UKC

So I was browsing papers just now and I stumbled across this:
http://www.scientificamerican.com/article/common-parasite-linked-to-persona...

A paper published in Nature showing how a microscopic parasite, which infects 22.5% of the American population, has been found to increase reckless behaviour and make hosts less conscientious.

How many outdoors people, and climbers specifically, do you think have this (I would guess it's higher than in the normal population) and would you say those people who push their grade hard are even more likely again to have this? The paper shows that people who have been infected for a longer time are proportionally more reckless.

Interested as to what other people think!


"Feeling sociable or reckless? You might have toxoplasmosis, an infection caused by the microscopic parasite Toxoplasma gondii, which the CDC estimates has infected about 22.5 percent of Americans older than 12 years old. Researchers tested participants for T. gondii infection and had them complete a personality questionnaire. They found that both men and women infected with T. gondii were more extroverted and less conscientious than the infection-free participants. Toxoplasma manipulates the behavior of its animal host by increasing the concentration of dopamine and by changing levels of certain hormones”

"In the new study, a pattern appeared in infected men: the longer they had been infected, the less conscientious they were. This correlation supports the researchers' hypothe-sis that the personality changes are a result of the parasite, rather than personality influencing the risk of infection."

In reply to Morgan P:


Sounds like a load of rubbish

In reply to Michael Gordon:

Good expert opinion there.

In reply to Michael Gordon:

I think the fact that it's been published in one of the two most prestigious scientific journals in the world (Nature and the other being Science) would suggest otherwise!

In reply to Morgan P:

Where is the Nature article link - the article you link to in Scientific American refers to the European Journal of Personality, which is perhaps a little more obscure....

(Apologies if I've missed the blindingly obvious!)

In reply to davidbeynon:

So what do you think would be the basis of Morgan's "expert opinion" that pushing one's grade in climbing has some kind of connection with "recklessness"? "Load of rubbish" strike me as quite polite.

In reply to Morgan P:

It's been known for years!

In reply to Morgan P: Sounds similar to Dicrocoelium Mind Control, where the parasite controls multiple hosts to suit it's own life cycle


"The lancet liver fluke, Dicrocoelium dendriticum, is commonly found in the liver and bile duct of grazing mammals such as sheep and cows and has a complex lifecycle, requiring several different hosts throughout ontogeny. They first infect terrestrial molluscs, such as snails, which leave behind slime trails that are ingested by ants, the second intermediate host.

Interestingly, behavioural changes observed in infected ants appear to enhance the parasite’s transmission to its definitive host, grazing mammals [5]. The parasite larvae infect the brain of the ants and encyst in the subesophageal ganglion (Figure 1) [6]. This area of infection is adjacent to the mandibular nerves, which explains the observed behavioural changes of the ants. The effects of behaviour manipulation are most apparent at night, when ants climb to the top of a blade of grass and bite down (Figure 2). The ants bite down on the grass because of the tetanus caused by the infection [5], and become immobile until dawn. This renders the ants very susceptible to accidental ingestion by grazing cattle or sheep, in which the D. dendriticum reproduces and completes its lifecycle."

In reply to Carolyn:

Hey, sorry I tried to post the Nature article first but, because I was logged in on my university account and so had access, I couldn't get the link to work when I posted it as it assumed access to the full article which most people wouldn't have.

...However, while writing this reply I just noticed I was wrong about it being in Nature. I skim read and assumed that, as it was on Nature.com that meant it was the Nature journal, not a website called Nature! Oops..

However, I mean it's still a published paper, just not from *Nature*.

In reply to AlanLittle:


That isn't my expect opinion at all. I was making a hypothesis about it: As this parasite is so common and increases recklessness, it seems that concept of grade pushing (specifically on dangerous routes that require a degree of recklessness and lack of fear) *could* be more likely among people affected by this?

It's unlikely to have a big effect, I'm just hypothesising and thought the article was interesting so would share.

In reply to Morgan P:

"Feeling sociable? You might have toxoplasmosis".

