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  1. #1
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    Unlocking secrets of an obscure but powerful parasite

    On paper, Toxoplasma gondii looks as if it ought to be the most famous parasite on Earth. This single-celled pathogen infects more than half the world's population.

    Each of Toxoplasma's victims carries thousands of the parasites, many residing in the brain. And Toxoplasma is equally adept at infecting all other warm-blooded animals.

    Scientists are now discovering some of the secrets of Toxoplasma's success. Researchers in Sweden report that the parasite fans out through the body by manipulating mobile cells that are part of the immune system. Toxoplasma hijacks these so-called dendritic cells and makes them race around the body and ignore commands from other immune cells to commit suicide. The dendritic cells sneak the parasites into the brain and other defended organs, acting much like a Trojan horse.

    Strategies like this have made Toxoplasma incredibly widespread and incredibly obscure. Pathogens that infect far fewer people, like the Ebola and West Nile viruses, are more famous.

    Toxoplasma's obscurity is in fact a great tribute to its powers.

    "To the parasite's credit, it's incredibly successful," said Dr. Lloyd Kasper of Dartmouth University. "It's adapted itself to be a benign infection."

    For the vast majority of people, Toxoplasma causes no serious effects. It manages this feat by hijacking the body's cells and immune system, and establishing a careful harmony between parasite and host. "Once you get infected with Toxoplasma, you're infected for life," Kasper said.

    Toxoplasma can, however, cause serious brain damage in those with weak immune systems, like fetuses and adults with AIDS.

    Cats play a major role in the parasite's success. They can carry it in their intestines, where they can produce egglike cysts called oocysts. A single infected cat can shed 100 million oocysts in its droppings. The oocysts can survive in the soil for over a year and can contaminate drinking water.

    Oocysts can infect humans, as well as other mammals and birds. Undercooked pork, chicken and other meat is another route Toxoplasma can take into our bodies.

    Once Toxoplasma enters a host, it spreads quickly. Within hours it can be detected in the heart and other organs. It is even able to infect the brain, which is protected from most pathogens by a tight barrier.

    Antonio Barragan and his colleagues at the Swedish Institute for Infectious Disease Control and Karolinska Institute in Stockholm were puzzled at first about how Toxoplasma managed this swift journey.

    "When we looked for parasites in the blood, we found very few that were just swimming around," said Barragan, an associate professor. But the scientists observed many of the parasites inside immune cells known as dendritic cells.

    Barragan was intrigued. Dendritic cells, common in the gut, often come into contact with pathogens. They respond by crawling to the lymph nodes or the spleen, where they communicate with other immune cells.

    "That led us to think, what if this parasite is directing these cells to move and to disseminate through the body?" Barragan said. He and his colleagues put dendritic cells in a dish and injected them with Toxoplasma. They noticed that the parasites triggered a peculiar change: the dendritic cells became hyperactive, crawling for an entire day.

    Next, the scientists observed how Toxoplasma spread through a living animal. They added a firefly gene to the parasites so that they produced a glow. When they injected the parasites into mice, a little of the light escaped from the animals. By putting the mice in a darkened box, Barragan and his colleagues could track the parasites as they spread.

    Injecting dendritic cells carrying Toxoplasma spread the parasites to the brain and other organs far faster than injecting Toxoplasma alone. The researchers concluded that Toxoplasma was taking charge of the dendritic cells and riding along with them. Their results are published online in the journal Cellular Microbiology.

    As Toxoplasma spreads through the body, it invades cells. Unlike other pathogens, Toxoplasma can enter almost every type of cell in the bodies of thousands of host species.

    If Toxoplasma simply spread from cell to cell, it could cause serious harm. But killing its host is not in the parasite's best interests: Its goal is to get into its final host, cats, the only creature in which Toxoplasma can reproduce by making oocysts that are shed in feces. Instead, Toxoplasma has evolved to be extremely contagious, but not very harmful. "This is an organism that has very cleverly worked out a way to go from one host to another," said Alan Sher, chief of the Laboratory of Parasitic Diseases at the National Institutes of Health.

