Toxoplasmosis – A Global Threat (2014) | Hacker News Reader

Toxoplasmosis – A Global Threat (2014)

ncbi.nlm.nih.gov

77 points0x45654 comments

Cats have the evolutionary benefit of being cute to humans. This allows them to be one of the most invasive species in the world.

Case in point is Hawaii; attempts to bring the wild cat populations under control are immediately met with resistance from animal rights groups. This is in spite of the ongoing destruction to wild bird populations. One also has to be extremely careful about washing local vegetables, due to cats spreading toxoplasma.

I think Rattus Rattus might beat them to being the most invasive species in the world

I would think snails are the main reason for washing, but for a different pathogen.

Same story in New Zealand. Even the SPCA here pursues a policy of trap, neuter, release for feral cats despite the overwhelming evidence that they absolutely decimate NZ's native bird populations, which evolved in the absence of such predators.

It's very frustrating, folks can't acknowledge that 'cute and familiar' is causing enourmous ecological harm because it's out of sight, out of mind.

There isn't overwhelming evidence, though. Native bird life in New Zealand has dramatically increased in recent years, despite cats continuing to enjoy relative freedom and huge numbers.

From very low numbers, because they're controlling other predators (stoats)

What do you think the cats are eating?

Whiscas?

Lots of animals eat other animals, we don't kill everything that's not eating a vegetarian diet.

If hypothetically (since I'm not familiar with the data) they're killing some birds but those bird populations remain healthy, is that a problem?

I know of at least three major published studies quantifying the prey caught by domestic cats in New Zealand in Auckland, Christchurch, and Dunedin. All found significant predation of native species by cats, and that it scaled with the population numbers of those species.

On the Dunedin study: >"A year-long study of 208 cats in urban Dunedin showed that they kill more birds, skinks, geckos, and weta than rats and mice."

>"37 Dunedin cats that were known to be prolific hunters, [...] without collars, the cats caught 378 animals, including 82 birds"

>"There is the well-documented case of a lighthouse-keeper’s cat causing the extinction of the Ste-phens Island wren. And near Tongariro National Park, one feral cat was filmed killing 102 short-tailed bats in the Rangataua forest, on the side of Mt Ruapehu, in just seven days in 2010."

https://www.forestandbird.org.nz/sites/default/files/2018-05...

https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1...

https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486....

The success of native breeding, conservation, and re-introduction programmes has been in spite of the country's feral and domestic cats.

This is certainly evidence that cats are killing birds but characterising the numbers in the studies you've cited as absolute decimation seems unfair. I'm genuinely surprised at how low some of these counts are. For example: 37 bell-free cats deemed "prolific killers" only managed to kill 82 birds between them over the course of a year-long study? Even allowing for a large number of unknown kills the impact here seems small.

The lighthouse story is tragic and maddening. While I opted not to adopt a new cat when my last one died, I don't support the predator-free approach to conservation.

>The lighthouse story is tragic and maddening. While I opted not to adopt a new cat when my last one died, I don't support the predator-free approach to conservation.

Why?

Even pet non-feral cats are cute little murder machines. "Oh but not my darling cat." yeah right.

I found this link interesting. The cat tracker images showing where a cat has actually gone in the course of a week are amazing.

https://cattracker.org/tracks/

The Cat Question is an illustrative example of where animal rights and environmentalism diverge.

It's the same same story in Australia. I had multiple vocally Green neighbors in a vocally Green suburb of Melbourne who let their cats have free rein. The mutilated bird carcasses that littered the area were testament to that misguided liberty. Around election time the Greens mailers even included "protecting our pets" as one of its platform items, while at the same time advising voters to rank parties with actual environmental policies, such as the socialists, nearly last.

and, Predator free 2050! (don't mention the deer and pigs)

https://theoatmeal.com/comics/cats_actually_kill

That TheOatmeal comic always comes to mind.

It seems to be very unlikely that brain cysts (that might affect cognition) can form in immunocompetent people — a pathological study of AIDS patients showed cysts in ~20%; background seropositivity in France (where the study was conducted) is ~40%.

