Toxoplasmosis: An important risk factor for acquiring SARS-CoV-2 infection | Hacker News Reader

Toxoplasmosis: An important risk factor for acquiring SARS-CoV-2 infection

medrxiv.org

91 pointswalterbell77 comments

This is interesting, but I don’t believe the study should be trusted. The authors determined toxoplasmosis status by asking the participants. This seems like it will introduce huge bias based on the bizarre subset of people who know their status.

A similar study that tested for toxoplasmosis antibodies would be much more useful.

I agree it should not be taken as definitive. However, I do think it makes sense to have done this first, since it provides a relatively quick and low-cost way of finding out if there is anything that justifies a more expensive and time-consuming investigation (that yes, should involve a test of toxoplasmosis antibodies).

It appears that the answer is yes, it justifies such a study.

The authors addressed this issue at least somewhat:

"Toxoplasmosis status was self-reported by respondents, which may be viewed as a drawback. On the other hand, it has previously been demonstrated that information on toxoplasmosis status provided by 3,827 participants of another internet study nearly perfectly (99·5%) corresponded to information in our files on subjects tested for toxoplasmosis in our lab."

That doesn't make any sense: the CDC claims "in the United States it is estimated that 11% of the population 6 years and older have been infected with Toxoplasma" and Wikipedia claims "serological studies have estimated that 30–50% of the global population has been exposed to and may be chronically infected with latent toxoplasmosis"... and yet, other than pregnant women, does anyone ever get tested for it? The CDC even goes so far as to directly claim "most people who become infected with Toxoplasma gondii are not aware of it because they have no symptoms at all"!

Presumably, they tested a representative sample at some point and extrapolated

Like the various health authorities in the US tested a representative sample for Covid RNA, antigens, and antibodies to determine unbiased population level data?

/me runs.

You run, but it’s pretty obvious one reason that never happened is because you can use the phrase “best available evidence” to do whatever you want when you control the funding for evidence gathering.

That’s unnecessary. The CDC and the WHO are perfectly willing to make statements that contradict the best available evidence even without deliberately suppressing the production of better evidence. It’s easier to just ignore the evidence.

(I don’t think this is malice. A combination of being unwilling to admit mistakes and simply not being very good at one’s job seems more than adequate to explain this.)

Extrapolated what? I am taking what the CDC is saying here as truth, at which point it seems almost impossible that 99.5% of people would know correctly if they have toxoplasma... it would seem like your accuracy on guessing that should be extremely low. (FWIW, I am guessing that you somehow failed to read the context of the conversation and are saying the CDC tested a sample of the population and extrapolated the number of people who have it... "duh".)

So people who were tested for toxo knew they had it? Scratches head.

That’s not exactly the same issue though. The issue was that the subset who know their toxoplasmosis status is probably not representative for the population at large. This remains a potential problem even if they are perfectly right about their status.

Perhaps people that do know they have Toxoplasmosis, know for sure; but many people have it do not know.

So maybe the risk factor here isn't having Toxoplasmosis, but knowing you have Toxoplasmosis :-) (or more seriously: some other factor correlated with it, like being a veterinary or animal handler which may be required to test regularly)

How can that be possible? 99.5% accuracy in knowing status? That's absurdly high, considering, just for a start, more than 0.5% of people have cognitive disorders that would interfere with accurate surveying.

And how many of those 3827 Internet study participants got tested?

(2018) https://bohembaeksvensson.medium.com/toxoplasma-the-most-suc...

> Toxoplasma is the most “successful” parasite in the world but known only to a few. In humans, it infects the brain, heart, lungs, and muscle tissue ... Toxoplasma is being associated with depression, cancer, diabetes, obesity, bipolar, schizophrenia, self-harm, dementia, aggression, reduced learning ability in children, subtle mind-control, and impaired curiosity. It has infected more than 30% of the global population ... The older you are the higher the probability of being infected. If you are 50 years old, the average probability of being infected with Toxoplasma is in the range of 50% — so it’s worth investing 15 minutes in getting to know it.

(2017) https://labblog.uofmhealth.org/lab-report/how-to-stop-lurkin...

