Cats infect humans with a parasite that causes cancer and brain disease

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

Infection of humans with Toxoplasma, a feline parasite that turns mice into zombies, has been linked to an increased likelihood of epilepsy, Alzheimer's and Parkinson's and some types of brain cancer, according to an article in Scientific Reports.

"We assume that the development of these diseases affects many different factors. One of them is the parasite itself and those genes that it activates in the infected brain, protecting itself from the attention of the immune system. Other risk factors can be pregnancy, stress, other infections and bad microflora. If some of these factors coincide, then one of the brain diseases can occur, "says Rima McLeod from the University of Chicago (USA).

Toxoplasma (Toxoplasma gondii) is an intracellular parasite commonly found in the intestines of domestic cats. To date, according to the American CDC, over 60 million people in the United States are infected with it. The widespread prevalence of this pathogen among pets and their owners made scientists pay attention to it.

It turned out that Toxoplasma is able to change the behavior of the host, causing irreversible changes in the brain. It makes mice and chimpanzees fearless at the sight and smell of cats and leopards, and people - prone to suicide and irrational actions, as well as unexplained fits of rage. In addition, in a pregnant woman, Toxoplasma can cause serious defects in the development of the fetus and lead to miscarriage.

Macleod and her colleagues have found that the ingestion of this parasite, which was previously considered relatively harmless, into the human brain can lead to the development of very serious problems. To do this, scientists studied what changes in the functioning of the brain are caused by Toxoplasma gondii, and analyzed how often the possible consequences of these changes are found among healthy and infected people.

In this they were helped by the fact that the University of Chicago for almost forty years followed the lives of about three hundred families, whose members were infected with toxoplasmosis. This allowed scientists to understand how the parasite might influence the development of brain-related health problems.

As these observations have shown, Toxoplasma, penetrating into the brain, changes the work of several dozen genes, suppressing some of them and enhancing the work of other parts of DNA. Almost all of these genes either control the innate immune system, or orchestrate various processes associated with the growth of stem cells and new tissues. The feline parasite suppresses the work of the first group of genes, which helps it to survive, and stimulates the work of the second set, providing itself with food.

Both that and another do not pass without leaving a trace for the infected person, since the weakening of the immune system makes him more prone to the development of cancer and neurodegenerative diseases associated with malfunctioning of the immune system. Excessive changes in other genes can alter how many different signaling molecules the brain produces, resulting in epilepsy, schizophrenia, and other mental disorders.

Most interestingly, scientists have found in the work of human olfactory receptors traces of the same changes that make monkeys and mice not afraid of the smell of cats. How this affects human behavior, biologists do not yet know, but they plan to find out in the course of further experiments with Toxoplasma.

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