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Toxoplasma parasites a cause of schizophrenia?

I was reading today about a new study that shows that rats infected with toxoplasma parasites are “controlled” by the parasite to perform acts beneficial to it. Some of these acts are decidedly suicidal for the poor rat, unfortunately, like being attracted to the smell of cat urine.

Toxoplasma has two basic life stages: their sexual stage can only take place in a cat, the asexual part of their life can take place in any mammal. So, if Toxoplasma wants to reproduce, it needs to get inside a cat. With rats, it does this by short-circuiting a key rat survival instinct- the one that keeps them away from areas where cat urine can be smelled. The cat eats the infected rat, the parasite gets to have sex, and everyone is happy…well, except maybe for the rat.

The exact mechanisms that the toxoplasma gondii protozoa uses to achieve this result are not yet understood. It also isn’t determined yet whether the parasite has any real impact on adult humans who might happen to pick it up. It is known, however, that a pregnant woman who picks up the bacteria will have a higher probability of giving birth to a child with schizophrenia…along with other problems like hydrocephalus and spontaneous abortion.

Its also known that about 15% of people in the United States show signs of having been infected with Toxoplasma parasites…and about 50% of people world wide (88% in France…I wonder what the French are up to?). The question is: are some mental disorders in humans caused by this parasite? Is the legendary French arrogance simply a result of the parasite trying to get citizens of France eaten by giant cats? Science may one day soon answer this and other pressing questions…

Humour aside, the ability of a simple parasite to selectively alter deep-seated mental behaviors for its own benefit is intriguing to say the least.

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4 comments to Toxoplasma parasites a cause of schizophrenia?

  • Shane

    Forgive the format, I copy and pasted my comment from “word”.

    Interesting article, but I don’t think it really proved anything other than “some rats when infected by a certain virus, act a certain way.”

    I don’t consider myself an expert, but having lived with Schizophrenia in my family for over a decade, I do try to keep up with what is happening with the illness.

    There are as many different kinds of “Schizophrenia” as there are commond colds. “Schizophrenia”, for the most part is a catch all term, much like “irritable bowel syndrome”.
    I can see how having 1 type of “Schizophrenia” may cause you to act a certain way (in the case of the rats, they were attracted to cat urine). But that doesn’t mean that all rats that have Schizoprenia, will have the same type “Schizoprenia”. Unless the rats are infected with Toxoplasma gondii which “creates” 1 specific type of mental behaviour (or what the scientists keep wanting to call “Schizophrenia”).
    Schizophrenia can also be chemically induced for short or long terms in a variety of ways, lysergic acid diethylamide otherwise known as LSD for one, can cause short term (several hours) “Schizoprenic” episodes in people. So can psilocybin (active compound in magic mushrooms). And many other substances, both natural and man made.
    I found a few of the items in the article to be too general to be of any real information.

    —Toxoplasma infection is associated with damage to Astrocytes, glial cells which surround and support neurons. “Schizophrenia” is also associated with damage to astrocytes.

    In the case of patients with “Scizophrenia”, their Astrocytes do usually show up as being damaged. Unfortunately, many things are associated with damage to the Astrocytes. Any head trauma (concussion, bump on the head, stroke, loss of oxygen, even a heavy night of drinking) will produce damaged Astrocytes. Even too much or not enough of a certain Amino acid (glutamate I think?) can actually cause damage to Astrocytes, and eventually it will even kill you. So having damaged Astorcytes does not mean that you have Schizophrenia, but having Schizophrenia does mean you will have damaged Astrocytes. All of us have damaged Astrocytes, if not right this minute, we will by saturday night :).

    Scientists really still know next to nothing about Astrocytes. But it is good to see that they are trying to figure our brains out. The brain really is the “final frontier”, forget space šŸ™‚

    Having damaged Astrocytes being associated with Schizophrenia is kind of like associating a mole to lung cancer. Sure, a mole can possibly turn into cancer (BCC, SCC or Maignant Melanoma), which if not treated could turn into other forms of cancer and spread anywhere in the body (including the lungs), but does it mean that having a mole means that you will have lung cancer? No.

    –Pregnant women with high levels of antibodies to Toxoplasma gondii are more likely to give birth to children who will develop schizophrenia.

    According to the article, they say that about half the world population (3 billion) has Toxoplasma gondii, and if we aren’t schizophrenic because of it, then we must have anti-bodies to keep the infection at bay. So if half of the world is infected, and half of that number are women (roughly) then that would mean that approximately 1.5 billion women in the world are infected by Toxoplasma gondii. Also, probably accurate, now lets say 1/3 of them have children, that would mean about 500 million women would have a high chance of having a child with “Schizophrenia”. I just don’t buy it, that would be just too many cases, espcially since only 1% to 2% (about 60 million people) of the world has any form of Schizoprenia. The scientists definition of “high” must be a heck of a lot different than mine.

    –Human cells raised in petri dishes, and infected with Toxoplasma, will respond to drugs like haloperidol; the growth of the parasite stops. Haloperidol is an antipsychotic, used to treat schizophrenia.

    This bit of information is really sort of disturbing. Not because of the fact that Toxoplasma can be “halted” by Haloperidol, but disturbing, because I bet you if you put Halo-peridol in any type of petri dish, full of any kind of human cells, it would prevent growth of pretty much anything. Halo-peridol is a fairly powerful anti-psychotic, that not only can help with some people who have “Schizophrenia”, but can also cause all sorts of terrible things, stroke, coma, heart-attack, and cancer to name a few. I think this little bit of information was used in the study to try and bolster any claims that they were making. If they put hand soap a petri-dish with human cells that were infected, I bet the soap would halt the growth too, not to mention probably kill everything in the process. But does this mean that hand soap can cure “Schizophrenia”?.

    Any study with “Schizophrenia” is a positive in my mind. Or any studies done about the brain for that matter. Not nearly enough is known about the illness or the brain really. And it would be great if it was caused by 1 virus, or infection. But like I said earlier, there are so many different kinds, all with different ways that they effect the human brain. Hopefully science can cure the common cold someday, which by comparison to schizophrenia should be a cake walk, then maybe a “cure” for 1 particular type of schizophrenia can be found.

  • Shane

    I should really proof read before i post.

    Maignant Melanoma, should be “Malignant Melanoma”. Maignant Melanoma does sound bad though doesn’t it?

  • Fantastic response, Shane- and bang on. Most of what scientists know about the brain and behavior is tremendously vague. At best, this toxoplasma relationship to schizophrenia is just one clue among thousands, and could be a complete red herring.

    I find it more interesting, personally, that the parasite seems to be able to cause a specific behavior in rats (being attracted to cat urine odour) that is beneficial to itself and totally destructive to its host. Humans still have a hard time figuring out whether some behavior is physical /biological or learned, and yet some microscopic bug can make very specific stuff happen that our best science can’t explain.

    Your comments really put the study into perspective for me- Thanks!

    P.S.: regarding editing your comments- I *think* if you create an ID on this site (with a password and stuff), you can edit your own comments. The “default” way of creating comments isn’t really logging in- the site is sort of considering you to be “casual” if you just type your name and email.

  • Shane

    Ahh ok, will try the id thing. Thanks šŸ™‚

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