Effects of Toxoplasma on Human Behavior (2007) | Hacker News Reader

Effects of Toxoplasma on Human Behavior (2007)

ncbi.nlm.nih.gov

55 pointsPaulHoule26 comments

From the abstract

> ...the personality of infected men showed lower superego strength (rule consciousness) and higher vigilance. Thus, the men were more likely to disregard rules and were more expedient, suspicious, jealous, and dogmatic. The personality of infected women, by contrast, showed higher warmth and higher superego strength, suggesting that they were more warm hearted, outgoing, conscientious, persistent, and moralistic. Both men and women had significantly higher apprehension compared with the uninfected controls.

I don't have the expertise to judge the quality of this study, but that's a fascinating conclusion

It reads like a horoscope and it is worth as much.

Toxoplasma research is pretty established and the conclusions above matches fairly well what I learned 20 years ago.

https://en.wikipedia.org/wiki/Temperament_and_Character_Inve...

It's based on yet another psychological framework, with the same underlying flaws in methodology that plague the MB model, which the "big 5" model tries to correct for with better statistics.

Any framework can have value, and it's unnecessary (and incurious) to dismiss this study as a horoscope. The findings are consistent with most other literature on toxoplasmosis.

Could be that men and women have different responses to disease burden. Makes sense that men increase risky behaviour to make the most out of the last days of his life, women try to fit in even more than before to not get kicked out of the group and thus maximize chance of survival. Toxoplasmosis might make the body think it is dying and thus induce this forever even though it isn't dying.

For anyone curious about treatment for latent toxoplasmosis, this was an interesting read: https://journals.asm.org/doi/10.1128/mBio.00381-19

I’m a former practicing veterinarian, had 13 outdoor cats as pets as a child and several indoor cat pets over my life, and so almost certainly am in the 1/3rd of humans who are infected/affected.

As a person affected, have you taken Guanabenz/Wytensin?

Nope.

> Unexpectedly, guanabenz caused nearly half of the chronically infected mice to die within the first 10 days of drug treatment (Fig. 6B). Mice that succumbed to the guanabenz treatment developed classic symptoms of Toxoplasma encephalitis, including lethargy, tremors, paralysis, and seizure. None of these mice showed signs of active infection at the start of guanabenz treatment. These results suggest that the mice experienced reactivation of encysted parasites rather than continuation of a severe acute infection, but we cannot rule out the presence of lingering tachyzoites at the start of drug treatment. The mice that survived the full drug treatment did not display any symptoms of Toxoplasma encephalitis.

So in this case reactivation allowed the immune system to fight and destroy the infection (for those that survived). I don't really understand the part in the abstract about there being a reduction in symptoms despite no reduction in cyst burden (that this was not necessary for a response). Could someone explain?

I am skeptical-but-open on the behavior-alteration hypothesis, but I do think it’s worth dropping in this paragraph from the Discussion. Getting around it will take some really clever experimental design.

> Alternate explanations for the effects of T. gondii on humans cannot be ruled out. It is possible, eg, that individuals with certain personality characteristics behave in a manner that makes it more likely that they will become infected.

This is always a given, though – correlation vs. causation. It's good that it's mentioned, though.

Or indeed, are we people with certain personality traits more likely to have cats (and therefore much more likely to be infected)?

Don't forget Baylisascaris procyonis, the roundworm in raccoon droppings that eats your brain. I found out about it a decade ago, when someone told me about the roundworm in raccoon droppings that eats your brain, after I had just cleaned up a beachball-sized latrine of raccoon droppings that was killing our tree:

https://en.wikipedia.org/wiki/Baylisascaris

So ya, stay away from the roundworm in raccoon droppings that eats your brain.

Thanks for the thought.

FWIW ivermectin kills these roundworms.

Stanford neuroendocrinology researcher Robert Sapolsky Explains Toxoplasmosis. Utterly fascinating.

https://m.youtube.com/watch?v=NroiGfNohPo

An old roommate used to work at a lab that also researched this stuff. Similar conclusions, or at least strong signs of some impact on humans, if I recall correctly

Ah well, still going to keep my cats

What you meant was: You're not trying to escape them, right? After all, some cats have humans, not the other way around.

