Toxoplasmosis: How Parasites in Your Cat Can Infect Your Brain


[♪INTRO] Now this is a common stereotype: the single
lady who lives next door and you hear meows echoing through the walls. Or maybe it’s your aunt, or grandma, with
a whole clowder of cats. Whoever it is, she is known as the “crazy
cat lady.” [tox-oh-plaz-mah gone-dee-eye]
And stereotypes or not, there could be some actual psychological risks from hanging around
so many kitties… if just one of them is harboring a parasite. See, there’s a parasite that only sexually
reproduces only inside cats and it’s called Toxoplasma gondii. And if that parasite gets into a human, it
can result in a full-blown infection called toxoplasmosis, which could be bad news for
your body and your mind. T. gondii have really tough eggs. And when animals like rats or birds eat them,
even just through contaminated water, they become intermediate hosts. Once that bird or rat makes it’s way inside
of a cat — however that happens — in a kitty’s gut, the parasite will mature, mate,
and sexually reproduce. And, eventually, the cat will poop out more
eggs, which continues the cycle. In a human, or other intermediate host, T.
gondii can still hatch but only reproduce asexually. They’re dangerous though, because parasites
can enter your bloodstream and infect almost any kind of cell — including immune cells. An immune cell is like a Trojan horse, letting
T. gondii sneak around and invade more specialized tissues like muscle cells and brain cells. Once parasites get into your central nervous
system, they can hide out in cysts, and infect you for life. But you might not show any symptoms. Or if you do, it’s just like a mild flu. Some estimates even say over a third of all
humans have toxoplasmosis without knowing it. As a human’s immune system gets weaker over
time, the parasitic cysts can cause some more severe symptoms. An infected person can develop muscle weakness,
poor coordination, seizures, or permanent damage to the brain and eyes. Which is not great. And if a pregnant woman is infected, she could
pass the parasites onto her baby. On top of that, there’s evidence that links
T. gondii infection to psychological conditions, too. One study monitored the mental health of nearly
46,000 women from Denmark who had their newborn babies screened for T. gondii antibodies,
which were passed on. The researchers then followed up on the mothers’
medical and psychiatric information for up to 14 years, and found that infected women
seemed to have more risk of depression, anxiety, and self-harm later in life. Many studies suggest that T. gondii affects
how a couple different neurotransmitters work, too. These are the chemicals that travel between
neurons all over the body, not just in the brain. And when neurotransmitters get imbalanced,
that can lead to physical and mental illnesses. One 2011 mouse study from the University of
Leeds showed that T. gondii infection in brain cells led to higher dopamine levels, because
the parasite makes an enzyme that controls how dopamine is made. Dopamine helps regulate parts of the brain tied to pleasure, mostly the amygdala and
nucleus accumbens. But too much dopamine flooding the brain has
been linked with illnesses that distort thoughts and moods, like psychosis, schizophrenia,
and bipolar disorder. A more recent study in 2016 showed that T.
gondii infection can also mess up a protein that transports glutamate, which is usually
an excitatory neurotransmitter that makes neurons more easily activated. Failed transporters lead to a glutamate build-up
in the space between neurons all over the nervous system, like a chemical traffic jam. This is called excitotoxicity, and it basically
overstimulates the nerve cells, causing parts of them to go haywire and start breaking down. So dysregulation of glutamate is linked with
neurodegenerative diseases like ALS, multiple sclerosis, Parkinson’s, and Alzheimer’s. And another study from 2012 found that parasite-hijacked immune cells start releasing a bunch of GABA. GABA is usually an inhibitory neurotransmitter,
which means it can keep neurons from firing as much. When it interacts with the amygdala, for instance,
GABA can help control feelings of fear and anxiety. So way too much GABA could presumably make
someone feel fearless — like how severely infected mice seem to be less afraid of cats,
and get eaten more often. That way, the parasites can continue their
life cycles. But even with all this research, other studies
have suggested there isn’t a significant association between toxoplasmosis and mental
disorders. A study from Duke University took blood samples
from just over 800 people to look for T. gondii antibodies, and did other surveys and tests
to collect data about their behavior. About 28% of their participants tested positive
for parasite antibodies. But the researchers didn’t find a significant
association with schizophrenia, depression, or other mental disorders, or any link to
impulsive activities like crime or car accidents. So research in this field is tricky, because
animal models like mice aren’t entirely comparable to humans. But it’d also be super unethical to do controlled
experimental studies on humans, like giving people toxoplasmosis and monitoring their
brains. But, there is no reason to ditch your cats. They bring happiness and cuddles! There is so many positive health outcomes
associated with having a fuzzy thing in your house. Just be careful around their poop, like, make
sure it doesn’t go in your mouth. Try to keep them from eating mice and birds,
if that’s possible. And make sure your food is cooked properly
so you don’t accidentally eat any uncooked parasite eggs. Thanks for watching this episode of SciShow
Psych, which was brought to you by our patrons on Patreon.