> Undercooked meat can spread Toxoplasma bradyzoite cysts, and the parasite is often transmitted to humans through cat feces that contain another cyst form. That’s why public health authorities advise pregnant women not to change cat litter boxes, and advise anyone who eats meat to consume it only fully cooked. The key danger from toxoplasmosis is that it’s one of the few infections capable of crossing the blood-brain barrier. That means it can get into the nervous system, including the retina, spinal cord and brain. It can also hide out in muscle tissue of both humans and animals.

If youve ever known people that have been traumatized by their health or experiences, they like cats to keep them company because they give oxytocin, are really chill and don't require a lot of upkeep.

I don't see how it isn't obvious which way the causality is swinging. Toxoplasmosis isn't causing this great variety of symptoms, that makes no sense. It's more like people with a great variety of symptoms use cats to cope with life.

Also, doesn't this #1) only happen to outdoor cats, and #2) emit from them once in their life if they ever get it?

My understanding is yes to both, but I can currently only find a citation for #1: https://www.cdc.gov/parasites/toxoplasmosis/epi.html (strictly speaking, the cat must eat an infected pray, so a domestic cat could get this if it hunts)

You make a strong argument for recreational cat use, but I can't say I'm fully convinced.

lol

That's true. Moreover, it could be a gateway pet.

Definitely a gateway pet. I've started using dogs now.

Psh. Everyone knows by now that the gateway theory is utterly debunked. Some people start with cats, some people start with dogs, not everyone ends up using both, and some quit the pet trap altogether - for example, if their new partner does not like the smell of cat piss.

The only reason cats look like a gateway pet is because the same dealers sell both cats and dogs - and everything up to venomous tarantulas and constrictor snakes. And you bet they make a better profit off the more dangerous pets, because you need more equipment to use them on a day-to-day basis.

The feds let it happen because eventually all retail chains get a chunk of the sales. Food, enclosures, electronicals, silicone sealants, plastic containers, special furniture, all bought with hard-earned cash that could have chosen otherwise.

Pets are the real matrix.

I'm still only using cats but I use two now to get the same boost as one a decade ago.

To my mind, as someone who isn't a pet person, that's potentially a useful perspective to keep in mind when trying to sort this out. But I don't think your observation is something we can say confidently disproves the idea that toxoplasmosis contributes to a variety of other health issues.

It's possible that it's a little of column A and a little of column B rather than either/or. People tend to want to "pick one" (and only one) and that's often a poor way to try to sort out what's really going on.

We really ought to find a way to cure a latent infection of Toxoplasma gondii. I wonder if CRISPR could do it.

If we cured toxoplasmosis, then there would probably be a ton of abandoned cats.

I don't follow your logic here...care to elaborate?

I think the joke the OP is making pokes at the parasite's "mind control" abilities; i.e. that it's somehow controlling the human mind to think cats are cute.

I wonder if it was the reason for the worshiping of cats in ancient Egypt [0]

[0] https://en.wikipedia.org/wiki/Bastet

Probably not, but I mean... who knows?

Minor alterations in human behavior over time eventually venerating our feline friends?

Yes but it's not a joke, it's an inference.

If I take it less seriously than intended, it's a joke.

The most common way to get infected is from cats. Specifically cat feces.

IIRC toxoplasmosis affects the brains of rodents making them less afraid of cats, which means that they're more likely to be killed and eaten by those cats, which spreads the infection to the cats. I think there have been claims that perhaps it also makes infected people like cats more in a similar fashion, which I guess is what GP is referring to.

Not the OP. Toxoplasmosis from what I understand can cause mice to lose fear of cats. So I think what the OP is suggesting is that toxoplasmosis is brain washing us to like cats and without it we would abandon some cats.

I thought it was associated with higher risk taking. The mice are less fearful in general, hence they may take risks that make them more likely to be seen/caught/trapped/eaten by the cat.

There's a story about a doctor (I think) who started to have a sixth sense for ordering toxo tests for people who came in to the ER with motorcycle injuries. The tests often came back positive. IIRC the high positivity was due the fact that toxo increases risky behavior in humans as well as mice.

It's still an open question why mice with toxo don't end up in hospital for motorcycle injuries. I have an inkling that it is correlated with the low rate of human toxo victims eaten by cats each year, but who knows.

Hey dang-- why is sibling comment by SandMan2233 flagged? It's a funny response to my tongue-in-cheek questions at the end of my comment.

I get it if someone wants to downvote a joke. But flagging is extreme, and I thought the upshot of your moderation system was to temper extremism.

