[lawcat]

Well, your cat(s) might just drive you retarded with their feces.

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The parasite, which is excreted by cats in their feces, is called Toxoplasma gondii (T. gondii or Toxo for short) and is the microbe that causes toxoplasmosis—the reason pregnant women are told to avoid cats’ litter boxes. Since the 1920s, doctors have recognized that a woman who becomes infected during pregnancy can transmit the disease to the fetus, in some cases resulting in severe brain damage or death. T. gondii is also a major threat to people with weakened immunity: in the early days of the AIDS epidemic, before good antiretroviral drugs were developed, it was to blame for the dementia that afflicted many patients at the disease’s end stage. Healthy children and adults, however, usually experience nothing worse than brief flu-like symptoms before quickly fighting off the protozoan, which thereafter lies dormant inside brain cells—or at least that’s the standard medical wisdom

http://www.theatlant...you-crazy/8873/

[Turtle]

yikes!!

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...
But if Flegr is right, the “latent” parasite may be quietly tweaking the connections between our neurons, changing our response to frightening situations, our trust in others, how outgoing we are, and even our preference for certain scents. And that’s not all. He also believes that the organism contributes to car crashes, suicides, and mental disorders such as schizophrenia. When you add up all the different ways it can harm us, says Flegr, “Toxoplasma might even kill as many people as malaria, or at least a million people a year.” ...

i do not currently own a cat or cats, i will not in the future own a cat or cats, but in the past i have owned several individual cats on & off over a period of 10 or 15 years.

fascinating. the biology of desire?

[CraigD]

lawcat, on 11 February 2012 - 04:55 PM, said:

http://www.theatlant...you-crazy/8873/

I think Kathleen McAuliffe’s Atlantic article is superbly written and subject-chosen, no surprise, as she’s well-educated (1970s M.A. in natural science with a thesis in EEG recordings) and experienced (about 30 years) biomedical journalist with a string of awards and influential articles to her credit, and long married to a pro physicist, which can’t hurt. Like most of the better science articles, it’s fairly long (about 5,900 words, nearly 9 times the length of this post), but IMO well-worth a full, careful, thoughtful read.

Thought the main theme of the article concentrates on T. gondii, the protozoa known to, I’d estimate, at least half the world, due to the risk it poses if contracted by a human during pregnancy, it notes that it’s very likely that T. gondii is just one of many similar parasites that can profound effects the cognition and behavior not only of such animals as ants and rats, but of humans. The science support this last claim seems solid and dramatic. In multiple studies, large T. gondii positive human population show clear differences in various statistics – for example, a study primarily of male drivers in the Czech military found T. gondii positive drivers to be 2.5 times more likely to have a traffic accident than T. gondii negative ones.

It’s been well-known and, while amazing, hardly controversial, that parasites can alter the behavior of hosts such as ants and rats in ways that benefit the parasites. The life cycle of Dicrocoelium dendriticum flatworm parasite, which causes infected ants to weirdly climb to the tops of grass where they’re eaten by sheep, has been understood for 60 years. That T. gondii in rats causes them to be more active and careless, which is good for T. gondii, as such rats are easier meals for cats, which T. gondii must be in to reproduce sexually, has been known for more than 10 years. That infected male rats were actually attracted to the cat urine – and thus to cat territory – was shown in 2011.

But that T. gondii causes infected human males to find cat urine scent less offensive than uninfected men find it – and thus, with a bit of an imaginative stretch, “controlling our minds” to make humans more kindly disposed to cats, thus indirectly benefitting T. gondii, is fairly shocking.

I find it all delightfully fascinating. It really drives home some key concepts of evolutionary biology, one regarding the non-necessity of conscious planning in evolution. T. gondii are protozoa (the same collection of nucleus-possessing single celled organisms as amoeba), lacking anything approaching the machinery needed for thinking. They clearly didn’t plan to tweak cats and humans’ minds to improve their reproductive success. Rather, of many protozoa parasites, T. gondii (and possibly many similar species) “succeeded without trying” reproductively because of a quirk of their physio-chemistry. This quirk appears to consists of a couple of genes that express proteins that cause increased dopamine production in mammal brains. Dopamine plays many neurochemical roles, including producing feelings of pleasure and calm fearlessness.