100 Replies to “Toxoplasmosis: How Parasites in Your Cat Can Infect Your Brain”

  1. Dont let your cat eat a bird or a rat cause after they eat the dead animal lol toxoplasmosis all over its mouth and after they lick their entire body and you pet them and now your infected!!!

  2. 4:40 Wake up people, this man is infected, the parasite is controlling his brain and using him to spread prejudice.

  3. Toxoplasma gondii may be linked to chronic depression. The immuno-response that it elicits from the body ends up directly degrading Tryptophan through NK Natural Killer cells, Tryptophan being something Toxoplasma gondii depends upon to survive. Degradation of Tryptophan is not only linked to depression but also Schizophrenia.

  4. I thought Toxo eats GABA resulting in too much glutamate (go signals) leading to the fearlessness.
    Meaning, GABA is the foundation of discretion, yes, but it's complicated.

  5. My cat wipes his behind on the carpet so I’m screwed… not that I lick the carpet, at least I don’t lick my ass…. annnyway

  6. Way to much info at once. I understand exactly what you’re saying but people that need to really know this because it is really really important it’s going to be difficult for them to understand what you’re saying because you’re all over the place new talks so fast

  7. In Russia it's common to "throw out" your cat when you are expecting a baby because of the fear of infecting the baby.

  8. I just got into an argument with someone about T Gondii which snowballed, involving more people all saying T Gondii was a mind controlling parasite.  I disagree and am trying to explain that in order for the parasite to mind control something it must have an intelligence of its own, to make its subject do its bidding.  What im saying is, it is a mind altering parasite, simply reacting to environment and causing chemical in the creature it is inhabiting.  not an evil invading monster intent on controlling animals or people.  Am I right or wrong about this? are they intelligent  and are they mind altering or mind controlling?

  9. I hate how these videos drag out on the information, also a video uploaded by a university in Sweden says its just 20-25% and that the only ones getting symptoms are people with a low immune system (explains why he says the symptoms would be like a mild flu)

  10. And don't try to make a field cat, a house cat. The doctors never knew, but I finally know what my cat might have been sick from (had to put him down from it). I think I have the human symptoms too… I'm otherwise fairly healthy, should I get checked for it? Will the immune system deal with them?

  11. Colloidal silver safely kills toxoplasmosis in humans and animals. https://m.facebook.com/Colloidalsilverguy/posts/1615136488724690

  12. I'm a middle aged man who's been around cats since literally the day I was born. If anyone has toxo, it's me. Still waiting for that extra dopamine and gaba to kick in.

    Edit: This video fails to mention that when a cat acquires toxo, their poop is only contagious for a couple of weeks. Yes, the toxo lives on (dormant) in the turds for several months, but assuming you scoop the box every few days, the exposure from your cat is over quickly.

  13. I knew there was something fishy about those darn felines. I always knew those cats were always trying to take over the world, and shhhiet

  14. My girlfriend has a weird uncle that I used to hate but then found out he suffered from toxoplasmosis and Brian cancer poor guy

  15. Why do people always focus on cats when they're only infectious for a couple of weeks and ignore the fact that rare lamb, at any stage of its life, can also give people toxo, so is far more likely to infect people? Do people fear a backlash from the sheep grazing industry?

  16. My cats eat what ever meat I cook for myself. One is 20 in human years and has never had a wild animal or packet food and yet he still runs around with my youngest who's 6 human years

  17. well, cats are friggen gross, hey , let's get an animal that paws in it's piss and feces and walks around our house after.

  18. Awesome video, thank you so much. Please keep animals in perspective. Keep your wife, keep animals out in the woods.

  19. “Be careful around your cats… like make sure their poop doesn’t get into your mouth.”