Toxoplasma changes behaviour, GP is implying (likely facetiously) that liking cats is an influenced behaviour by the parasite.

We only have broad suspicions how behaviour affects humans, with different effects for men and women.

There is a theory that toxoplasmosis infection causes humans to acquire more cats. The analogy is that mice infected with it are more likely to be consumed by cats because they appear to have a lower fear response to felines

Last I checked, toxoplasmosis was curable:

>Most healthy people recover from toxoplasmosis without treatment. Persons who are ill can be treated with a combination of drugs such as pyrimethamine and sulfadiazine, plus folinic acid. [0]

Or is there something special about a latent infection vs an active infection?

[0] https://www.cdc.gov/parasites/toxoplasmosis/treatment.html

The latent infection forms cysts in the brain that remain for the rest of the life of the organism. These cysts cause the behavior changes in rodents that attract them to the smells of cats.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC106833/

"[The cysts] are more prevalent in the neural and muscular tissues, including the brain, eyes, and skeletal and cardiac muscles. Intact tissue cysts probably do not cause any harm and can persist for the life of the host without causing a host inflammatory response."

> forms cysts in the brain that remain for the rest of the life of the organism

where organism = mouse. We are neither mice nor live for one year and then die like mice do.

If you read the paper, you will discover that the infection is indeed life-long in humans.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4116007/

     Conclusion:

     These results indicate that ivermectin 
     significantly inhibited replication of 
     the tachyzoites of Toxoplasma gondii RH strain.

Thanks for this lab data point.

The treatment for toxoplasmosis is the focus in this article.[0]

[0] https://news.ycombinator.com/item?id=11037196

Knew not liking cats would be good for something someday.

(Most people get toxoplasmosis from their pet cats)

I wonder if this could be the reason Ivermectin seems to help with Covid.

It doesn't.

https://news.ycombinator.com/item?id=27852130

Hogwash, it helped me tremendously with long covid. Felt better in hours and then much better after a few days. I'm on prednisone now to finish off the last symptom, chest congestion/inflammation and it's getting much better on that.

Go and see a reddit forum on it and listen to thousands of others benefiting.

Just curious, and not trying to start a flamewar, but as someone who's just reading and trying to be better informed, how is this 3 minute old comment already greyed out? Would someone who has downvoted and perhaps sees what I might not be seeing about this post's personal experience care to explain why they think this is wrong?

N=1 is a fair criticism. But still.

The studies listed on this page are from reputable journals. Dig in. https://covid19criticalcare.com/ivermectin-in-covid-19/

Hello

https://www.theguardian.com/science/2021/jul/16/huge-study-s...

That study was apparently submitted by a blogger posing as a medical student.

There's 62 and counting other studies out there. I linked to some of them above.

When this is all over, I look forward to forensic investigations of fraudulent medical publications which had the effect of advancing or slowing specific political viewpoints.

E.g. one strawman submarine story can be used to drown dozens of legitimate stories. Or one flawed negative study requires 100+ doctors to object before the claims are withdrawn. We need to learn from these unfortunate incidents and improve our systemic defenses.

Fortunately, digital trails provide much data that can be used to build better defenses.

The problem with that study is that it's widely cited and powerful; it is apparently responsible for the majority of all attributed positive effect for ivermectin in meta-analyses. The fact that it's author was fraudulent doesn't mitigate that!

The link I provided discussed that study and its impact and claimed that it certainly doesn't reverse any meta studies.

I'm not sure we're talking about the same thing. Any meta-study that included the data from that paper has obviously been corrupted by it. And it was widely used in those studies.

Just by way of example, the FLCCC's comprehensive review article, which you cited favorably above, includes dozens of citations to the now-withdrawn Algazzar study.

Do "citations" affect the data? Citations are just for anti-plagiarism and for clout building, not science.

If they are studies that are performing meta-analyses (and most of the studies citing the fraudulent article are), yes.

Do meta analyses not control for the influence of outlier studies?

Could I just make up a phony result with 100000000x alleged effect and drown out all other studies in every meta analysis?

See the link at the top of the thread. That's more or less what happened here.