Conclusion by the authors: the amount of toxoplasmic agents appeared to be related to the degree of deterioration of the immune status.

> Neuropathological studies in the brains of AIDS patients with opportunistic diseases: https://pubmed.ncbi.nlm.nih.gov/8518200/

The author of this paper, Jaroslav Flegr (https://en.wikipedia.org/wiki/Jaroslav_Flegr), was considered a crackpot for a long time.

There was a profile on him in the Atlantic in 2012 https://www.theatlantic.com/magazine/archive/2012/03/how-you...

Everyone is mentioning cats. 30% of the beef in the US contains toxoplasm gondii. Now, a deep freeze for more than 24 hours will kill it, but how many people eat fresh beef and less than well done? This is part of the reason they recommend pregnant women not eat beef that is cooked less than well done.

This study (https://pubmed.ncbi.nlm.nih.gov/16419752/) failed to find infectious toxoplasma in any retail beef or chicken samples, and only <1% of pork samples (they tested this by feeding cats raw meat).

FDA say about 50% of infections come from contaminated food.

https://www.fda.gov/food/people-risk-foodborne-illness/toxop...

I remember a prior study said about 30% of beef and 24% of venison would test positive, but don't see it now. Also, that's just a positive test number. Transmission numbers could be lower, but likely rise over time with repeated consumption.

They are likely referring to people that interact with cats and then contaminate their own food (fail to wash hands etc.)

That seems extremely unlikely. It says 85% of pregnant women are at risk. Only half as many people own cats. Also, 3 out of the 4 vectors they list on there are food related and do not mention that contact with a cat is required. It mentions raw or undercooked meat several times, and even mentions that is the way that cats acquire it.

I love studies like this. I believe that as science progresses, we're going to see a lot more conclusions like this that previously "benign" things were actually causing problems, or setting the body up for later issues, we just didn't know it.

Toxo is a perfect example. Chicken pocks is another. HPV a third.

Personally I believe "alergies" are actually the result of a viral infection probably from the common cold, that sets off a long term hyper reaction to airborn particles and pathogens. So things like pollen in the air sets off a huge response whereas for some people who never were infected with the virus, they don't get "alergies".

What evidence do you have to back that assertion? Do you speak from a position of expertise?

And the loads of people who have been infected with the common cold, the flu, and other viruses and never develop any allergies? Are you saying you think this only affects a subset of people? Out of curiosity, what lead you to this conclusion?

Personally I've had countless colds and even the flu a few times, and no allergies. In fact, most people I know get a few colds every year and have no allergies. Actually, basically everybody I've ever met has had the common cold at some point. Maybe it's responsible for everything.

Those are great examples!

However, I’m not sure I agree with that allergy hypothesis. The histamine reaction is associated with IgE. This immunoglobulin is associated with parasitic response. A lack of childhood exposure actually higher correlates with higher incidence of allergies and asthma. The theory that has developed from this is that lack of stimulation leads to hyper reaction later when exposed to allergens.

This is all posited by the “hygiene hypothesis”: https://en.m.wikipedia.org/wiki/Hygiene_hypothesis

There is a lot of supporting evidence to go along with it. As well as studies inspecting the impact of gut micro biome.

I suppose this is why I never listened to doctors recommending avoiding peanuts until age 3 or later. It seemed not to make sense. Turns out following that advice created a generation of peanut allergy sufferers!

Many opinions by supposed experts turn out later to be completely wrong. Trusting your own experience is usually wise.

You were a smart two year old!

So why do you trust the studies now? Because they agree with what you think?

Have you looked at the one that's been quoted most often? Because they've very very specific to a population of jewish kids in England and Israel.

Please ignore this "study" and whatever Jaroslav Flegr says. At my university he was mocked for his misuse of statistics - he does it even in this article, giant models with huge sample sizes finding correlations everywhere with p < 0.1.