Snigger.

So, because something is a published paper you automatically give it credence? Oh dear, all that money on a university education etc etc

In reply to AlanLittle:

The connection between toxiplasmosis and risk seeking behaviour has been known about for over 20 years. It's a big part of how the parasite reproduces in the wild after all.

If you can't see the connection between reckless risk seeking and a substantial subset of climbers then you aren't looking.

In reply to Morgan P:

hmmm..... http://www.tylervigen.com/

In reply to nw:


Definitely not 'automatically'. However, as others have posted describing, this reckless behaviour has been observed and proved in other creatures already. It is only a step further to see it in humans and thus I'm inclined to believe the paper.

In reply to Morgan P:
I actually work on Toxoplasma (sometimes).

There is a definite link between Toxoplasma infection and reckless behaviour in mouse models.

The evidence of this being true in humans is circumstantial at best. There are anecdotal stories of rapists/murderers/joy riders being infected with Toxo, but often no-one actually knows how long these people have been infected for or whether the infection can be definitively linked to their behaviour. On the other side of the coin, given the infection rate in humans, there must be plenty of people out there who are infected who don't suddenly get the urge to steal cars and go joy riding, or push themselves climbing.

My own thoughts are that it is possible that behaviour changes induced by Toxo infection occur in humans, but far from proven. If this phenomenon does exist, it is likely that certain individuals, perhaps those who already have behavioural problems or mental health difficulties, may be more susceptible.

As for whether more climbers are infected, I don't think that would be the case. The main route of Toxoplasma infection globally is through eating infected meat (usually pork), although in the UK this isn't really a problem. In the western world, it is actually cat-owners who are most likely to be infected as Toxoplasma is transferred in cat faeces.

Edited to add: I've just done a quick literature scan and found several papers showing that antibody titres against Toxoplasma are higher in patients presenting with schizophrenia for the first time than in the general population, so there is a possible link there. Not sure this would equate with reckless climbing behaviour though...

In reply to kathrync:




That's really interesting, thank you for the input! Just to confirm, I wasn't saying that this would be a primary (or even secondary) cause of any behavioural traits, simply whether it has a statistically non-negligible influence.

You're definitely right that a positive correlation is easy to get a false positive with if you're only looking at those who are risk-takers and then check them for infection rates.


True, it would be interesting to see some studies on this


It would seem that if it had a significant impact, you're local neighbourhood cat-ladies would be the most prominent partakers in a whole host of adrenaline-fuelled adventure sports!

Thanks for the intelligent input!

In reply to Morgan P:

You want to be careful visiting websites with "nature" in them. In the early days of the Internet I made the mistake of searching for "nature magazine" looking for the scientific journal...

In reply to kathrync:



A quick pubmed search also shows a higher than expected seropositivity in people dying in motorcycle crashes. Clearly not all such accidents are the biker´s fault, but it probably as good a proxy for reckles behaviour as you are going to get (one can at least reasonably assume that on average the surviving bikers were more careful).

Given that there are reasonable links between infection and behaviour in rodents, some ideas about the mechanism, and a clear evolutionary benefit for the parasite it is probably safer to assume that such a link also exists in infected humans.

Whether this would be big enough to be detectable in climbers, who knows. Probably a more clearly "reckless" subgroup might be required, maybe people who died soloing.

In reply to Morgan P:

Sorry but I think your hypothesis is garbage.

Firstly, only a tiny minority of "those people who push their grade hard" do so on dangerous routes. Secondly, most of what I've read and heard from that tiny minority suggests anything but "recklessness and lack of fear". Heave you read (e.g.) the chapter on headpointing in Dave MacLeod's book?

You need a bit more than "that looks scary to me, therefore the people who do it clearly don't know the meaning of fear".

