The parasite that causes toxoplasmosis controls the mind and causes psychological disturbances and suicides

I have read a lot of shocking news throughout my life, however much like the one I read the other day in National Geographic magazine. The article referred to a parasite called “Toxoplasma Gondii”, which causes toxoplasmosis.

Czech-born evolutionary biologist Jaroslav Flegr has done a lot of research to find out more about how this protozoan affects humans. This researcher concluded that toxoplasma gondii can control our brains, increase suicides and cause mental disorders like schizophrenia or bipolar disorder.

Toxoplasma gondii: the intelligent parasite

The cause of toxoplasmosis is one of the most interesting parasites on the planet and can affect all warm-blooded animals, including humans. In addition, birds and insects (flies, cockroaches) can carry the parasite and spread it widely. Cats are the only animals where the parasite produces eggs, which is why they are known as definitive hosts; other animals are called intermediate hosts because the parasite does not produce eggs.

Cats are usually infected when they eat uncooked and infected meat, such as prey hunted in their habitat.. In order for the parasite to follow its life cycle and become an adult parasite, it must become lodged in the intestines of cats. Therefore, the way to achieve this is to be ingested. And how is this possible? Studies suggest that the parasite has evolved to be able to ‘hack’ neural circuits to change rodent behavior with such precision, that cats lose their fear (and even get excited about their smell) so that they are easy prey for cats. We all know that mice and rats are cats’ favorite prey.

Toxoplasmosis in humans

Now, and in humans … what exactly is going on? Blood tests show that with toxoplasmosis, in 40% and 60% of cases the parasite entered the body of these people and produced the formation of antibodies. But how do people get infected? So in different ways:

  • Eat raw or undercooked meat.
  • Handle raw meat without gloves.
  • Ingest raw goat’s milk.
  • Eat contaminated and improperly washed fresh vegetables.
  • During gardening or in children’s play areas, if the sands are contaminated.
  • Drinking water contaminated with sporulated oocysts.
  • Infection does not occur by touching or stroking the cat, but by touching the ground where the cats have deposited their droppings, because after 24 hours after the deposit there is a risk of infection (provided they put then their hands in their mouths without cleaning them).

However, very few people show symptoms of the diseaseAs with a normal immune system, anyone can turn off the parasite or just show feverish symptoms or inflammation of the lymph nodes. Although experts claim that the major problem occurs during pregnancy. The highest risk occurs when the infection is acquired during the first months of pregnancy, with abortions and fetal malformations.

Toxoplasmosis causes behavioral changes in humans

Although it appears that the parasite does not cause visible symptoms in most cases, there is research that does not claim the same. As already mentioned, one of the first scientists to take an interest in toxoplasmosis and its effects on humans was Jaroslav Flegr, and found that changes in behavior that cause toxoplasmosis in rodents, such as changes in reaction times, lethargy, or decreased fear, also appear in infected humans.

In addition, Swedish scientists recently discovered that in order to travel throughout the body and reach the brain, toxoplasma gondii sequesters the same cells that are responsible for expelling foreign bodies, white blood cells. Apparently, white blood cells produce a neurotransmitter that is responsible for reducing fear and anxiety in rodents and humans.

Flegr himself, moreover, after analyzing the database of different hospitals, found that an infected person is more than twice as likely to have a car accident. According to Flegr, it has to do with reducing reaction time.

The relationship between toxoplasmosis and mental disorders

In 2003, Fuller Torrey, a researcher at the Stanley Medical Research Institute in Bethesda, USA, observed a relationship between schizophrenia and toxoplasma gondii. Specifically, women with high levels of the parasite were more likely to give birth to babies at risk of developing schizophrenia.

The hypothesis suggests that while for most infected people toxoplasma has minor effects, for others the changes are much more exaggerated. This idea gained strength with subsequent studies, as another study found that antipsychotics worked just as well as other drugs used to treat this condition, thus indicating there is a relationship between psychological disorders and Toxoplasma gondii infection.

One of the causes of the relationship between toxoplasmosis and schizophrenia was explained by a group of scientists in the UK, who discovered in 2009 that the parasite had two genes for making L-DOPA, the precursor molecule dopamine. High levels of this neurotransmitter are associated with schizophrenia

Another study by American scientists found that among 7,440 mental health patients, there was a significant relationship between toxoplasma infection and a type of bipolar disorder in which patients suffer from a greater predominance of depressive symptoms. .

Toxoplasmosis and suicide

Studies on the relationship between toxoplasmosis and psychological problems have continued and have yielded surprising results. A study published in 2009 by the Journal of Nervous and Mental Disease states that there is a link between suicide and infection with this parasite. But, of course, this has happened in people who already have mental illness. Likewise, another study found that countries with high rates of toxoplasmosis infection also had high suicide rates.

In Denmark, a relationship has also been found between suicide and toxoplasmosis. A joint survey between the Danish National Hospital Register and the Danish Central Register of Psychiatric Research found that women infected with toxoplasma were 54% more likely to attempt suicide and were twice as likely to kill themselves.

In fact, these women were more likely to attempt violent suicides. But what is even more concerning is that the risk of attempting suicide was positively correlated with the level of infection. Women with the highest levels of antibodies were 91% more likely to attempt suicide than uninfected women. The link between the parasite and suicide was maintained even for women who had no history of mental illness.

Bibliographical references:

  • Arling TA1, Yolken RH, Lapidus M, Langenberg P, Dickerson FB, Zimmerman SA, Balis T, Cabassa JA, Scrandis DA, Tonelli LH, Postolache TT. (2009). Toxoplasma gondii antibody titers and history of suicide attempts in patients with recurrent mood disturbances. Journal of Mental Illness; 197 (12): 905-8. doi: 10.1097 / NMD.0b013e3181c29a23.
  • Flegr, J. (2013) Influence of latent Toxoplasma infection on human personality, physiology and morphology: advantages and disadvantages of the Toxoplasma-human model in the study of the manipulation hypothesis. Journal of Experimental Biology 216: 127-133; doi: 10.1242 / jeb.073635.
  • Flegr, J. (2007) Effects of Toxoplasma on Human Behavior. Schizophrenia Bulletin 33 (3): 757-760. doi: 10.1093 / schbul / sbl074
  • National Geograpfic: “Toxoplasmosis, new discoveries”.

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