    Hey, Mr nosey, mind your own business.

  20. Cats swipe their feces – to cover them in the litter box. The feces are coated with eggs. Eggs get on the paws and between them, and are next transported throughout the human living environment. Having cats on your bed, furniture, countertops is particularly beneficial towards being infected. Mental effects of Toxo are looking more and more credible.

  21. Think of it this way cat made us fearless this parasite made the modern world.with out it we would still be hiding in caves

  22. I say test
    "Remain-iacs" (#Brexit)
    "Refugees welcome" libtards.

    Anyone with zero threat awareness of inviting millions of 3rd worlders into the West!

  23. This parasites make rats feel atracted to cats, could this parasites also influence human sexual orientation? Some people say yes. Look it up.

  24. I am a student in a laboratory that studies Toxoplasma gondii, I believe that the most recent hypothesis for how does the parasite induce behavioural changes is that a low-level brain inflammation is involved. The tyrosine hydroxylase does not seem to play an important role. I will link some papers tomorrow.

  25. That's it. Ban cats. Time to build meowschwitz and start exterminating every goddamn last one of those monsters.

  26. There is zero chance that I don't have this condition. I will get tested. But I already know the truth….some call it a "parasite" but I call it <evolution> get on our level non-cat lovers!

  27. No teacher tried to teach this in school over this country. And I know one of the most popular of my/our school teachers fed her cat milk every day. 1+1= algebra.. EH? Speaking of bra's; hers were…

  28. Actually this is largely false. A humans immune system has to be extremely compromised to get this. This showed up in an early
    A.I.D.S. Patient. Same with an A.I.D.S. Patient developing a "Sheep's" disease. So this is just b.s. really

  29. there's acually a series of books from norway where basically this parasite gets mutated in the nuclear meltdown in japan in 2012, where it basically turns people into zombies that, when they've been aggressive and deadly for a while, just start being incredibly passive so that they can die and therefore spread the parasite even further. It's called "I morgen er alt mørkt"/ Tomorrow everything will be dark.

  30. Diabetics & Cancer patients have a extremely low immune system!!! So no pets for me, no way!!!🦠🐈🙏🐕🦠🐱🦠🐶🦠🐾🐾🦜🦚🦉🦢🦆🦅🕊🐧🐦🐥🐤🐣🐓🐔🦃🦠🦠🦠🦠🦠🐹🐀🐁🐭🦠🦠🦠🦠🦠🦠🦠🐃🐂🦠🐑🐏🐇🐰🦠🦠🦠🦠🦠🦠🦠🦠they all carrie Parasites , Cook your Meat & Fish & Sea Food completley done never eat raw meat even your Burgers, & Steaks no raw meats & eggs some Chefs leave a red line in their Hamburgers & Steaks, "raw meat can make one sick, & you can die".
    Orah did a show on what Raw Meat does to people!!! Watch her show!!!
    I wash my hands with "Dial White", its the best Antibacterial Soap for your Hand Washing!
    I know a Doctor that wont let his daughters & Wife was their hands with anything except "Dial White".
    My Husband isnt a Hand Washer, & he is sick as hell right now with Diarrhea!!! & everytime he eats he gets Diarrhea he crapped his pants 3 times today!!! He cleans the Kitty Pan, the Kitty has Diarrhea too!!! My Husband rescued this Kitty out of the Mennonites Barn, that Mennonites Son feeds them Barn Kitty's left overs from their Dinner, churned butter peas carrots meat potatoes, milk mixed into it, and they give the Barn Kittys Cows raw Milk non Homogenized Milk.
    The Vets always saw Milk & Human food slows a Kittys growth down by 8 whole days!!! So if you rescue Barn Kittys be extra Careful.
    My Husband can die from this little Kitten passing a Parasite onto him he says, hes depressed & scared & mad

  31. I have three cats and I've long known about this parasite. However, there is nothing you can do to prevent being infected by it if you have a cat. Cats bury their poo in litter with their paws. They then use their paws to clean themselves ALL DAY. You then pet your cat. Then you forget to wash your hands because no sane person would wash their hands every time they petted their cat. Boom you now have the infection.

  32. As long as you clean the poop before it has been 24 hours since the poop was made, the toxoplasmosis bacteria have little time to get into their infects stage

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