cats and undercooked meat =

[khmerhit]

courtesy daily mail--

Is your cat making you crazy? Feline parasite 'can cause schizophrenia in humans'
Toxoplasma microbe 'takes over' the human brain

A person will become less risk-averse
Part of 'circle of life' for parasite

By Charles Walford
UPDATED: 16:41 GMT, 10 February 2012
Comments (28) Share
Jaroslav Flegr beleives that he has been infected by a parasite that is manipulating his behaviour
Parasites passed from cats could be causing schizophrenia in their owners, a scientist has claimed.
Jaroslav Flegr says has come to the conclusion because he himself believes he is a living example.
He says he has been infected by the parasite and it has altered his behaviour over a period of time.
The parasite, which is excreted by cats in their feces, is called Toxoplasma gondii and is the microbe that causes toxoplasmosis - the reason pregnant women are told to avoid cats’ litter boxes.
Since the 1920s, doctors have recognised that a woman who becomes infected during pregnancy can transmit the disease to the foetus, resulting in severe brain damage in the baby - or even death.
In adults the diesease causes flu-like symptoms - and those with a suppressed immune system can become seriously ill with complications such as encephalitis (inflammation of the brain) - but many carrying the latent disease and appear to have no symptoms.
However, once inside an animal or human host, the parasite then needs to get back into the cat, as that is the only place where it can sexually reproduce.
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And this, Flegr believes, is why the infection is making subtle changes to the human brain to manipulate the host's behavior - though he admits to being unsure how the parasite intends to use humans to this end.
But from his own experience the Czech scientist, 63, claims that over the past two decades his personality has been changing, leading him to behave in strange, often self-destructive ways.
The Toxoplasma gondii parasite is only able to reproduce in a cat's gut
'I wondered what was wrong with myself, ' he told the Atlantic.

Flegr recently told the magazine how he started thinking about his own theory almost 30 years ago after reading a book by the British evolutionary biologist Richard Dawkins.

The book described how flatworms, to help spread the species, are able to take over an ant's body by infecting their nervous system.

This then alters the ant's behaviour such that a drop in temperature that would normally force the insect underground, sees it instead climb to the top of a blade of grass and clamp down on it.
It is then eaten by grazing sheep and the flatworm's life cycle continues in the animal's gut.

'It was the first I learned about this kind of manipulation, so it made a big impression on me,' Flegr says.
A PARASITE'S LIFE
After an infected cat defecates, Flegr learned, the parasite is typically picked up from the soil by scavenging or grazing animals - such as rodents, pigs and cattle- all of which then harbor it in their brain and other body tissues.
Humans are exposed not only by coming into contact with litter boxes, but also, Flegr found, by drinking water contaminated with cat feces, eating unwashed vegetables, or, especially in Europe, by consuming raw or undercooked meat.
The French, according to Flegr, with their love of raw steak can have infection rates as high as 55 per cent, compatred with 10 to 20 per cent of the UK population and 22 per cent of the US population who are estimated to carry the parasite as cysts.
Flegr says he then began to notice similarities between his behaviour and that of the reckless ant.
For example, he says, he thought nothing of crossing a busy road, 'and if cars honked at me, I didn’t jump out of the way', he told The Atlantic.

He says he also refused to hide his contempt for the Communists who ruled Czechoslovakia for most of his early adulthood.

'It was very risky to openly speak your mind at that time,' he says. 'I was lucky I wasn’t imprisoned.'

And during time he spent in eastern Turkey, he says he was able to stay 'very calm' during gunfire, while 'my colleagues were terrified. I wondered what was wrong with myself'.
He believes that large numbers of humans could be similarly afflicted with toxoplasmosis, and that it explains reckless behaviour in many humans.
He says those infected with the parasite are, for example, at greater risk of traffic accidents.
His claims come after a study at Leeds University showed the parasite affects the production of dopamine - the chemical that carries messages in the brain controlling aspects of movement, cognition and behaviour - thus triggering schizophrenia and other bipolar disorders.

The parasite infects the brain by forming a cyst within its cells and produces an enzyme called tyrosine hydroxylase, which is needed to make dopamine.

Dopamine’s role in mood, sociability, attention, motivation and sleep patterns are well documented. Dopamine is the target of all schizophrenia drugs on the market.

