«Zombie parasite» cats may cause cancer and brain disease in humans

© 2017 AFP / Yasser Al-ZayyatКоты watching a mouse in Kuwait«Zombie parasite» cats may cause cancer and brain disease in humans© 2017 AFP / Yasser Al-Zayyat

Human infection by Toxoplasma, a parasite of cats that turns mice into zombies, was associated with increased likelihood of developing epilepsy, Alzheimer’s and Parkinson’s and certain types of brain cancer, according to a paper published in the journal Scientific Reports.

«We anticipate that the development of these diseases affect a variety of factors. One of them is the parasite genes that it activates in your 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, it may be one of the diseases of the brain,» says Rome Macleod (Rima McLeod) from the University of Chicago (USA).

Toxoplasma gondii (Toxoplasma gondii) is an intracellular parasite, normally found in the intestine of domestic cats. Today, according to the American CDC, more than 60 million people in the US are infected with Toxoplasma. The prevalence of this pathogen among Pets and their owners forced scientists to draw attention to it in recent years.

It turned out that Toxoplasma gondii is able to change the behavior of the host, causing irreversible changes in the brain. They do mice and chimps «fearless» at the sight and smell of cats and leopards, and humans are prone to suicide and irrational behavior, and inexplicable fits of rage. In addition, the penetration of Toxoplasma in pregnant woman’s body can cause serious defects in fetus and lead to miscarriage.

Macleod and her colleagues found that getting Toxoplasma in the human brain, previously considered a relatively harmless parasite can cause very serious problems. To do this, scientists have studied what changes in the brain causing Toxoplasma gondii, and analyzed how often the possible consequences of these changes found among healthy and infected individuals.

In this they were helped by the fact that the University of Chicago for nearly 40 years he followed the life of about three hundred families, whose members have been infected with toxoplasmosis. This allowed scientists to understand how the parasite can affect the development of health problems associated with brain function.

As shown by these observations, Toxoplasma gondii, penetrating the brain, changes the work of several dozen genes, suppressing some and enhancing the work of other DNA segments. Almost all of these genes or control the operation of the innate immune system, or conduct the various processes related to the growth of stem cells and new tissues. Cat parasite suppresses the first group of genes that helps it to survive, and stimulates the second set, providing themselves with food.

Both are not unaffected by an infected person, as the weakening of the immune system makes it more susceptible to the development of cancer and neurodegenerative diseases associated with malfunctions of the immune system. Excessive changes in other genes can change how many different signaling molecules produces the brain, resulting in can develop epilepsy, schizophrenia and other mental disorders.

Most interestingly, scientists found traces of the same changes in the olfactory receptors of humans that make monkeys and mice to fear the smell of cats. How it affects people’s behavior, biologists don’t know yet, but I plan to find out through further experiments with Toxoplasma.


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