ways; e.g., Make the rat hard to run so it is easier for a cat to catch it. Instead it takes a far more interesting approach:
Toxo generates cysts in the brain of the rat. These cysts take over the fear center of the brain, but specifically the fear of predators. Common fear sources for rodents (e.g., bright lights, open spaces, etc.) still operate perfectly well in an infected rat, but now they are no longer afraid of cat piss.
That alone would be cool enough, but Toxo takes it one step further. When Toxo is going about futzing with the fear center of the brain it also goes into the sexual excitement part of the brain. It hijacks the incoming Fear of Cat Piss™ and instead diverts the signal to the Barry White™ center of the brain.
“Somehow, this damn parasite knows how to make cat urine smell sexually arousing to rodents, and they go and check it out. Totally amazing.” – Dr. Sapolsky
The rat is now sexually attracted to cat piss!
(This is a fetish that gets you eaten by your predator and rats clearly do not have any safe words with cats.)
On top of all this, Toxo apparently has been hanging out in hipster bar bathrooms doing lines of blow off of some cat’s ass. The parasite has the mammalian gene for creating dopamine (which I have discussed in brevity previously):
“Cocaine works on the dopamine system, all sorts of other euphoriants do. Dopamine is about pleasure, attraction and anticipation. And the Toxo genome has the mammalian gene for making the stuff. It’s got a little tail on the gene that targets, specifies, that when this is turned into the actual enzyme, it gets secreted out of the Toxo and into neurons. This parasite doesn’t need to learn how to make neurons act as if they are pleasurably anticipatory; it takes over the brain chemistry of it all on its own.” -Dr. Sapolsky
This is all good fun for fucking with the behavior of rat brains, but is there anything that crosses over into the human realm? This is the question that Dr. Sapolsky’s team has been working on.
“What does Toxo do to humans? And there’s some interesting stuff there that’s reminiscent of what’s going on in rodents.” – Dr. Sapolsky
It seems that humans aren’t having love affairs with cat piss. Instead, it appears that humans are having the fear center of their brain circuit bent causing some interesting findings.
“A small literature is coming out now reporting neuropsychological testing on men who are Toxo-infected, showing that they get a little bit impulsive. … And then the truly astonishing thing: two different groups independently have reported that people who are Toxo-infected have three to four times the likelihood of being killed in car accidents involving reckless speeding.” – Dr. Sapolsky
In a very specific example, Dr. Sapolsky goes on to state that motorcyclists have a high probability of being infected with Toxo. I wonder if my friends who have a love for motorcycles grew up with cats and therefore had a higher probability of being exposed.
“…if you ever get organs from a motorcycle accident death, check the organs for Toxo. I don’t know why, but you find a lot of Toxo.” – Dr. Sapolksy
It is stunning that human behavior is being modified by a parasite that wasn’t even intended for humans (“off label use” perhaps?). This appears to be pure happenstance.
I am left wondering, “What if there is a parasite out there that specifically uses humans as their hosts?”
If a simple organism can make such precise modifications to a rat’s brain, it is not far fetched to think that this is already going on inside our heads on a far larger scale. It would appear to me that we have only scratched the surface.
It appears that we are far more affected by our surroundings, things we ingest, exposure to compounds, (e.g.,Epigenetics) and now parasites than many originally thought. Our DNA appears to be the hand we are dealt, but how those cards are played seem to be under the control of far more players than many had originally assumed.
I have some sideline questions I would love to have answered:
•How do you test for toxo?
(I would love to be able to find out if I have any in my system, for example.)
•How does one test for dopamine activity in the brain without resorting to trepanation?
For those interested in more of Dr. Sapolsky’s works, which I highly recomend, here is a video of a talk he gave at Stanford last year about “The Uniqueness of Humans“. It is an absolutely wonderful talk that equally knocks us down a peg or two at the same time it rises us like a yeasty bread such that the pegs that are missing are now merely holes to push tasty cream cheese into.
{ 52 comments… read them below or add one }
As a motorcyclist who grew up with cats I'd be very interested in being tested also.
Very interesting.
Great article, there is a correlation between Cat Ladies and toxo as well as schizophrenia. All the correlations are interesting I cant wait for definitive science to aris eon this subject.