Individuals with schizophrenia are also more likely to report a clinical history of toxoplasmosis than those in the general population, other studies have shown.
Dr Glenn McConkey, lead researcher on the Leeds University project: 'It’s highly unlikely that we will find one definitive trigger for schizophrenia as there are many factors involved, but our studies will provide a clue to how toxoplasmosis infection - which is more common than you might think – can impact on the development of the condition in some individuals.
The toxoplasma parasite affects rats in a similar way to humans
'In addition, the ability of the parasite to make dopamine implies a potential link with other neurological conditions such as Parkinson’s Disease, Tourette’s syndrome and attention deficit disorders,' said Dr McConkey.
'We’d like to extend our research to look at this possibility more closely.'

It is unclear why the parasite has chosen humans as a host. The effect on rodents, however, is more obvious.
In studies, infected rodents were much more active in running wheels than uninfected ones, suggesting they would be more attractive targets for cats, which are drawn to fast-moving objects.
They also were less wary of predators in exposed spaces, Flegr says.
Thus rodents are more easily caught by cats and the parasite can continue its life cycle.
Similar findings suggested the parasite makes rats less scared of - and indeed almost attracted to - cats.
Joanne Webster, a parasitologist at Imperial College London, also suggest rats would be likely targets for behavioral manipulation from a a parasite that can only thrive in cats

She found, as previous researchers had shown, that infected rats were more active and less cautious in areas where predators lurk.
But then, in another experiment she treated one corner of each rat’s enclosure with the animal’s own odor, a second with water, a third with cat urine, and the last corner with the urine of a rabbit, a creature that does not prey on rodents.

'We thought the parasite might reduce the rats’ aversion to cat odour,' she told me. 'Not only did it do that, but it actually increased their attraction. They spent more time in the cat-treated areas.'

Separate studies have linked the parasite to increased rates of suicide, according to Teodor Postolache, a psychiatrist and the director of the Mood and Anxiety Program at the University of Maryland School of Medicine.
He looked at a raft of studies that included investigations of general populations as well as groups made up of patients with bipolar disorder, severe depression, and schizophrenia, and in places as diverse as Turkey, Germany, and the Baltimore/Washington area in the U.S.
Though exactly how the parasite may push vulnerable people over the edge is yet to be determined.

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[khmerhit]

and from nat geo==

Toxoplasma – the brain parasite that influences human culturePosted by Ed Yong on October 5, 2008
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We like to think that we are masters of our own fates. The thought that others might be instead controlling our actions makes us uneasy. We rail against nanny states, we react badly to media hype and we are appalled at the idea of brainwashing. But words and images are not the only things that can affect our brains and thoughts. Other animals – parasites – can do this too. According to research by Kevin Lafferty from the University of California, Santa Barbara, a common brain parasite, Toxoplasma gondii, could be influencing human culture across the globe.

Toxoplasma gondii is a single-celled brain parasite spread by cats. Our feline companions are its preferred home and only in their bodies can it mature and reproduce. So like most parasites, T.gondii has a complex life cycle designed to get it into its final host. If it finds itself in another animal, it travels to the brain and changes the host’s behaviour to maximise its chances of ending up in a cat. For rodents, this means being eaten and infected individuals are less fearful of cats and more active, making them easier prey.

Humans can also contract the parasite, through contact with soil contaminated by the faeces of carriers or through eating infected meat. But since cats are very unlikely to eat humans, T.gondii reaches a cul-de-sac in our bodies. Still, there is nothing to stop the parasite, evolutionarily speaking, from trying out the strategies that work so well in other hosts. In rare cases, T.gondii infection causes a disease called toxoplasmosis that produces mild flu-like symptoms and only really threatens foetuses and those with weak immune systems. But in most instances, the parasite acts more subtly.


Carriers tend to show long-term personality changes that are small but statistically significant. Women tend to be more intelligent, affectionate, social and more likely to stick to rules. Men on the other hand tend to be less intelligent, but are more loyal, frugal and mild-tempered. The one trait that carriers of both genders share is a higher level of neuroticism – they are more prone to guilt, self-doubt and insecurity.

