Wily toxoplasma parasite hijacks immune cells to travel around the host

I have had to interpret a very complicated study on the Toxoplasma gondii protozoan parasite published on the Cell Host & Microbe website. But it is an interesting study if you take the time to try and interpreted as a lay person i.e., non-scientific person because this parasitic disease is very important in the world of domestic, stray and feral cats.

Toxoplasma parasite engages in 'identity theft' of immune cell to travel around the host's body
Toxoplasma parasite engages in ‘identity theft’ of immune cell to travel around the host’s body. Image: Professor Antonio Barragan, who led the study. Red marks the Toxoplasma parasite. The nucleus is blue, and the cell’s surface is green.
Two useful tags. Click either to see the articles: Toxic to cats | Dangers to cats

It has been written about a lot and the disease is a vehicle for cat haters to denigrate the domestic cat unfairly I would say because even a cat with an active toxoplasmosis infection is only capable of passing it on for 7 to 10 days of her entire life. And, further, most people acquire the disease through eating food contaminated with toxoplasma organisms rather than ingesting infective oocysts in faeces.

Anyway, having got that out of the way, PHYS ORG usefully help interpret this study called: “The Toxoplasma effector GRA28 promotes parasite dissemination by inducing dendritic cell-like migratory properties in infected macrophages”. They say that this wily parasite (my thought) hijacks immune cells enabling the parasite to be undetected, as I understand it, by the immune system. They more specifically hijack a process called ‘chemotaxis’ which describes a system in which immune cells move around the body in relation to chemical agents. They are repelled by some chemicals and attracted by others.

“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 study author.

This parasite hijacks this delicate chemical system and travels around the body. It would seem to be a sophisticated evolutionary development in order to survive and thrive within the host.

Scientists have wondered how the Toxoplasma gondii protozoan manages to infect so many people and animal species (it is zoonotic) and spreads so efficiently in the body.

Arne ten Hoeve, researcher at the Department of Molecular Biosciences, Wenner-Gren Institute at Stockholm University, said: “We have now discovered a protein that the parasite uses to reprogram the immune system”.

The parasite injects a protein into the nucleus of the immune cell and changes its identity. Apparently, it tricks immune cell into thinking it is another type of cell which changes its behaviour. Specifically, it causes infected cells that normally shouldn’t travel in the body to move quickly thereby infecting various organs.

The infected cells become zombies wandering around the body spreading the parasite. Professor Antonio Barragan, who led the study, said that this is why toxoplasmosis is so prevalent in people and cats.

The WHO estimates that at least 30% of the world’s human population carry the parasite. More than 30 million people in the United States carry the Toxoplasma parasite (CDC). The domestic cat is a secondary vector although it is unjustly maligned for the reasons I stated in the opening section of this article.

The disease is normally asymptomatic i.e., there are no symptoms. When symptomatic it affects the lungs, lymphatic system, eyes, spinal cord, brain, and the most common signs are loss of appetite, cough, lethargy and rapid breathing. There may also be evidence of visual and neurological problems. The lymph nodes may enlarge, and kittens may exhibit encephalitis, pneumonia and liver insufficiency.

Veterinarians would say that people should prevent the disease getting into their domestic cats by keeping them inside and preventing them from roaming and hunting.

Cat owners can help prevent infection by wearing disposable plastic gloves when handling the cat’s litter. Faeces should be disposed of carefully so that others don’t come into contact with it. Their litter boxes should be cleaned regularly using boiling water and diluted bleach solution.

Litter trays should not be over cleaned, however, in my view because they need to have the scent of the “owner” of that litter tray on it to encourage defecating in the right place.

Veterinarians would say that cats should not be fed raw meat or allowed to hunt. This is one reason why veterinarians quite strongly object to cat owners preparing their own raw meat diet which is quite popular with some cat owners. It does require skill to prepare a good raw meat diet and there are dangers of cross contamination with bacteria (e.g., Salmonella) and the ever-present toxoplasma gondii protozoan.

I written a lot about this parasite in the past, so I won’t go on. If you wish to read more, could you please click on this link which takes you to many articles on toxoplasmosis. Thank you.

Useful tag. Click to see the articles: Cat behavior

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