Some people have said that the effects on humans are coincidental, as the parasite is really only interested in spreading itself through cats and rats. Perhaps this is wrong. If the parasite can make rats attracted to cats, then perhaps it can do the same for humans. On the face of it, there would be no evolutionary advantage for it to infect humans, as this is a reproductive dead end for it. But what if this infection made infected humans like cats? By improving the survival of cats, the parasite would have more cat hosts to infect and reproduce in. If the number of extra toxo parasites arising from this exceeded the number wasted by infecting humans and so not being able to reproduce, then there would be an evolutionary advantage to this behaviour. The genes promoting it would spread through the population and be passed on to later generations in increasing numbers. It's basically turning the argument around. Instead of people having toxo infection because we have cats, it could be that we have cats because we have toxo infection. Could this explain why humans like cats? Can anyone suggest any experiments that could test this hypothesis?
Easy to test for toxo. You have a test called a toxoplasma IgG drawn. If this antibody level is elevated, you were infected with toxo at some point in the past.
In Palo Alto, there is the Toxoplasma Serology Laboratory and I think IGeneX Lab does the test as well.
Here is info from UCSF – http://www.ucsfhealth.org/adult/adam/data/003514….
Many thanks!
I'm mobile at the moment, but I'm getting a lot of great feedback and leads. I'll probably write a follow up. Going to check out your links later.
Again, thank you!
I would love for our physicians at large to know to test for Toxo when potential indicators arise.
As I discovered with my experience with excessive cases of Strep (Groups A, B, C and G, I believe), the "rare" types of Strep are only rare because we only test for Strep Group A (rapid in-house culture tests done with swap kits). Just because we don't see it doesn't mean it isn't out there.
E.g., If someone shows a greater amount of reckless driving than normal, why not test them for Toxo?
If nothing else, we'd all benefit from a wider breadth of scientific data.
And then? Can it be treated in humans?
My current understanding is that, no, you can’t. Once the cysts are in your brain they are propogated enough that, as far as I can tell, you wouldn’t want a scalpel in there without a far better reason.
That isn’t to say nothing exists; I will have to do more research. It seems that Toxo in humans is in the early stages of research and we will be getting more data as time goes by.
If you do find anything out there, please do share!
The cysts occur on the brain-side of the blood-brain barrier as I recall my parasitologist pal telling me. That means drugs aren’t getting to it.
“Easy to do” and cheap or covered by health insurance are two different things.
If it has a very easy access level, I think it would be an easy sell to get motorcyclists to go in for testing. It would probably be a very fine data point for anyone to have and would welcome it into our standard testing regime.
But as a famous rapper once said, “mo’ data, mo’ problems’,” right??
The “Cat Ladies” and “Schizo” correlation is interesting, but not as interesting as the other aspects of what might be going on.
As is always the case, it seems, “more data needed” is the case.
I also grew up around a lot of cats, but I absolutely hate motorcycles… on the other hand my younger brother loved them.
you probably have toxo 🙂 the proof is in the margins. hope you can preserve the staring cats synchronizing with the sapolsky video 🙂
Completely unplanned and happenstance! Hilarious nonetheless.
I work in pediatric infectious disease, and I’ve worked up several kids for Toxo infection. Toxo can be treated, but generally doesn’t need to be. The meds have side effects and need to be taken for months. In some parts of the world a large proportion of the population are infected and apparently do just fine. It can cause problems in immunosuppressed people (HIV specifically) and in babies in the womb, when the eye and brain damage can be quite nasty.
Other things of interest: men specifically get stupid. Women tend to become more gregarious and attractive.
The Palo Alto lab is the world’s best at diagnosing Toxo, and is able to fine-tune the timing of infection using avidity testing of the antibodies (so they can say whether the infection occurred within a few months, which can be helpful for managing pregnant women). The guy who runs the lab, Jack Remington, invented the test known as “The Remington test”.
Thank you very much Bennett.
Do you by chance have any URLs to share?
At some point I will most likely have to do a follow up to this based off of all the comments. Please feel free to send any data my way.
Sounds like fun, do I have to eat the cat crap?
You don't have to, but I think you should. Make sure to make a video of it!
(My understanding is that just accidentally getting some into your food in any manner can get the microscopic parasite into you properly. Even touching something that was in contact with cat scat and then touching something that goes into your mouth could probably be a viable transmission.)