In individuals cases, these effects may seem quirky or even charming but across populations, they can have a global power. T.gondii infection is extremely common and rates vary greatly from country to country. While only 7% of Brits carry the parasite, a much larger 67% of Brazilians are infected. Given that the parasite alters behaviour, infection on this scale could lead to sizeable differences in the general personalities of people of different nationalities. This is exactly what Lafferty found.

Neuroticism is one of the most widely-studied of all psychological traits and Lafferty found that levels in different countries correlated well with the levels of T.gondii infection. The parasites’ presence was also related to aspects of culture associated with neuroticism. Countries where infection was common were more likely to have ‘masculine sex roles’, characterized by greater differences between the sexes and their part in society and a stronger focus on work, ambition and money rather than people and relationships. Strongly infected societies were also more likely to avoid risk and embrace strict rules and regulations.

Obviously, different countries are also not just uniform populations, and increasing rates of migration mean that many countries are very ethnically and culturally mixed. However, this works in favour of Lafferty’s theory as any mixing would serve to mask the link between infection and culture. If anything, the link is stronger than seen in this study.

These results are obviously very controversial and it would be imprudent to suggest that T.gondii is the major driver of human culture. It is just one of a number of influences that include genes, our physical environment and our histories. And Lafferty himself is quick to point out caveats to his own results.

For a start, they do not imply that the parasite is causing these personality types; it could be that people with these traits are more likely to become infected. To establish the true direction of causality, Lafferty will need to find out how the parasite manipulates the mind. The general idea is that infection alters levels of the immune system’s communication chemicals – the cytokines – which in turn alter levels of neurotransmitters like dopamine. But the details remain a mystery.

Nonetheless, the results are striking and one implicaiton is that climate could have a larger effect on culture than previously thought. Toxoplasma gondii‘s eggs live longer in humid, low regions so variations in climate could influence the global distribution of cultural traits. Perhaps, this could explain why men and women perform more distinct roles in society in countries in warmer climates. Other factors can also affect the risk of infection, including cat ownership and national cuisines that include undercooked meat.

We like to think of culture as something governed by the collective actions of free-thinking and free-acting humans. But Lafferty’s analysis shows us that if environmental factors like parasites can affect our thoughts and actions, no matter how subtly, they can have a strong effect on national cultures. In many cases, these effects could be much stronger than the agents that we normally believe to drive cultural trends. After all, more people around the world are infected with Toxoplasma than are connected to the internet.

Reference: Kevin D. Lafferty (2006). Can the common brain parasite, Toxoplasma gondii, influence human culture? Proceedings of the Royal Society B: Biological Sciences, 273 (1602), 2749-2755 DOI: 10.1098/rspb.2006.3641


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Comments
ringo

October 5, 2008, 11:08 am I would also expect to see gender and SES differences in infection rates, if contact with infected soil were the primary transmission channel (who changes the cat box? who works in the garden?).

I wonder if neurotransmitters are really the trigger for behavior changes, however. A simple change in balance (like you would get from one alcoholic drink) would be enough to make people more neurotic and less willing to take risks (thus more likely to just follow the rules, and seek out groups). In mice, that would translate to a preference for running on the ground versus climbing – obviously an advantage for the parasite.

nanook

October 5, 2008, 2:42 pm “For a start, they do not imply that the parasite is causing these personality types; it could be that people with these traits are more likely to become infected”

you know, the artice should have started with a sentence like this. because not everyone does photoreading. most readers get stuck with the impression of the first paragraphs.

the scientific and journalistic competition of spreading the most rediculous rumor does not match everyones sense of humor. and it is a cultural virus.

Ambigram

October 5, 2008, 3:15 pm It would however be a serious lie of omission not to point out the following passages:

Two dramatic outliers were South Korea and Japan, which had lower prevalence than expected. When only Western nations were analysed (i.e. excluding China, South Korea, Japan, Turkey and Indonesia), uncertainty avoidance (n=27, R2=0.15, p=0.017) and masculine sex roles (n=27, R2=0.27, p=0.003) increased significantly with the prevalence of T. gondii (figures 2 and 3). There were two significant outliers for uncertainty avoidance among Western nations: Jamaica had less uncertainty avoidance than expected and Greece had more uncertainty avoidance than expected.