Unfortunately, and getting back to McAuliffe’s article’s title, How Your Cat Is Making You Crazy, dopamine overproduction appears to be responsible for many schizophrenias. One of the findings described in the article is that a neuroanatomically feature found in some schizophrenics – shrinking of certain brain structures – almost perfectly correlates with their being T. gondii positive. Like McAuliffe when she first read it, this stunned me. Many schizophrenics may be crazy because of becoming infected with T. gondii from feces (or, less commonly, bites or scratches) from housecats – quite literally, their cats made them crazy!

Before deciding on a cat-exterminating health campaign (and you’d get a fight from me before I’d let you harm a hair on the fur of my 2 cats!), note that T. gondii is found in many animals, including pigs and cows. Likely the most common human infection vector is eating rare-cooked meat, not cat feces.

Some key statistics from the article: the T. gondii infection rate among Americans is from 10-20%; among the French, as high as 55%. The difference is hypothesized to be due to the French eating more rare meat.

[lawcat]

It certainly gives a scientific meaning to the expression, crazy cat lady.

I am interested to know how the parasites can be eliminated or controlled, and whether labs check for this when urin or blod is sent in, and whether interpreting physicians pay attention to this at all when results come back. I love cats and have lived with cats, but not now. I used to let them scratch me when playing. It's a concern certainly.

[CraigD]

lawcat, on 11 February 2012 - 10:06 PM, said:

I am interested to know how the parasites can be eliminated or controlled ...

Eliminated, I’m fairly certain not. T. gondii is a very successful, hearty (able to survive in a moist place outside of a host for perhaps a year) organism with many know, and likely many unknown, hosts, for which there’s no known treatment that will kill it without also killing the host.

From what I’ve read, as with many other pathogens, the best single way to control its transmission to humans is to thoroughly cook (or be a vegetarian, an completely avoid) meat, and consistently wash fresh vegetables. Especially, don’t eat raw mice or rats! and keep cats from doing so (keep them inside), though if you depend on barn cats to control mice and rats, this may not be practical.

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... and whether labs check for this when urin or blod is sent in, and whether interpreting physicians pay attention to this at all when results come back.

There’s currently no effective blood screening test for Toxoplasmosis (the condition of having an acute immune response to a T. gondii infection), so no. To the best of my knowledge, like most microorganisms and antibodies, T. gondii and antibodies to it are not present in urine.

Until fairly recently (the mid 1990s) T. gondii could be nearly impossible to detect, because the antibodies produces in response to an initial infection of it are present in detectable amounts only for a few weeks. Fortunately, the major severe toxo health risk, miscarriage, stillbirth, neonatal death, and birth defects due to an initial infection in pregnant women, need be tested for only around the third month of a pregnancy, so the antibody test are fairly effective in detecting it, and common safe, effective, inexpensive drug treatments are possible.

I’ve not found much literature about it, but am able to infer that an immune-normal (that is, not having an immune-compromising disease, such as HIV/AIDS) woman previously infected with T. gondii is immune from contracting another infection of it, so is at not at risk if she has a baby.

It’s been shown in rats (per the article) that T. gondii can be passed sexually. I’m very curious to know if this occurs in humans and other animals.

Since the 1990s, there’s been a reasonably cheap (about US$400) PCR gene-finding T. gondii test. I assume this is the one that McAuliffe took while writing the article, and Jaroslav Flegr and other use in their research correlating memory and reasoning testing, car driving, brain abnormalities, etc. with T. gondii. Infection.

(sources: http://www.bloodbook...trans-tran.html, http://www.dpd.cdc.g...osis_serol1.htm, http://www.pamf.org/...ogy/pcrfee.html)

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I love cats and have lived with cats, but not now. I used to let them scratch me when playing. It's a concern certainly.

