The parasite can persist for a long time in the body and it is suspected that it can lead to personality changes in humans. The case of the kamikaze mice and the choice of unscrupulous behavior
Toxoplasmosis, a very common disease (caused by a parasite, Toxoplasma gonadii, is it really asymptomatic? We know that the disease is particularly dangerous for pregnant women due to the risks it can have on the fetus because it can cause miscarriages or mental development problems in babies. However for the rest of the population the disease is almost always asymptomaticeven if the parasite it can remain silent in the body and in the people’s brains for many years.
How widespread is the infection
Il toxoplasma gonadii a very common parasite, which generally reproduces in cats and which is transmitted to humans through the raw or undercooked meatfburp and unwashed vegetables and coming from contaminated soils and by handling cat litter. It is estimated that the parasite infectsmore than a third of the world’s population. In Italy, about 60% of the population contracts toxoplasma during their lifetime: the acute infection is asymptomatic in 90% of cases, while the remaining 10% develop only mild retrocervical adenopathies.
The influence on human behavior
The parasite reproduces in the intestines of felines (the definitive hosts), but has a rather complex life cycle and spends a period of time hosted by many other animals: from birds to crocodiles, from rodents to cetaceans up to humans. When Toxoplasma gonadii enters the body of intermediate hosts, it reproduces asexually, persisting in the organism with cysts in different tissues, with greater preferences in the brain. When the immune response is deficient (for example fetuses or immunosuppressed subjects) the toxoplasma is not “encysted” but proliferates in the intermediate host, causing severe disease. When, on the other hand, the immune system works well, the cyst formation process is asymptomatic or causes only some slight discomfort. At least, apparently. Until recently, the presence of toxoplasma cysts in humans was in fact considered asymptomatic. However, there is a growing body of evidence to prove otherwise: the infection could in fact affect human behavior making it less cautious.
I topi kamikaze
Many behavioral biology studies have been done in animals. It has been seen that when a rodent hosts toxoplasma it begins to manifest reckless behaviorsfor example, it frequents places well marked by the smell of cat urine and faeces (so much so as to earn the appellation of topi kamikaze), while rodents without toxoplasma appear decidedly more cautious and move away from places where they encounter signs of the presence of cats precisely to minimize the possibility of being eaten by predators. Equally disinhibited behaviors have also been observed in other animals harboring toxoplasma. Hyenas approach lions; Tasmanian masupials appear careless and are run over more often on the roads; sea otters (infected by cat feces contamination of the water) end up being more often prey for sharks. L’abandonment of prudent behavior implies a radical change in one of the main characteristics of animal life: linstinct for self-preservation. so is it possible that a tiny parasite makes decisions for the animal?
What do we know about man
Given the premises, what happens in humans? Can Toxoplasma Affect Human Behavior? The first studies describing the potential associations between latent Toxoplasma gonadii infection and human neuropsychiatric disorders date back to the 1950s. More recently, meta-analyses have been conducted investigating the association between the presence of the parasite and a wide variety of cognitive and neuropsychiatric disorders including the Alzheimer’s disease, epilepsy, bipolar disorder, obsessive compulsive disorder. Data so far support that approximately 20% of cases of schizophrenia related to the presence of toxoplasma cysts.
It has been observed that the presence of toxoplasma cysts among people who die in road accidents disproportionately high enough to raise suspicions that the parasite may play a role in the less cautious behavior of drivers. A 2018 study of nearly 100 deaths linked the presence of parasite DNA to risky behaviors such asexcessive alcohol consumption.
The parasite might generate it too personality changes. Research by the University of Prague about ten years ago concluded that people with toxoplasma had more unscrupulous and contemptuous of danger compared to participants who had not had contact with the parasite. The degree of conscientiousness seemed to decrease with increasing duration of infection suggesting that these differences are due to slow changes of a latent toxoplasmosis, and not to an acute transient infection. Furthermore, this result supported the theory that the changes in personality are due to the parasite and not vice versa that risk-taking people are more prone to infection. According to a Danish study involving 16,000 women, those who lived with toxoplasma were more enterprising, especially in starting their own business, but they also abandoned their business more easily. Other research shows that people infected with toxoplasma are less inclined to understand the benefits that their actions could achieve by making them more exposed to risks, ignoring the consequences.
A link to brain tumor risk
The parasite could even have even more insidious effects on our health. Recent research published in the International Journal of Cancer suggests a link between Toxoplasma gondii and the chances of developing a brain tumor. for now only a hypothesis to be investigated because the risk appears low and the scientists are still looking for a direct cause-effect relationship, but in their conclusions the American scholars report that although investigations on larger numbers of people are certainly needed to have confirmations, the Current findings indicate that people most exposed to Toxoplasma gondii are more likely to have brain glioma.
January 25, 2023 (change January 25, 2023 | 2:43 pm)
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