(i.e. West-Asia differences, of no small interest in many quarters, cannot be accounted for this way)

These results are thought-provoking, but several caveats are important to consider when interpreting the data. Since this study is correlative, it is impossible to confirm causation (e.g. the analysis cannot reject the alternative interpretation that aggregate personality or cultural dimension alters risk of exposure), or to exclude the possibility of spurious results (i.e. non-causal correlations between aggregate personality and aspects of climate and culture that influence T. gondii transmission).

(i.e. causation was not established)

What leads to variation in exposure? Differences in exposure risk cause wide variation in T. gondii prevalence among human populations. In particular, climate can alter exposure risk. Oocysts live longer in humid, low altitude regions, especially at mid-latitudes with infrequent freezing and thawing (Walton et al. 1966; Dubey 1974; Dubey & Beattie 1988). The resulting geographical variation in the risk of T. gondii in humans could indirectly lead to geographical variation in cultural dimensions, potentially explaining the observation of a greater differentiation of sex roles in warm countries (Hofstede 2001).

(i.e. the results could simply be tracking the influence of a warm climate on human behaviour)

Honestly this reminds me of the putrid science journalism that swirled around the “men like blue, women like pink” study, which oddly enough didn’t even involve the colour pink.

Science journalism should seek to inform the public; this smacks of a Nisbettian desire to simply reinforce popular prejudice.

Ambigram

October 5, 2008, 3:32 pm It seems Nanook beat be to the punch on point 2. In any case, all our points still stand.

Max

October 6, 2008, 3:29 pm I actually tend to agree with the previous two posts — in the article, the scientist is quoted as mentioning that there’s not necessarily causation, only correlation, while the title of this blog post suggests causation. Regardless, if it is just a coincidence, it’s a very interesting coincidence.

Nathan Myers

October 7, 2008, 7:01 am What I want to know is (1) is there a safe, reliable test to detect whether I’m infected, and (2) is there a safe, reliable treatment to eliminate it?

Daniel

October 7, 2008, 11:10 am Isn’t the strongest correlation here in the wealth of a country? After all, the chance of contracting a disease by “contact with soil contaminated by the faeces of carriers or through eating infected meat” is going to decrease with wealth. And oh, that explains why Japan doesn’t have as much infection as expected by this theory.

So then the title becomes “money influences culture” which isn’t half as interesting! Though its possible that this is one mechanism for how it might do so.

cabbagepow

October 10, 2008, 11:10 am In mice, that would translate to a preference for running on the ground versus climbing – obviously an advantage for the parasite

[khmerhit]

from wikipedia--

[edit] ToxoplasmosisMain article: Toxoplasmosis

Diagram of Toxoplasma gondii structureT. gondii infections have the ability to change the behavior of rats and mice, making them drawn to, rather than fearful of, the scent of cats. This effect is advantageous to the parasite, which will be able to sexually reproduce if its host is eaten by a cat.[17] The infection is widespread in the brain, with more cysts targeting the parts of the brain corresponding to fear. The widespread nature of the infection causes many previously unnoticed symptoms in the rats.[18]

Studies have also shown behavioral changes in humans, including lower reaction times and a sixfold increased risk of traffic accidents among infected, RhD-negative males,[19] as well as links to schizophrenia including hallucinations and reckless behavior. Recent epidemiologic studies by Stanley Medical Research Institute and Johns Hopkins University Medical Center indicate that infectious agents may contribute to some cases of schizophrenia.[20][21] A study of 191 young women in 1999 reported higher intelligence and higher guilt proneness in Toxoplasma-positive subjects.[22]

The prevalence of human infection by Toxoplasma varies greatly between countries. Factors that influence infection rates include diet (prevalence is possibly higher where there is a preference for less-cooked meat) and proximity to cats.[23]

According to Merck the standard treatment for toxoplasmosis is pyrimethamine, but most immunocompetent asymptomatic people infected with T. gondii, with the exception of neonates and pregnant women, require no treatment.[24]

[edit] HistoryThe organism was first described in 1908 in Tunis by Charles Nicolle and Louis Manceaux within the tissues of the gundi (Ctenodactylus gundi). In the same year it was also described in Brazil by Alfonso Splendore in rabbits.