Also, in this article https://parasitesandvectors.biomedcentral.com/articles/10.11... he says that "pathogen responsible for mood disorders in animals-injured subjects is probably not the protozoon Toxoplasma gondii but another organism; possibly the agent of cat-scratched disease – the bacteria Bartonella henselae." So did he discover yet another behaviour change inducing organism, or is he simply a shitty scientist? Let's have a look: he recruits respondents via Facebook, they take 4 psychological questionnaires (which are usually not very reliable and shouldn't be used in giant correlation tables) and finds effect sizes ranging from eta2 = 0.004 to eta2 = 0.045. Just look at this table - https://parasitesandvectors.biomedcentral.com/articles/10.11... - results are significant because the sample size is 5000, but what are the practical differences? Barely 1 point on a scale that itself has reliability around 0.9 (which is good, but it still leads to standard measurement error greater than Flegr's effect sizes).

Does toxoplasmosis come up in a standard blood panel, or do you have to suspect it and test for it specifically?

There is an antibody test. I believe pregnant women are commonly screened with it.

If there are antibodies for it does that mean your body naturally fights and defeats it, like the cold? Or does it stick around until detected?

You have to test for the antibodies or the DNA. https://labtestsonline.org/tests/toxoplasmosis-testing

(2014)

Definitely still a global threat in 2021, but not the disease that most people have on the brain right now. (Unless they own a cat.)

Which one do they have?

> have on the brain

I see what you did there...

Cats can catch SARS-CoV-2 from humans.

Cats can catch SARS-CoV-2 from cats.

It's reasonable to think we can catch it back (This has happened with minks)

As the human population gets vaccinated it will be interesting to see what happens with cats.

This is remarkably similar to chronic lyme disease.

Why the downvotes? In chronic lyme, the purported issue is lyme hiding out in cysts and causing all sorts of difficult to trace calamity throughout one’s life.

Paper is from 2014, a few years later some scientists realized the answer is ironically, ivermectin.

But good luck getting the NIH/CDC to mention that drug name right now.

Toxo is no joke. Apart from opening the door to other diseases and chronic inflammation, it also induces neurological changes we still barely understand.

It might be a contributor to depression. What we do know is that it correlates positively with motorcycle deaths and risk taking behaviors [1]. Postmortem tests show this. (My old immunology professor used to say that toxoplasma indirectly leads to more organ donation.)

Keep your cats indoors. Or get a dog instead.

Toxo evolved to fuck with mice brains and make them not fear being eaten. Your brain operates on similar biochemistry.

Be careful.

[1] Not a direct citation, but similar claims : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC117239/

I don't get this. Just checked and about 30 percent of women have it when they give birth in Scandinavia - that's a number that keeps rising after that - so lets assume that 50 percent of the population has this at 50.

If this is the case, that's half the population, and if above is true, why isn't "everyone" sounding the alarm?

I have a few family members with cats, so i could pretty well have it.

Doesn't sound like "avoiding" is in any way an option looking at the stats.

Because the toxo doesn’t want us to sound the alarm

Priceless!

Part of why nobody is sounding the alarm is that we just get used to things.

If this month, 2000 extra people die from Y, it's a huge story and everyone jumps on finding a solution.

But if 2000 people have been dying per month from X for decades, no shits are given, it's just part of the background.

In the US it's 3,000 per month for car accidents and 4,000 per month for suicides, by way of example.

> Just checked and about 30 percent of women have it when they give birth in Scandinavia - that's a number that keeps rising after that

You should see the rates in France.

Can we, or can you only reference them sardonically?

The rate in France was 36.7% in 2010 (declining steadily year after year): http://www.bichat-larib.com/revue.presse/revue.presse.resume...

If this disease made your right hand fall off, everyone would be sounding the alarm. It doesn't. It might take someone who is in the bottom quartile for risk taking and move them up to the next quartile. Their behavior would still be within the bounds of normal, their friends might not even notice, but they might become say 50% more likely to die in a motorcycle crash.

The point being we don't really know the consequences, and it's probably a good idea to study this some more.

>but they might become say 50% more likely to die in a motorcycle crash

Or launch a startup.

We didn't have any idea about lead and mental illness, either.

Many historians say it had a role to play in the downfall of Rome.

Reply on news.ycombinator.com