    Toxoplasma becomes a menace when it does not have a healthy immune system to control. Pregnant women infected for the first time by Toxoplasma may pass it to their unborn children. Without a strong immune system to keep the parasite in check, a fetus can suffer massive brain damage. Toxoplasma is also dangerous to adults with weakened immune systems. A quiet Toxoplasma infection can suddenly explode.

    For decades, most scientists believed that people with healthy immune systems had no effects from Toxoplasma. But some studies in recent years have hinted that the parasite can exert surprising effects on behavior, at least in animals.

    In 2000, British scientists demonstrated that rats infected with Toxoplasma lost their fear of cats. They proposed that this strategy increased the parasite's chances of getting into its final host.

    Scientists at Stanford University recently followed up on these experiments, studying rats and mice. "They actually show a mild attraction to the cat odor," said Ajai Vyas, a Stanford neurobiologist. "It's not just the loss of an old behavior. A new behavior is being induced."

    Vyas and his colleagues found that Toxoplasma's effects were precisely aimed at cat odor. The rats were still afraid of dog odor but not of rabbit odor. They could also acquire new fearful responses. "Only the innate fear to the cat was different, which was very surprising," he said.

    How Toxoplasma incites this change is a mystery. It is possible that the parasite alters the production of certain neurotransmitters. "But I don't know how some global change could have such a specific effect," Vyas said. He reported his results in May at the annual meeting of the International Behavioral Neuroscience Society.

    Some scientists suspect Toxoplasma may influence the human brain. Several studies suggest a correlation between Toxoplasma and schizophrenia, but the claims for a connection are not widely accepted.

    Dr. Robert Yolken, the director of the Stanley Laboratory at Johns Hopkins University, and his colleagues reviewed military medical records. They found that soldiers who developed schizophrenia were twice as likely as other soldiers to show signs of Toxoplasma infection.

    Toxoplasma's dangers, both proven and potential, are cause for concern, experts say. "It's a substantial public health risk," Sibley said.

    Dr. Milton McAllister, a veterinary parasitologist at the University of Illinois at Chicago, has called for controlling the spread of Toxoplasma by cats. He notes that oocysts from cats can also infect wildlife. Toxoplasma has even been detected in sea otters, suggesting it can reach the ocean.

  2. #2
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    Re: Unlocking secrets of an obscure but powerful parasite

    another secret menace that would threaten the pillars of science and medicine if the PUBLIC was aware.and it's not sexual related so no HUSH!HUSH!needed?demand a trillion dollars and threaten to drop leaflets from planes!?or better yet,develope a test(expensive i'm sure) for cats and sell it to vets!!70 million cat owners paid willingly,only to be informed.....your cat has to DIE!?forget iraq.....the economy.....taxes....hehe!!next US pres candidate says to voting public....i will do everything necessary to save your cat!!hehe!!
    Last edited by lexx; 06-22-2006 at 08:32 AM.

  3. #3
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    Re: Unlocking secrets of an obscure but powerful parasite

    What an intriguing parasite. If you have never seen the documentary "The body snatchers" then i thoroughly recommend you do.
    http://www.abc.net.au/tv/guide/netw/...005T203000.htm

    I think i saw it on discovery channel though, so I hope thats the same one. Anyway, its a whole documentary about parasites which live in and on our bodies, and how some of them can actually manipulate us and our bodies etc. Really itchy stuff.

    i also found this while looking for that: http://news.bbc.co.uk/2/hi/health/3287733.stm

    The link mentioned between Toxoplasma and Schizophrenia is interesting. I would like to see that research fully developed... I think a parasitic infection being the cause of schizophrenia would make a lot of sense. (particularly after you watch that body snatchers doco)

    Shane

  4. #4
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    Re: Unlocking secrets of an obscure but powerful parasite

    Quote Originally Posted by aegist
    What an intriguing parasite. If you have never seen the documentary "The body snatchers"
    Cool I'm downloading it now :)

  5. #5
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    Re: Unlocking secrets of an obscure but powerful parasite

    how where?