I am merely making the assumption that few out there actually eat cat crap instead of a candy bar.
I am left wondering, “What if there is a parasite out there that specifically uses humans as their hosts?”
Herpes. The “sleeping sickness” spirochete. Syphilis. Oh, you want multi-cellular parasites? How about religion? Scientology is surely a disease. So is pentecostal Christianity.
On another note, I remember reading that something like 50% of the human population of Brazil is infected with toxoplasmosis. Anybody have a referense?
Thank you Bob. I am left with only a smidgen of slack to smoke.
I'm more curious about parasites that use us as hosts, but then modify our behavior in interesting ways. (Scientology definitely does that, but I like me some clams.)
Syphilis is a no brainer (yes, pun intended). It doesn't really affect our brains to make use want to throw away condoms to perpetuate itself…unless I've missed some good articles. Then again, getting humans to want to have sex without protection is akin to getting hookers to NOT smoke crack.
We are pretty much hard wired already with all the things that STDs need to be fruitful and multiply. They are just taking the easy way by piggy backing on our absolute lust for lust.
Now if there were an STD that only could be transferred from something that can only live, say, on the latex of a condom, then I'd be impressed.
Filarial worms have high host specificity, so filarial diseases such as elephantiasis, loiasis (eyeball worm) and guinea worm infection could be considered human specific. Malaria is actually quite human specific and leprosy is confined to humans and armadillos.
And yes, malaria and toxoplasmosis are caused by related organisms – Apicomplexa. An old group of protists which have all taken up parasitic lifestyles. This group includes Cryptosporidium, a parasite found in poorly managed municipal water systems which also tends to cause severe illness in the immunocompromised.
@Bob: Brazil has high seroprevalence rates, with a random screening indicating 70% prior infection rates amongst women of childbearing years. (Rey, Luis, and Isabel Ramalho, “Seroprevalence of toxoplasmosis in Fortaleza, Ceara, Brazil” Journal of the Sao Paulo Institute of Tropical Medicine (May 1999)).
In addition:
~15-20% of the US population has antibodies (Jones et al., “Toxoplasma gondii Infection in the United States, 1999-2000,” Emerg Infect Dis (November 2003)), while France and Greece have previous infection rates of ~55% (cited in Cook et al, “Sources of toxoplasma infection in pregnant women: European multicentre case-control study,” BMJ, (15 July 2000)).
Eastern Europe appears to have comparable rates, with a nonrandom sample in southeastern Romania indicating urban female seroprevalence of 48.1% and rural female seroprevalence of 70% (Olariu et al, “Prevalence of toxoplasma gondii antibodies among women of childbearing age in Timis County,” Scientific Papers in Veterinary Medicine (Timisoara, Romania) (2008)). Without adding more citations, Asia and Africa also report high seroprevalence.
Thanks a ton for the data! Much appreciated.
Any chance you have any reference URLs?
Ongoing pharmaceutical research:
Discovery shows promise as a new treatment for toxoplasmosis (2003)
http://www.innovations-report.com/html/reports/me…
Newly Developed Anti-Malarial Medicine Treats Toxoplasmosis: (2008) http://www.newswise.com/articles/newly-developed-…
Treatment of toxoplasmic lymphadenitis with co-trimoxazole: double-blind, randomized clinical trial: (2010) http://www.ncbi.nlm.nih.gov/pubmed/20194044
I have heard that Toxo has some resemblance to Malaria. If this is the case, then the anti-malaria attack makes a lot of sense.
I first heard about Toxoplasma effecting human behavior in a book by Scott Westerfeld called Peeps(2005). Amongst this rollicking good fiction are scattered factual pages about parasites that add weight to the story. If you like fast well told grabs about the fascinating world of parasites, it's a must read.
http://scottwesterfeld.com/blog/books/peeps/
Someone should issue the book such that you can lick certain pages to get Toxo…
…like blotter in the pages of a Timothy Leary paper.
…but I digress.
Cute summary of the neurobiology of Toxo, but Sapolsky neglects to mention that tyrosine hydroxylase (the dopamine synthesis enzyme) is present in many organisms outside mammals. First off there are lots of invertebrate animals who use dopamine in their nervous systems and secondly, tyrosine hydroxylase has lots of other functions like cross linking the cuticle of newly molted insects or defending against pathogens. This is more an example of convergent evolution where another species has likely duplicated an existing TH encoding gene and adapted to produce dopamine.