[edit] References^ Ryan KJ, Ray CG (eds) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. pp. 722–7. ISBN 0-8385-8529-9.
^ Dubey JP, Webb DM, Sundar N, Velmurugan GV, Bandini LA, Kwok OC, Su C. (2007-09-30). "Endemic avian toxoplasmosis on a farm in Illinois: clinical disease, diagnosis, biologic and genetic characteristics of Toxoplasma gondii isolates from chickens (Gallus domesticus), and a goose (Anser anser)". Vet Parasitol. 148 (3–4): 207–12. DOI:10.1016/j.vetpar.2007.06.033. PMID 17656021.
^ a b Boothroyd JC (July 2009). "Toxoplasma gondii: 25 years and 25 major advances for the field". International Journal for Parasitology 39 (8): 935–46. DOI:10.1016/j.ijpara.2009.02.003. PMC 2895946. PMID 19630140. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2895946.
^ Dubey, JP; Lindsay, DS; Speer, CA (1998). "Structures of Toxoplasma gondii tachyzoites, bradyzoites, and sporozoites and biology and development of tissue cysts". Clinical Microbiology Reviews 11 (2): 267–99. PMC 106833. PMID 9564564. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=106833.
^ Blader, IRA J.; Saeij, Jeroen P. (2009). "Communication betweenToxoplasma gondiiand its host: Impact on parasite growth, development, immune evasion, and virulence". APMIS 117 (5–6): 458–76. DOI:10.1111/j.1600-0463.2009.02453.x. PMC 2810527. PMID 19400868. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2810527.
^ Lavine, MD; Arrizabalaga, G (2008). "Exit from host cells by the pathogenic parasite Toxoplasma gondii does not require motility". Eukaryotic cell 7 (1): 131–40. DOI:10.1128/EC.00301-07. PMC 2224157. PMID 17993573. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2224157.
^ Dvorak, J.; Crane, M. (1981). "Vertebrate cell cycle modulates infection by protozoan parasites". Science 214 (4524): 1034–6. DOI:10.1126/science.7029713. PMID 7029713.
^ Grimwood, J; Mineo, JR; Kasper, LH (1996). "Attachment of Toxoplasma gondii to host cells is host cell cycle dependent". Infection and immunity 64 (10): 4099–104. PMC 174343. PMID 8926075. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=174343.
^ Youn, J H; Nam, H W; Kim, D J; Park, Y M; Kim, W K; Kim, W S; Choi, W Y (1991). "Cell cycle-dependent entry of Toxoplasma gondii into synchronized HL-60 cells". The Korean Journal of Parasitology 29 (2): 121–8. DOI:10.3347/kjp.1991.29.2.121.
^ Coppens, Isabelle; Dunn, Joe Dan; Romano, Julia D.; Pypaert, Marc; Zhang, Hui; Boothroyd, John C.; Joiner, Keith A. (2006). "Toxoplasma gondii Sequesters Lysosomes from Mammalian Hosts in the Vacuolar Space". Cell 125 (2): 261–74. DOI:10.1016/j.cell.2006.01.056. PMID 16630815.
^ Walker, Margaret E.; Hjort, Elizabeth E.; Smith, Sherri S.; Tripathi, Abhishek; Hornick, Jessica E.; Hinchcliffe, Edward H.; Archer, William; Hager, Kristin M. (2008). "Toxoplasma gondii actively remodels the microtubule network in host cells". Microbes and Infection 10 (14–15): 1440–9. DOI:10.1016/j.micinf.2008.08.014. PMC 2765197. PMID 18983931. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2765197.
^ "Invitro effects of ivermectin and sulphadiazine on Toxoplasma gondii" 20th European Congress of Clinical Microbiology and Infectious Diseases.
^ "Invitro effects of ivermectin and sulphadiazine on Toxoplasma gondii". 20th European Congress of Clinical Microbiology and Infectious Diseases. April 2010.