I didn't downvote -- the pro-ivermectin comments from swader999 are being made in good faith, and from what I can tell, the FLCCC's position is being held in good faith, too, not from a political or conspiratorial position -- but it's at least worth taking a look at criticisms of the FLCCC's methods that are out there. The big criticisms of ivermectin as a treatment for Covid-19 are largely criticisms of the way trials have been conducted. An actual quote from Pierre Kory, one of the FLCCC's founders, is, "We disagree with how most practice evidence-based medicine. We think they are way too biased toward randomized controlled trials."

https://www.medpagetoday.com/infectiousdisease/covid19/90552

And, it's possible that Dr. Kory's dislike of randomized controlled trials is in part because when they're run on his treatment methods, they don't seem to back them up: "Adults with mild Covid-19 who took a five-day course of the anti-parasite, tropical disease drug ivermectin showed no significant reduction in time to symptom resolution compared to patients taking placebo in a randomized, single-site clinical trial from Columbia."

https://www.physiciansweekly.com/covid-19-antiparasite-drug-...

The MedPage Today article notes that this isn't the first time this group of physicians' approaches have run into this "they think it works but the RCTs don't support it" problem, either. "Marik is known in the field for developing the HAT protocol for sepsis…a combination of hydrocortisone, ascorbic acid (vitamin C) and thiamine. His group's 2017 observational study of the protocol, published in CHEST, garnered excitement about the combination. But that hasn't been borne out in subsequent trials, including [names three studies]. Marik said the group adapted the protocol for COVID-19, using a more potent steroid and adding an anticoagulant, along with other elements."

So, this is controversial because they came up with a protocol for sepsis that hasn't been shown to work in randomized controlled trials, modified that protocol to treat Covid-19 in a way that so far doesn't seem to have been shown to work in randomized controlled trials, either, and are arguing that what this actually demonstrates is that randomized controlled trials suck. Maybe they're right, or maybe future RCTs will support this treatment as other doctors run similar trials. But, at slightly more than first glance, it seems to me that caution about ivermectin being a wonder drug in this context is warranted.

Lots of anecdotes vs peer reviewed research. I think I'll take the peer review thanks.

And that's what you should do. See the link above for decent studies. And really there is nothing else out there for long haul covid and ivermectin has been incredible for this group. Anecdotal evidence from an already proven safe and practically free drug is all we have right now.

The weight of peer-reviewed studies, once you exclude the most powerful one --- which has now been withdrawn --- is apparently that there is no positive effect on COVID19 with ivermectin.

Indeed. Here's a recent meta analysis[1] (discussed yesterday on the TWiV clinical update). Money quote: "In comparison to SOC or placebo, IVM did not reduce all-cause mortality, length of stay or viral clearance in RCTs in COVID-19 patients with mostly mild disease. IVM did not have an effect on AEs or severe AEs. IVM is not a viable option to treat COVID-19 patients."

High-power trials are needed to know for sure, but at this point the "true believers" (of which there are many) are operating much more on wishful thinking than solid evidence. It's still possible IVM will show some benefit, but I think at this point we can conclude fairly confidently it's not a silver bullet.

[1]: https://academic.oup.com/cid/advance-article/doi/10.1093/cid...

It could have helped you, or your anti-tiger rock might have functioned as expected. That's the trouble with individual data points.

Except for the fact that it actually doesn’t.

Only if you believe the WHO, which has been hacked at the highest level by other interests.

Blaming the WHO is what conspiracy theorists have been doing to drown out reputable people, who are debunking the ivermectin/covid19 hoax.

And it is a hoax - of the most egregious type. https://grftr.news/why-was-a-major-study-on-ivermectin-for-c...

grftr.news is a politically motivated site for attacking the right. I wouldn't trust it any more than I would trust the other side, e.g. breitbart and fox

Isn't there a difference between attacking with well founded facts, and attacking with opinions and lies?

There is, but that's not what I'm talking about. Regardless of how well researched and accurate their stories are, if they ignore half of the lies out there, they are carrying implicit strong opinion, and doing everyone a great disservice. The site rightly goes after people like Tim Pool and Andy Ngo, but I guarantee this site won't say a single word about the constant lies and misogyny of people like Cenk Uygur, because they are more interested in pushing an agenda rather than righting wrongs.

And whom do you believe instead? A single study that can't be replicated because the data is fake.

Yes that's what I'm thinking as well. It's seems likely that inbalanced parasite(of many different kinds) overgrowth is a huge risk factor for lethal covid co-infections. If the immune system isn't already overloaded with parasitic imbalance issues, covid is probably easily dealt with.

Reply on news.ycombinator.com