Thank you very much for the enlightenment. Do you by chance have any links about non-mammalian dopamine use?
With all the comments coming in of interesting data, I think I'll probably have to write up yet another layman summary including all of the new or differing data.
lots of research on the effects of dopamine in Drosophila. Even sea urchin larvae have dopaminergic neurons (presumably to control swimming and muscular contraction of the stomach?) Check out the Wikipedia entry on dopamine – there’s dopamine in bananas! yum…
A science fiction story that explores the topic of mind-altering parasites in humans (and which mentions Toxo in passing):
http://www.davidwgoldman.com/Invasion_of_the_Patt…
As a woman who has serious eye damage from toxo, I’m very interested in these articles as they are published. The studies so far have shown very different reactions in men vs. women with toxo, and it makes me wonder what else this parasite might be responsible for.
I thought the eye damage “toxo” was toxocara, not toxoplasma.
From the, clearly, all knowing Wikipedia:
"…Rarely, a patient with a fully functioning immune system may develop eye damage or nasal lesions from toxoplasmosis…"
That being said, it could be a mix up. ToxoEye might indeed be a rare case of Toxoplasmosis causing eye damage either by immune disorder or by Chorioretinitis.
(Again, The All Knowing Wikipedia on chorioretinitis lists Toxoplasmosis as a potential cause.
My father and uncle both have suffered from toxo. It can attack nearly any organ in the body; in my father's case, it attacked his eye. Unfortunately the only treatment in the 1980's for toxo involved heavy doses of steroids; the effectiveness was marginal at best as he still lost approximately 80% of his vision in one eye and about 25% in the other. The steroids caused a lot of other problems which have shown up for the past three decades.
Before my grandmother passed away about ten years, it was understood in my family not to let her know that she had indeed passed the disease along during pregnancy.
I'm quite sad to hear of this. My condolences.
Was this clearly due to an exposure to cats?
The crazy thing is that Dr. Sapolsky discusses in his other talks that the over use of steroids can severely damage the brain. Specifically, it seems that steroids weaken neurons such that if they are bombarded by another "event", they are much more easily destroyed.
Google Video of his talk; it's about an hour and is one of his more scientific lectures for students rather than his layman discussions:
'Stress, Neurodegeneration and Individual Differences' by Robert Sapolsky
runtime: 1:19:36
10/10/2001 The Grass Traveling Sceintist Program presents Dr. Robert M. Sapolsky of Stanford University's Dept. of Biological Sciences in a seminar sponsored by the Dept. of VCAPP and the Northern Rocky Mtn. Chapter of the Society for Neuroscience.
So what does toxo do to cat brains?
That is a very good question.
As far as I can tell, and I am only an "interested party" not a specialist, is that it forms cysts in the brains of all mammals in a similar fashion. That being said, I don't think anyone has mentioned what you are probably getting at: What behavior differences might arise in cats?
I'd love to find out more!
Toxoplasmosis can cause a rip-roaring brain infection and death in cats. It can also cause liver disease but most of the time it is a transient infection of the intestines.
Very interesting!! I have active Toxo in my eye, just got over my latest infection. And I have a thing for travelling to dangerous countries on my own… not sure if they’re related. I certainly don’t drive cars fast. I’ve written my view on this on my blog. I’m going to start writing more on the subject as it bothers me to have a condition, and know so little about it.
I’d like to see more evidence of the motorcyclist-toxoplasmosis link before I go out and get tested…
I have tested positive for a current infection of Toxo (both IgM & IgG antibodies measured in large quantities).
My symptoms were a very severe 6 weeks of muscle aches, joint aches, fatigue, and even shortness of breath. The most debilitating aspect of Toxo was a sense of Depression. As the other symptoms have gone away, so has the Depression.
I am quite interested in whether this was related to Dopamine production or from the fact I was bed-ridden and unable to exercise.
I forgot to mention above that my lymphnodes in the neck and armpits were very swollen and painful throughout the 6 weeks.
Also, I had no direct contact with any cats.