^ Rorman, Efrat; Zamir, Chen Stein; Rilkis, Irena; Ben-David, Hilla (May 2006). "Congenital toxoplasmosis—prenatal aspects of Toxoplasma gondii infection". Reproductive Toxicology 21 (4): 458-472. DOI:10.1016/j.reprotox.2005.10.006.
^ Groër, Maureen W.; Yolken,, Robert H.; Xiao, J.-C.; Beckstead, Jason W.; Fuchs, Dietmar; Mohapatra, Shyam S.; Seyfang, Andreas; Postolache, Teodor T. (May 2011), "Prenatal depression and anxiety in Toxoplasma gondii–positive women", American Journal of Obstetrics and Gynecology 204 (5): 433.e1-433.e7, DOI:10.1016/j.ajog.2011.01.004
^ Okusaga, Olaoluwa; Langenberg, Patricia; Sleemi, Aamar; Vaswani, Dipika; Giegling, Ina; Hartmann, Annette M.; Konte, Bettina; Friedl, Marion et al. (December 2011), "Toxoplasma gondii antibody titers and history of suicide attempts in patients with schizophrenia", Schizophrenia Research 133 (1-3): 150-155, DOI:10.1016/j.schres.2011.08.006
^ Berdoy M, Webster JP, Macdonald DW (August 2000). "Fatal attraction in rats infected with Toxoplasma gondii". Proc. Biol. Sci. 267 (1452): 1591–4. DOI:10.1098/rspb.2000.1182. PMC 1690701. PMID 11007336. http://journals.royalsociety.org/openur ... spage=1591.
^ theatlantic.com
^ Flegr J, Klose J, Novotná M, Berenreitterová M, Havlíček J (2009). "Increased incidence of traffic accidents in Toxoplasma-infected military drivers and protective effect RhD molecule revealed by a large-scale prospective cohort study". BMC Infectious Diseases 9: 72. DOI:10.1186/1471-2334-9-72. PMC 2692860. PMID 19470165. http://www.biomedcentral.com/1471-2334/9/72.
^ cdc.gov
^ newscientist.com
^ Flegr J.; Havlícek J. (1999). Changes in the personality profile of young women with latent toxoplasmosis. Folia Parasitologica (Praha). 46(1):22-8. Note that the abstract misquotes the body text by reporting lower guilt proneness; findings, mentioned in several places in the text, were for high guilt proneness, not lower.
^ Meerburg BG, Kijlstra A (2009). "Changing climate—changing pathogens: Toxoplasma gondii in North-Western Europe". Parasitology Research 105 (1): 17–24. DOI:10.1007/s00436-009-1447-4. PMC 2695550. PMID 19418068. http://www.springerlink.com/content/6k40766145g56746.
^ Pearson, Richard D. (December 2009). "Toxoplasmosis". The Merck Manual. Merck Sharp & Dohme Corp.. http://www.merckmanuals.com/professiona ... mosis.html. Retrieved 13 February 2012.
[edit] External linksToxoDB : The Toxoplasma gondii genome resource
Anti-Toxo : A Toxoplasma news blog and list of research laboratories
Toxoplasma images, from CDC's DPDx, in the public domain
Toxoplasmosis Research Institute & Center
Cytoskeletal Components of an Invasion Machine — The Apical Complex of Toxoplasma gondii
The Culture-Shaping Parasites, in Seed Magazine
Sneaky Parasite Attracts Rats to Cats, All Things Considered, April 14, 2007
Toxoplasma overview, developmental stages, life cycle image at MetaPathogen
Toxoplasma lecture, Robert Sapolsky
[dead link] Could a brain parasite found in cats help soccer teams win at the World Cup? - By Patrick House - Slate Magazine
How Your Cat Is Making You Crazy, the Atlantic Magazine, March 2012
Mystery Marine Mammal Deaths, CosmosMagazine.com, June 2008
[show]v · t · e SAR: Chromalveolata: Alveolata