In reply to cb294:




Yes, I don't disagree with anything you say there. The big problem in humans is that you can't just go around infecting them and looking at behavioural traits before and after so all the evidence is always going to be circumstantial. There are one or two people who work in the field who have infected themselves, but the sample sizes are too small to do much with. Given that, I am always going to use language such as "it is possible..." or "it is probable..." in this case rather than stating it as fact

In reply to kathrync:


Fascinating stuff. Would I be roughly right in guessing that the parasite just prefers a certain region of the brain to live in and destroy that has an influence on impulse control? I've heard stories of people who've had brain lesions that have led to impulsive (criminal) behaviour before.

I would be very skeptical of links to the types of risk-taking associated in climbing which are considered assessments of risk vs competency, rather than a failure to control an impulse. I doubt anything could or would evolve to attack the subtle brain circuits involved in evaluating risk which are presumably much more diffuse throughout the the cortex than some more primitive lump of brain tissue that toxo makes its home in.

In reply to Jon Stewart:


To be honest, I don't actually know that much about this aspect of things - I am primarily a genome analyst and evolutionary biologist. Toxo happens to be one of the species I work on at the moment so I have done some reading about it, but I don't know much about the neurological aspects of this.

In reply to kathrync:

Righto. I'm not sure we have any neurologists on UKC, which is a shame as I've got lots of questions for one...

In reply to kathrync:

The magazine article has:

“Toxoplasma manipulates the behavior of its animal host by increasing the concentration of dopamine and by changing levels of certain hormones,” says study author Jaroslav Flegr of Charles University in Prague, Czech Republic.

So it isn't a brain lesion thing at all. Amazing.

I also had no idea that it was common and usually harmless to be infected with toxo, I thought it was something we should really avoid, given what it can do to the retina for one thing.

In reply to Jon Stewart:

At least in male rats, latent infection is thought to stimulate brain regions associated with sexual arousal. Probably this is not the only target, mice, and IIRC especially female mice, seem to exhibit increased curiosity and a liking for cat urine.

Probably rather complex. The sitation is apparently more clear in some parasites that reprogram insect behaviour (e.g., make an ant climb to the top of a leaf and lock itself there by a fixed bite), where the activity can be mapped down to a few affected neurons.

However, neuroparasitology is not my specialty, it is just one of the cool things I try and keep up with at review level. Stuff like this made me study biology in the first place!

CB

In reply to Jon Stewart:



Yes, this is actually quite a common infection model, although it's more common in viruses than eukaryotic pathogens. It is often advantageous for a pathogen to be asymptomatic as it can then reside in the host for a long time and potentially has more opportunity to infect new hosts.

In reply to davidbeynon:

Sorry, I didn't realise he was just looking for opinion from experts

In reply to Morgan P:


Neither of which say anything about climbing, of course. It's nonsense because (a) climbing has very little to do with recklessness, nor do climbers tend to be more extroverted than the general population, and (b) even if the above was untrue, correlation does not equal causation.

In reply to AlanLittle:

I used to solo close to my limit occasionally when I was younger, have become significantly more reckful since. And yet I detest cats. Hmm, strange.

I don't think we need to look much further for a correlation than testosterone.

In reply to AlanLittle:

Or just that people enjoy climbing and therefore sometimes decide to rise to the challenges that the activity presents?!

In reply to Morgan P:

I have always been very skeptical about the degree to which Toxo affects behaviour, mainly due to the fact that authors are often way too willing to make sweeping statements on the implications of such a widespread parasite negatively affecting behaviour of humans. I have even seen authors specify differences in the way Toxo affects men to women, there is nowhere near enough evidence for claims such as this even assuming the correlations are objective and not highly subjective.

I can see the logic, Toxo is fundamentally a behaviour altering parasite, altering the behaviour of the intermediate host (mouse) to be attracted to cat urine so it is more likely to be eaten and therefore enter the definitive host (cat) to complete its life cycle. But the only problem is parasites are notoriously specific in the hosts they infect and how they affect them, so this doesn't convince me it has an effect on human behaviour at all (my job would be a whole lot easier if parasites were that simple).

In short, there is not enough evidence to suggest that there is any correlation and the data that is available is far from objective. Weirdly, this is the most common question I get when I tell people I'm a Parasitologist...