The parasite that causes Toxoplasmosis controls the mind and causes psychological disorders and suicides

March 23, 2024

I have read many shocking news throughout my life, but few like the one I read the other day in the magazine National Geographic . The article referred to a parasite called "Toxoplasma Gondii", which causes Toxoplasmosis.

An evolutionary biologist of Czech origin, Jaroslav Flegr, has done a lot of research to know more about how this protozoan affects human beings. This researcher has concluded that toxoplasma gondii can control our brains, increase suicide and cause mental disorders such as 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 be carriers of the parasite and expand it widely. Cats are the only animals where the parasite produces eggs, which is why they are known as definitive hosts; in the rest of the animals they are called intermediate hosts because the parasite does not produce eggs.

Cats usually become infected when they eat undercooked and infected meats, for example, prey hunted in their habitat . In order for the parasite to follow its life cycle and become an adult parasite it must be lodged in the intestines of the felines. Therefore, the way to achieve it is to be ingested. And how do you get this? Studies suggest that the parasite has evolved so that it is able to "hack" neural circuits to change the behavior of rodents with such precision, that they make them lose their fear of cats (and even become excited by their smell). to make them easy prey for cats. We all know that mice and rats are the favorite prey of cats.

Toxoplasmosis in humans

Now, and in humans ... what exactly happens? Blood tests show that toxoplasmosis, in 40% and 60% of cases the parasite has entered the body of these people and producing the formation of antibodies. But how do people get infected? Well in different ways:

Eating undercooked or raw meat.
Manipulating raw meat without gloves.
Ingesting raw goat milk.
Eating fresh vegetables contaminated and not washed properly.
During gardening or playgrounds for children, if the sands are contaminated.
Drinking water contaminated with sporulated oocysts.
The infection does not occur touching or caressing the cat, but touching land where the cats have deposited their feces, because after 24 hours after the deposition there is a risk of infection (as long as they then put their hands in the mouth without cleaning them) .

But nevertheless, very few individuals have symptoms of the disease , because with a normal immune system anyone can counteract the parasite or simply have febrile symptoms or inflammation of the lymph nodes. Although experts say that the important problem occurs during pregnancy. The greatest risk arises when the infection is contracted during the first months of pregnancy, presenting abortions and fetal malformations.

Toxoplasmosis causes behavioral changes in humans

Although it seems that the parasite does not cause visible symptoms in most cases, there are investigations that do not affirm the same. Jaroslav Flegr, one of the first scientists to be interested in toxoplasmosis and its effects in humans, found that changes in the behavior that toxoplasmosis causes in rodents, such as changes in reaction times, lethargy, or decreased fear, also appear in infected humans .

In addition, Swedish scientists recently discovered that 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, the white blood cells produce a neurotransmitter that is responsible for reducing fear and anxiety in both rodents and humans.

Flegr himself, after analyzing the database of different hospitals, discovered that an infected individual is more than twice as likely to suffer a car accident. According to Flegr, this has to do with the reduction of the reaction time.

The relationship between toxoplasmosis and mental disorders

In 2003, Fuller Torrey, a researcher at the Stanley Medical Research Institute in Bethesda (United States), observed a relationship between schizophrenia and toxoplasma gondii . Specifically, that women with high levels of the parasite were more likely to give birth to babies who could develop schizophrenia.

The hypothesis suggests that, while for most people who are infected, toxoplasma has minor effects, for others, the changes are much more exaggerated. This idea has gained strength with subsequent studies, because other work has found that antipsychotics worked just as well as other medications used to treat this pathology, affirming, in this way, that There is a relationship between psychological disorders and toxoplasma gondii infection .

One of the causes of the relationship between toxoplasmosis and schizophrenia has been explained by a group of scientists in the United Kingdom, who in 2009 found that the parasite has two genes for the manufacture of L-DOPA, the precursor molecule of dopamine. . High levels of this neurotransmitter are associated with schizophrenia

Another study by US 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 a greater prevalence 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 affirms that there is a link between suicide and infection by this parasite. But, of course, this happened in people who already have a mental illness. Similarly, another study found that countries with high rates of toxoplasmosis infection also had high suicide rates

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

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

Bibliographic 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 disorders. Journal of Nervous Mental Disease; 197 (12): 905-8. doi: 10.1097 / NMD.0b013e3181c29a23.
Flegr, J. (2013) Influence of latent Toxoplasma infection on human personality, physiology and morphology: pros and cons of the Toxoplasma-human model in studying 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".