Ciliophora Postciliodesmatophora Heterotrichea (Stentor) · Karyorelictea (Loxodes)

Intramacronucleata Spirotrichea (Stylonychia) · Litostomatea (Didinium, Balantidium) · Phyllopharyngea (Tokophrya) · Nassophorea (Nassula) · Colpodea (Colpoda) · Oligohymenophorea (Tetrahymena, Ichthyophthirius, Vorticella, Paramecium) · Plagiopylea (Plagiopyla) · Prostomatea (Coleps)

Other Cryptocaryon


Myzozoa Apicomplexa Aconoidasida Haemospororida Garniidae (Garnia) · Haemoproteidae (Haemoproteus) · Leucocytozoidae (Leucocytozoon) · Plasmodiidae (Plasmodium)

Piroplasmida Babesiidae (Babesia) · Theileridae (Theileria)


Conoidasida Coccidia Agamococcidiorida Gemmocystidae (Gemmocystis), Rhytidocystidae (Rhytidocystis)

Eucoccidiorida Adeleorina Haemogregarina, Hepatozoon, Karyolysus

Eimeriorina Cryptosporidiidae (Cryptosporidium)
Eimeriidae (Cyclospora, Eimeria, Isospora)
Sarcocystidae (Besnoitia, Neospora, Sarcocystis, Toxoplasma)


Ixorheorida Ixorheidae (Ixorheis)

Protococcidiorida Angeiocystidae · Eleutheroschizonidae (Defretinella) · Grelliidae · Mackinnoniidae · Myriosporidae


Gregarinia Archigregarinorida Exoschizonidae · Selenidioididae

Eugregarinorida Aseptatorina · Blastogregarinorina · Cephaloidophoridae · Cephalolobidae · Ganymedidae · Porosporidae · Uradiophoridae · Septatorina

Neogregarinorida Caulleryellidae · Gigaductidae · Lipotrophidae · Ophryocystidae · Schizocystidae · Syncystidae




Chromerida Chromeraceae (Chromera velia), Vitrellaceae (Vitrella brassicaformis)

Colpodellida Colpodellidae (Acrocoelus, Colpodella)

Dinoflagellata Dinokaryota With a theca: Peridiniales (Pfiesteria, Peridinium) · Gonyaulacales (Ceratium, Gonyaulax) · Prorocentrales (Prorocentrum) · Dinophysiales (Dinophysis, Histioneis, Ornithocercus, Oxyphysis)
Without theca: Gymnodiniales (Gymnodinium, Karenia, Karlodinium, Amphidinium) · Suessiales (Polarella, Symbiodinium)

Noctilucea Noctilucales (Noctiluca)

Syndinea Syndiniales: Amoebophryaceae (Amoebophyra) · Duboscquellaceae (Duboscquella) · Syndiniaceae (Hematodinium, Syndinium)

Other Oxyrrhinaceae (Oxyrrhis)


Dinozoa Colponemea Algovoridae (Algovora) · Colponemidae (Colponema)

Ellobiopsea Ellobiopsidae (Elliobiocystis, Ellobiopsis, Thalassomyces)

Myzomonadea Chilovorida Chilovoridae (Chilovora)

Voromonadida Alphamonadidae (Alphamonas) · Voromonadidae (Voromonas)



Perkinsozoa Perkinsea Cryptophagus · Perkinsidae (Perkinsus) · Phagodinida (Phagodinium) · Rastromonadida (Parvilucifera, Rastromonas)


Unclassified Perkinsoide chabelardi


M: PRO
ambz, excv, chrm (strc)
ambz, excv, chrm
ambz, excv, chrm




[show]v · t · e Infectious diseases – Parasitic disease: protozoan infection: Chromalveolate and Archaeplastida (A07,

[khmerhit]

from the economist--

Toxoplasmosis and psychology
A game of cat and mouse
There is tantalising evidence that a common parasite may affect human behaviour
Jun 3rd 2010 | from the print edition

IF AN alien bug invaded the brains of half the population, hijacked their neurochemistry, altered the way they acted and drove some of them crazy, then you might expect a few excitable headlines to appear in the press. Yet something disturbingly like this may actually be happening without the world noticing.

Toxoplasma gondii is not an alien; it is a relative of that down-to-earth pathogen Plasmodium, the beast that causes malaria. It is common: in some parts of the world as much as 60% of the population is infected with it. And it can harm fetuses and people with AIDS, because in each case their immune systems cannot cope with it. For other people, though, the symptoms are usually no worse than a mild dose of flu. Not much for them to worry about, then. Except that there is a growing body of evidence that some of those people have their behaviour permanently changed.

One reason to suspect this is that a country's level of Toxoplasma infection seems to be related to the level of neuroticism displayed by its population. Another is that those infected seem to have poor reaction times and are more likely to be involved in road accidents. A third is that they have short attention spans and little interest in seeking out novelty. A fourth, possibly the most worrying, is that those who suffer from schizophrenia are more likely than those who do not to have been exposed to Toxoplasma.

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Nor is any of this truly surprising. For, besides humans, Toxoplasma has two normal hosts: rodents and cats. And what it does to rodents is very odd indeed.

