Toxoplasma gondii protozoan parasite hijacks immune cells to travel around body

The toxoplasma gondii protozoan parasite hijacks immune cells in order to effectively travel around the body of its host without being attacked by the immune system. In the words of the researcher this is what happens: "This work reveals how an intracellular parasite hijacks chemotaxis in phagocytes and highlights a remarkable migratory plasticity in differentiated cells of the mononuclear phagocyte system".

The author on the PHYS ORG website in referring to the science calls it "identity theft" and they conclude that it is this identity theft which is the secret of this parasite's success. Toxoplasma gondii is in a lot of people and a lot of cats. It is zoonotic. That means it can be transferred from animals to people.

An immune cell that has been infected by Toxoplasma parasites (red). Photo: Professor Antonio Barragan.

The parasite injects the protein into the nucleus of the immune cell. This changes the cell's identity, which tricks other cells into no longer recognising the immune cell as an immune cell. It changes the behaviour of the immune cell allowing it to travel around the body.

In the opening paragraph I've used the word 'chemotaxis'. This word describes a phenomenon in which the direction of a cell's locomotion determined by an extracellular gradient of chemicals. It is the migration of cells towards attracting chemicals and away from repellents.

The toxoplasma gondii protozoan hijacks this process which allows it to travel around the body. It is another way of describing the process of survival of this successful parasite. 

A lot has been written about toxoplasma gondii. A lot of people who hate cats write about it and say that it causes schizophrenia in people because the protozoan migrates to the brain of people and alters their mental processes. They say those things to denigrate the domestic cat.

I don't think that there is hard science to support that statement. Briefly, cats are a secondary vector for this parasite, and they are likely to acquire the infection by consuming infected birds or rodents and sometimes but rarely ingesting oocysts from contaminated soil.

People can get the disease from eating raw or undercooked pork, beef, mutton or veal or unpasteurised dairy products that contained toxoplasma organisms. They can also get the disease by mishandling domestic cat faeces in which there are oocysts. Infective oocysts are only passed for a very short time, however.

The disease is normally asymptomatic i.e., without symptoms. The most common signs of toxoplasmosis in domestic cats are loss of appetite, lethargy, cough and rapid breathing. There may be neurological signs. The lymph nodes may enlarge. Kittens may exhibit and encephalitis, liver insufficiency or pneumonia.

RELATED: Health tip: preventing a toxoplasmosis infection from cat faeces.

Prenatal infection may be responsible for abortion and stillbirth. Many cats show clinical signs that are concurrent with feline immunodeficiency virus or feline leukaemia virus.

People are frightened of this virus because it is zoonotic, as mentioned. It's important to understand the mode of transmission from cats "to understand how minimal the risk is" (Cat Owner's Home Veterinary Handbook).

Even a cat with an active toxoplasmosis infection is only capable of passing it on for 7 to 10 days of her entire life when there is an acute infection.

The experts will say that there is no need for pregnant women to get rid of their domestic cat companion. They can take precautions to avoid contact with faecal material from cats by for example wearing gloves when gardening and cleaning the litter box.

I have written many pages on this disease which you can access by clicking on this link.

Elon Musk tweets that toxoplasmosis forces humans to create superhuman artificial intelligence

Elon Musk has suggested in a tweet on Twitter that the protozoan parasite toxoplasmosis, of which the domestic cat is the primary vector, is forcing humans to create superhuman artificial intelligence. That is the interpretation by the author of an article on The_Byte website.

Photo by Steve Jurvetson on Wikipedia. 

Screenshot of the tweet. The originals sometimes go wrong a leave a link, no more.

I think he might have been a little bit stoned when he wrote this tweet because the underlined words (underlined by me) he has used don't make any sense at all to me. They are as follows:

Toxoplasmosis infects rats, then cats, then humans who make cat videos. AI trains achieves superhuman intelligence training on Internet cat videos, thus making toxoplasmosis the true arbiter of our destiny.

That has been interpreted as meaning that toxoplasmosis makes people create AI. I don't get it and I'm not sure the interpretation is correct because it's very unclear but I thought I'd pass it on.