If you want to see sophisticated technology - look no further!

> the parasite changes the behavior of the rodent in such a way as to increase the chances of the parasite's getting into a feline and completing its life cycle

Seems like it is working as intended!

It’s not the only parasite I’ve shared with my cats.

Also: https://www.economist.com/science-and-technology/2010/06/03/...

> Published online 2007 Jan 11.

Past related threads. What doesn't it do?

Toxoplasmosis associated with entrepreneurial initiation and performance (2020) - https://news.ycombinator.com/item?id=28988486 - Oct 2021 (55 comments)

Increased risk of traffic accidents in subjects with latent toxoplasmosis (2002) - https://news.ycombinator.com/item?id=28424007 - Sept 2021 (61 comments)

Toxoplasma – The Most Successful Parasite in the world (2018) - https://news.ycombinator.com/item?id=27870034 - July 2021 (6 comments)

Toxoplasmosis: An important risk factor for acquiring SARS-CoV-2 infection - https://news.ycombinator.com/item?id=27870025 - July 2021 (77 comments)

Toxoplasmosis: The Cat Poop Parasite That's Probably in Your Brain - https://news.ycombinator.com/item?id=27615857 - June 2021 (37 comments)

Toxoplasmosis – A Global Threat (2014) - https://news.ycombinator.com/item?id=27599085 - June 2021 (54 comments)

Scientists find link between infection with Toxoplasma gondii and schizophrenia - https://news.ycombinator.com/item?id=19042800 - Jan 2019 (1 comment)

Risky business: linking Toxoplasma infection and entrepreneurship behavior - https://news.ycombinator.com/item?id=18762544 - Dec 2018 (30 comments)

Mind-altering parasite spread by cats could give humans more courage - https://news.ycombinator.com/item?id=18000109 - Sept 2018 (1 comment)

Toxoplasma gondii may help promote the entrepreneurial spirit? - https://news.ycombinator.com/item?id=17615209 - July 2018 (4 comments)

Rage Disorder Linked with Toxoplasmosis (2016) - https://news.ycombinator.com/item?id=15376654 - Oct 2017 (66 comments)

Having a Cat Does Not Cause Mental Illness, New Study Suggests - https://news.ycombinator.com/item?id=13709169 - Feb 2017 (41 comments)

Is there association between Toxoplasma gondii infection and bipolar disorder? - https://news.ycombinator.com/item?id=13048748 - Nov 2016 (13 comments)

The Relation of Toxoplasma Infection and Sexual Attraction to Fear, Danger, Pain - https://news.ycombinator.com/item?id=12335134 - Aug 2016 (49 comments)

Toxoplasma gondii – 30 to 50% of humanity has a brain parasite - https://news.ycombinator.com/item?id=12011197 - June 2016 (3 comments)

Toxoplasma Could Manipulate Our Behavior - https://news.ycombinator.com/item?id=9269688 - March 2015 (23 comments)

Toxoplasma infection permanently shifts balance in cat-and-mouse game - https://news.ycombinator.com/item?id=6411785 - Sept 2013 (8 comments)

Cat parasite toxoplasma uses 'Trojan horse' to infect human brain - https://news.ycombinator.com/item?id=4888086 - Dec 2012 (1 comment)

A game of cat and mouse: Evidence that Toxoplasmosis may affect human behaviour - https://news.ycombinator.com/item?id=1420315 - June 2010 (4 comments)

The parasite Toxoplasma makes rats lust for cat pee and people drive motorbikes - https://news.ycombinator.com/item?id=1405479 - June 2010 (24 comments)

Robert Sapolsky discusses Toxoplasma's effects on mammalian behavior - https://news.ycombinator.com/item?id=1052855 - Jan 2010 (3 comments)

Giant Plush Microbes - Toxoplasmosis, Gangrene, Etc. - https://news.ycombinator.com/item?id=577409 - April 2009 (3 comments)

Cats, the original supercarrier.

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