  6. #6
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    Re: Unlocking secrets of an obscure but powerful parasite

    How very interesting?
    Maybe the BBC licence fee does have some benefits.
    It seems that 80% of the French population are infected with Toxoplasma, due to their addiction to undercooked meat.
    Might explain the strange behaviour of the froggies (only joking)

  7. #7
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    Re: Unlocking secrets of an obscure but powerful parasite

    Quote Originally Posted by SubJunk
    Some scientists suspect Toxoplasma may influence the human brain. Several studies suggest a correlation between Toxoplasma and schizophrenia, but the claims for a connection are not widely accepted.

    Dr. Robert Yolken, the director of the Stanley Laboratory at Johns Hopkins University, and his colleagues reviewed military medical records. They found that soldiers who developed schizophrenia were twice as likely as other soldiers to show signs of Toxoplasma infection.

    Toxoplasma dangers, both proven and potential, are cause for concern, experts say. "It's a substantial public health risk," Sibley said.
    Quote Originally Posted by aegist
    The link mentioned between Toxoplasma and Schizophrenia is interesting. I would like to see that research fully developed... I think a parasitic infection being the cause of schizophrenia would make a lot of sense. (particularly after you watch that body snatchers doco)

    Shane
    All good stuff. I remember seeing info on Toxoplasma from a long time ago. It was suspected that it was likely transmitted by contact with cat feces and children were especially likely to pick it up. Not much was known about Toxoplasma at that time.
    Toxoplasmosis was the term used then to describe certain known problems associated with Toxoplasma.
    The possible link to Schizophrenia and a myriad of chronic problems is especially interesting. I remember also seeing theories that Schizophrenia may also be an auto immune syndrome of the hypothalamus. It was discovered in autopsies that the hypothalamus of patients with Schizophrenia had severely deformed cell tissue structure
    Since Toxoplasma can infect both the brain and the immune cells there could be some new discoveries if this is researched more completely.

  8. #8
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    Re: Unlocking secrets of an obscure but powerful parasite

    Quote Originally Posted by peasant
    How very interesting?
    Maybe the BBC licence fee does have some benefits.
    It seems that 80% of the French population are infected with Toxoplasma, due to their addiction to undercooked meat.
    Might explain the strange behaviour of the froggies (only joking)
    And the "strange behavior" in the House of Lords might be explained by inbreeding...

    Can you give me a 'merdre'

    "merdre!"

    All my homies say "merdre"

    "merdre"

    Papa Ubu say "merdre"

    "merdre"

  9. #9
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    Re: Unlocking secrets of an obscure but powerful parasite

    Quote Originally Posted by Phinnly Slash Buster
    All good stuff. I remember seeing info on Toxoplasma from a long time ago. It was suspected that it was likely transmitted by contact with cat feces and children were especially likely to pick it up. Not much was known about Toxoplasma at that time.
    Toxoplasmosis was the term used then to describe certain known problems associated with Toxoplasma.
    The possible link to Schizophrenia and a myriad of chronic problems is especially interesting. I remember also seeing theories that Schizophrenia may also be an auto immune syndrome of the hypothalamus. It was discovered in autopsies that the hypothalamus of patients with Schizophrenia had severely deformed cell tissue structure
    Since Toxoplasma can infect both the brain and the immune cells there could be some new discoveries if this is researched more completely.
    WTF is your POINT!?i used to respect your opinion but of late i think u you have gone to the DOGS!?of war or straw or whatever!?a DESCENT/into hell!? due to ANTI religious DOCTRINE in ANY form!?hehe!!just askin!?did you like/appreciate "vanilla sky"!?or "fight club"!?hehe!!your way to scientifically OPTOMISTIC!?in rejection to/incompliance with/in social POSITION with/OOPS!! i forgot!!I LOVE YOU MAN!!hehe!!.....on with the SHOW!?.....
    Last edited by lexx; 07-03-2006 at 07:44 AM.