The interesting aspects of his tweet is that the National Geographic tweeted that hyenas become more reckless when they've got toxoplasmosis which makes them more vulnerable to being killed by lions. And mice become more reckless when they contract toxoplasmosis which makes them more vulnerable to being eaten by cats. And then cats get toxoplasmosis from the mice. And then they shit toxoplasmosis oocysts and the cycle continues. The point that should be made, though, is that cats only pass toxoplasma gondii oocysts for a very short period of time. This point is often forgotten.

And indoor cats that are highly unlikely to get toxoplasmosis. Back to Elon Musk. I think he is a great guy but under an enormous amount of stress which is self-imposed. He probably goes home of an evening and has a few drinks to chill out (and more?!) and then heads for Twitter in a slight haze and taps out the words we see on this page. What do you make of it?

Australian scientist claims that diseases transmitted by cats to people cost the Australian economy AU$6 billion annually

I find this extraordinary. Unfortunately I don't have access to the full article by Donna Lu on the newscientist.com website because you have to subscribe to the site and I don't want to do that (but see update below please). But the opening paragraphs state that diseases transmitted by the domestic cat to people, including cat scratch disease, cost the Australian economy more than AU$6 billion per year (4.2 US dollars). The costings are based upon the impact on human health and livestock production. Clearly they are inferring that domestic cat spread disease to livestock as well or is it that people are incapacitated and therefore can't farm? They may be referring to toxoplasmosis. No doubt they are because this disease always comes up in these sorts of discussions. The author emphasises cat scratch disease and bites.

Prof Sarah Legge. Photo: Australian National University.

Well, there you are. I will have to speculate as to how they have calculated this cost. But they must be saying is that cat owners and non-cat owners are being bitten or scratched by domestic and stray cats which removes them from the workplace for a day or two while they recover. Or perhaps they go to hospital but this is normally extremely rare.

99% of cat bites and scratches do pretty well nothing in terms of interfering with one's day-to-day living. That's my personal experience. Toxoplasmosis is almost always asymptomatic in people i.e. no symptoms. Cat scratch disease is rare in people. Certainly, cats can cause it but I would speculate that one in 500 or 1000 scratches results in cat scratch disease. It needs to be treated. Bites are not uncommon but most often are irritations more than injuries that need to be dealt with immediately. That said when bitten by a cat you have to be vigilant and watch the area where you were bitten. As soon as it looks as if it's becoming infected you must take antibiotics as prescribed by a doctor to ensure that they are the right antibiotics. This is an absolute must as stated. Because if you let an infection caused by a cat bite get worse it can cause a serious injury and it can lead to hospitalisation.

Zoonotic diseases transmitted by cats to people are on the whole pretty rare and therefore have difficulty in understanding how they arrive at a AU$6 billion cost.

Update

I have found an article on a Chinese website which discusses the research by Prof Sarah Legge of the Australian National University and the University of Queensland. She argues that annually over 500 people die in Australia and there are 11,000 hospitalisations due do diseases transmitted by cats to people. The costs include medical treatment, reasonable relevant expenses, lost income et cetera.

She refers to toxoplasmosis as mentioned, roundworm and cat scratch disease. Of these toxoplasmosis has the biggest negative impact on the Australian economy. She claims that it has possible long-term effects on behaviour and mental health. Note, the word "possible". She doesn't know and therefore how can she make calculations on the back of it.

She claims that the parasite that causes toxoplasmosis causes 200 deaths and 6,500 hospitalisations due to car accidents which could be avoided in Australia annually. She believes that the disease causes mental health disorders which I presume are translated into poor driving! She claims that one in five cases of schizophrenia and one in 10 cases of suicide were caused by toxoplasmosis. She wants domestic cats to be kept indoors all the time in Australia and for people to wash their hands thoroughly after handling cat litter or gardening. This is to stop transmission of toxoplasma gondii oocysts in the soil or faeces in the litter tray to the hands and from the hands to the mouth and therefore ingested.

She also claims that feral cats around towns are a reservoir for disease.

Human behavior

We have to discuss human behaviour in this equation. Most cases of toxoplasmosis are caused by mishandling of raw foods in the kitchen. That's due to careless human behaviour. Being scratched or bitten by cat is often put down to careless human behaviour. Contracting toxoplasmosis through mishandling of cat litter or when gardening, once again, can be put down at least in part two careless human behaviour. Therefore this vast economic loss to the economy in Australia as stated is in large part due to human behaviour. It is unreasonable to blame the cat exclusively as this professor is.