Yoosdef, are so very close to the factual information. A parasite is the original hacker and has gotten itself into the build of the human and other animals, or in the dna it has set itself to be built in the womb and infused into the host and can appear like simple brain tissue. It is more a leader of the bacteria world and is chemical, plauges and such. It uses the human communications to spread its instructions to the parasites in other people and also uses the same books, to tell the human it’s so called place. You’ll find many illogical statements in religions and it is wrapped around instructions of care or disorder of the host for the parasite to do. Or hybridization. It puts its same instructions in childrens cartoons for the ones who are new and anywhere that is communicable, but it’s system of worship is for its own faster regeneration and can peruse humans to further its goals. Both being the voices of evil and good more known as schizophrenia, but it hides and indirect communication is chemical and direct is literally auditory hallucinations. If it can’t get other hosts to cause trauma for the younger people it will do it itself within the mind. It tries to take the place as the natural instincts of all beings to be the only ones with foresight into the future and distracts the human from using it’s own instincts and they never run from earthquakes or tsunamis as animals do. It has pulled the life of its’ host into itself and removing it will cause the death of the host, but those that are used in its show are more a carrier and it gives up its life to further its whole aims. For the human who are eaiser hacked, sexual disorders to breed in the traits where the parasite is stronger and host weaker. But now it is almost time for the reverse, and “the voices”, will be the television, radio, and the computer extension of the brain, they are already making it past the inflammatory responses and immune system but their attacks must be used wisely lest the hosts immune system attack them. These are the divisions it uses to incite them against one another of their beliefs and world views and typic mispelling as pure accidental. Though it may seem smart, it has no physical survival and blind men read the bumps on the log, its knowledge is a consistent furthering of what the human that is used as its instrument to see the world around it is the one now growing weaker of that the parasite, lord of the flies and creator of plauges, mostly an exaggeration to appear larger, object may appear closer than they are behind you. The balance system is almost fulfilled now, hence the parasite will be the “power” of the future, one with a negative terminal and one with a positive terminal and it will charge the houses and generate electricity; but what of its future, 11 one on the high end and one on the low end, it must live in its own delusion online and will be removed one day, and stuffed into the commodity boxes for resale, and 10 will be forbidden access to the human brain system, what of the words to be a more structered solidification of atomic and smaller worlds as they harden, and even down to yatto, where the buffalo roams and the seminole blows, they will all join in…
In examples 1–3, the second sentence is simply reordered.It is a good idea to make most if not all of the changes suggested.
Because these proportions will vary according to the sampling criteria rather than with the prevalence in the general population, they have no inherent epidemiological interpretation and they cannot be compared between studies (www2).The topics are extremely varied and include comments on previous publications and news items, warnings about the safe disposal of old equipment, and the applicability of new treatment methods.
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If I just happened to be a student in a field in any way related to this subject, I would be very happy to prove/disprove the following theory:
[There is a relation between Toxo <—> people in the SM/BDSM scene.]
Sure, after seeing this video it might be an open door to suggest a link between a girl saying "strangle me and I get wet" and the urine attracted rat, but that doesn't mean it couldn't be true, right? So, is there any data which proves/disproves some correlation between toxo and people getting exited by pain/fear? If not, shouldn't there be?
Just pitch a tent at the Wasteland entrance and swipe anyone who enters. If they ask "will it hurt?", just remember to say "yes!" 😉 I'd be thrilled to see the results.
My own very unscientific, much-to-small-sample of asking "were there cats around when you were born?" to people I know in the kinky scene just happens to get all "yes" answers, on top of which most girls also just happen to own cats now. Surely this is not the same as testing for toxo, since one might have cats but no toxo, or have toxo but no cats, but sometimes I forget my toxo-detection-kit… sorry!
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i'm surprised they don't ask toxo infected people if they like cats, or if they're interested in petting tigers and getting eaten by them or something. take a human that likes dogs, infect em with toxo, and then when they start liking cats, you got your answer. the moral of this story is: cats > dogs.
I think it's the best piece I have read about this subject thanks for sharing
I work in pediatric infectious disease, and I've worked up several kids for Toxo infection. Toxo can be treated, but generally doesn't need to be. The meds have side effects and need to be taken for months. In some parts of the world a large proportion of the population are infected and apparently do just fine. It can cause problems in immunosuppressed people (HIV specifically) and in babies in the womb, when the eye and brain damage can be quite nasty.
Other things of interest: men specifically get stupid. Women tend to become more gregarious and attractive.
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