  10. #10
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    Re: Unlocking secrets of an obscure but powerful parasite

    LOL, i thought lexx was angry at the beginning, then I thought he was just joking...then I realised I was just confused again...
    :(

  11. #11
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    Re: Unlocking secrets of an obscure but powerful parasite

    Which reminds me:
    Quote Originally Posted by SubJunk
    Cool I'm downloading it now :)
    Did you end up watching that doco?

  12. #12
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    Re: Unlocking secrets of an obscure but powerful parasite

    Quote Originally Posted by aegist
    Which reminds me:

    Did you end up watching that doco?
    It's in the queue :) I have a lot of things to download, hundreds of things

  13. #13
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    Re: Unlocking secrets of an obscure but powerful parasite

    Quote Originally Posted by aegist
    LOL, i thought lexx was angry at the beginning, then I thought he was just joking...then I realised I was just confused again...
    :(
    if you are confused......then i am confused!?that is the EQATION of eqality is it not!?you Do believe in the EQUALITY(possiblity)of MAN!?hehe!!take the iniquity of the bible FOR instance......any idea what that means!?but as to your SUPPOSITION!?is it the supposition of the MASSES!?the sucker born every minute of (P.T.BARNUM!?)are you here proving your ALLEGIENCE to the RAPING of SAME due to BIBLICAL FORCAST!?or am i to asume you are just begging to be ENLIGHTENED by my WORDS!?hehe!!just askin MR. WISE GUY!!(ME!?)hehe!!but any way.....I LOVE YOU like a BROTHER!!so dont pull no S H I T!!the LEXX has NO FREINDS!?(only lovers!?).......just askin.....hehe!!......
    Last edited by lexx; 07-03-2006 at 08:43 AM.

  14. #14
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    Re: Unlocking secrets of an obscure but powerful parasite

    Quote Originally Posted by aegist
    What an intriguing parasite. If you have never seen the documentary "The body snatchers" then i thoroughly recommend you do.
    http://www.abc.net.au/tv/guide/netw/...005T203000.htm

    I think i saw it on discovery channel though, so I hope thats the same one. Anyway, its a whole documentary about parasites which live in and on our bodies, and how some of them can actually manipulate us and our bodies etc. Really itchy stuff.

    i also found this while looking for that: http://news.bbc.co.uk/2/hi/health/3287733.stm

    The link mentioned between Toxoplasma and Schizophrenia is interesting. I would like to see that research fully developed... I think a parasitic infection being the cause of schizophrenia would make a lot of sense. (particularly after you watch that body snatchers doco)

    Shane
    i recall that there were 2 movies made about the "body snatchers",and i saw them both!!hehe!!now the funny thing is,the snatchers represented a calm,peaceful,we all get along state of mind!?and that THIS was PRESENTED as TOTALLY ALIEN!?GO FIGURE!?hehe!!.......just askin......

  15. #15
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    Re: Unlocking secrets of an obscure but powerful parasite

    Yeah, it was hard to find information on the documentary for all of the information out there on the movies. I hope SubJunk is downlaoding the correct thing :)

  16. #16
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    Re: Unlocking secrets of an obscure but powerful parasite

    Quote Originally Posted by aegist
    Yeah, it was hard to find information on the documentary for all of the information out there on the movies. I hope SubJunk is downlaoding the correct thing :)
    well ,i guess for your SAKE!?(saki)there "IS" a correct thang!?hehe!!just askin.....the LEXX is NEVER WRONG!?god is god and the rest is.....history!?just askin.....no intimidation IMPLIED!?come together ,right now,over me!?no way bukake man!?hehe!!.......
    Last edited by lexx; 07-03-2006 at 09:14 AM.

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