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.