Fatal feline attraction

Joanne Webster of Imperial College, London, has been studying Toxoplasma for years. Like Plasmodium, which cycles between mosquitoes and man, Toxoplasma cycles between its rodent and feline hosts, living out different phases of its existence in each. In cats, it resides in the wall of the small intestine and passes out of the host in its faeces. These are then picked up by rats and mice (and also by other mammal species, including humans), where they form cysts in brain, liver and muscle tissue. Eventually, if the parasites are lucky, their rodent host is eaten by a cat and the whole cycle starts again.

Unlike Plasmodium, however, which can rely on the natural behaviour of mosquitoes to spread it around, Toxoplasma's rodent hosts have a strong aversion to helping it into its next home. Which is where, in Dr Webster's elegant phrase, fatal feline attraction comes in. Rats and mice infected with Toxoplasma start wandering around and drawing attention to themselves—in other words, behaving in ways that will bring them to the attention of cats. They are even, Dr Webster's work suggests, attracted to the smell of cats.

How these behavioural changes come about was, until recently, obscure. But in 2009 Glenn McConkey of the University of Leeds, in England, analysed Toxoplasma's DNA. When he compared the results with those of other species, he discovered that two of the bug's genes encode enzymes involved in the production of a molecule called dopamine. This molecule acts, in animals that have nervous systems, as a chemical messenger between nerve cells. It does not, however, have any known function in single-celled critters. Moreover, dopamine is particularly implicated in schizophrenia. Haloperidol, an antipsychotic drug, works by blocking dopamine receptors.

Intriguingly, Dr Webster has found that haloperidol serves to reverse fatal feline attraction in rats. This suggests the parasite is indeed interfering with the brain's dopamine system—and thus that it might be doing the same thing in people. Dr McConkey is now making a version of Toxoplasma with the dopamine genes excised, to see if rats infected with this modified bug are protected from the fatal attraction.

Culture club

The evidence that human toxoplasmosis does more than appears at first sight is, it must be said, quite scattered. But it is intriguing and probably worth following up.

The connection with schizophrenia was originally suggested in the 1950s, but only really took off in 2003, when it was revived by Fuller Torrey of the Stanley Medical Research Institute, near Washington, DC. In collaboration with Bob Yolken of Johns Hopkins University, Dr Fuller discovered that people who suffer from schizophrenia are almost three times more likely than the general population to have antibodies to Toxoplasma.

That does not, of course, prove Toxoplasma causes schizophrenia. As every science student is taught from the beginning, correlation is not causation. It could be that schizophrenics are more susceptible to the infection, or some third, as yet unidentified variable may be involved.

Another interesting correlation has, though, been discovered by Jaroslav Flegr of Charles University in Prague. Dr Flegr has studied several aspects of the Toxoplasma question. In one case he looked at the infection rate of people involved in road accidents. Both drivers and pedestrians who had been in accidents were almost three times more likely to be infected than comparable individuals who had not been. Similar results have been found in Turkey, by Kor Yereli of Celal Bayar University, in Manisa. And Dr Flegr has found other abnormalities in infected people. These included reduced reaction times and shorter attention spans—both of which might help to explain the accident statistics—and a reduction in “novelty-seeking”.

This latter is curious. The sort of behaviour shown by rodents is, if anything, an increase in novelty-seeking. But the point is that novelty-seeking is controlled by nerve cells that respond to dopamine. Humans are dead-end hosts as far as Toxoplasma is concerned, so the exact effect will not have been honed by natural selection and may therefore be different from the one in animals that are actually useful to the parasite.

All of these suggested effects are obviously bad for the individuals involved, but some researchers go further and propose that entire societies are being altered by Toxoplasma. In 2006 Kevin Lafferty of the University of California, Santa Barbara, published a paper noting a correlation between levels of neuroticism established by national surveys in various countries and the level of Toxoplasma infection recorded in pregnant women (a group who are tested routinely). The places he looked at ranged from phlegmatic Britain, with a neuroticism score of -0.8 and a Toxoplasma infection rate of 6.6%, to hot-blooded France, which scored 1.8 and had an infection rate of 45%. Cross-Channel prejudices, then, may have an unexpected origin.

To repeat, correlation is not causation, and a lot more work would need to be done to prove the point. But it is just possible that a parasite's desire to get eaten by a cat is shaping the cultures of the world.

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