I wouldn’t worry too much, or not keep a pet cat if you’d like, because, as with transmission to a fetus during pregnancy, a cat can only give you toxoplasmosis during a few weeks after it is initially infected with it. So if the cat that scratched you with its feces contaminated claws hasn’t been in contact with rats, mice, or strange cats for the past month (a good reason to keep pet cats indoors constantly), there’s less chance of you getting it from a cat than from carelessly prepared food.

[lawcat]

Craig, that's awesome, thank you!

[Turtle]

CraigD, on 12 February 2012 - 09:29 AM, said:

...
I wouldn’t worry too much, or not keep a pet cat if you’d like, because, as with transmission to a fetus during pregnancy, a cat can only give you toxoplasmosis during a few weeks after it is initially infected with it. So if the cat that scratched you with its feces contaminated claws hasn’t been in contact with rats, mice, or strange cats for the past month (a good reason to keep pet cats indoors constantly), there’s less chance of you getting it from a cat than from carelessly prepared food.

so if i understand correctly that humans inhale the protozoa from dried feces, then besides cat owners, gardners whose gardens free-ranging cats visit for their business may also be at risk of infection, conditioned of course on what you say about the necessary timing for transmission. moreover it is these free ranging cats that are most likely to hunt & eat rats & mice. i keep thinking of the old egyptians & their close association with cats. would there be any recoverable evidence of T. gondii infection from mummies or skeletal remains?

given too that these free-ranging cats hunt & eat birds and T.gondii seems restricted to mammals, i wonder if their is some other yet un-found protazoa that vectors through birds.

[CraigD]

Turtle, on 12 February 2012 - 12:01 PM, said:

so if i understand correctly that humans inhale the protozoa from dried feces, ...

I don’t think this is possible. Like most protozoa, T. gondii can survive being dried – it’s pretty tough, but not that tough.

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... then besides cat owners, gardners whose gardens free-ranging cats visit for their business may also be at risk of infection, conditioned of course on what you say about the necessary timing for transmission. moreover it is these free ranging cats that are most likely to hunt & eat rats & mice.

Yes. Eating cat feces, whether from failing to adequately wash your hands before handling food after cleaning a litter box, or the same when unbeknownst to you, a cat has made your garden his litter box, puts you at risk of toxoplasmosis.

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i keep thinking of the old egyptians & their close association with cats. would there be any recoverable evidence of T. gondii infection from mummies or skeletal remains?

AFAIK, you’d need blood or moist tissue from a fresh cadaver, which you could then PCR to amplify and detect T. gondii DNA, or a fairly intact brain to microscopically examine for the lesions associated with infection with it, so I don’t think detecting it in mummies or bones is possible.

However, I’m pretty sure T. gondii is more ancient than cats or humans, so given that they kept pet cats, had cattle, and weren’t much different in diet from us, it’s a pretty safe bet that ancient Egyptians had an infection rate similar to ours.

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given too that these free-ranging cats hunt & eat birds and T.gondii seems restricted to mammals, i wonder if their is some other yet un-found protazoa that vectors through birds.

T. gondii’s known to be hosted, for the asexual phase of its life cycle, in many warm-blooded animals, including birds, and even sea otters.

I’m not sure any warm-blooded animal isn’t a potential T. gondii host. Unless the host has some way of getting its blood and into a cat, such a host is a reproductive dead end. As I can’t imaging even the most ferocious mouser, and would be surprised if even a bobcat would try taking a sea otter, finding it in them, not just as dead-enders of the usual strain, but as a specialized strain optimized for that host, leads me to suspect they can reproduce sexually not only in housecats, but in the larger cats. I wonder if the really big cats – lions and tigers – are reproductive keys to specialized T. gondii strains, too? Or if any non-felines play this role in similar protozoa parasites? (This 2010 NIH paper indicates that research into “Develop methods for crossing strains in vitro or at least in animals other than cats” – that is, breeding or engineering a T. gondii strain that can reproduce in non-felines - is a target research goal)

How many other parasites, protozoa and more or less, complex, have life cycles similar to T. gondii, I can’t begin to guess, but wouldn’t be surprised if the number is very large. Unless such a parasite causes serious disease, we tend not to care about or be aware of it.

[hardy5]

Great read