Parasite

Parasites can make you more attractive

Parasites may have evolved countermeasures to manipulate the appearance of their host in order to avoid such a problem.

PAZH | Imagine that a parasite has infected you and that parasite needs to have sex in order to move to a new host. It would certainly be in that parasite’s interest to help you become more physically attractive to a mate and act more clearly.

An extraordinary new study suggests that the landscape may actually be at play with one of the most common parasites in the world, Toxoplasma gondii (T. gondii), which potentially makes the appearance of its human host more sexually active. Manipulates to make it attractive.

Javier Borraz-Lyon of the University of Turku has long wondered how parasites have been found to influence host behavior as they move into a new host. T. gondii in particular has been subject to a great deal of prior study, researchers finding parasites can, for example, attract an animal host to the smell of urine from predatory cats. This induces the host to take risky behavior, increasing the likelihood of it being eaten by a predatory cat, thus providing a way for the parasite to reach its optimal host.

“…It is well known that Toxoplasma gondii needs to reach its definitive host (usually a domestic cat or other member of the Felidae family) for sexual reproduction,” Borraz-Lyon explained to New Atlas. “And an effective way to do this would be to manipulate the host’s behavior such that it has been described for the ‘fatal attraction phenomenon’ in which Toxoplasma infection inhibits the mice’s innate aversion to cat urine, allowing the cat to become infected.” rat (similar results have also been observed for infected chimpanzees, hyenas and humans).

And as parasites can influence host behavior for further transmission, animals avoid mating with other animals that seem sick. One researcher dubbed this the “infection indicator hypothesis”, suggesting that females would naturally avoid mating with parasite-infected males as a way of protecting their future offspring from becoming infected.

So some parasites may have evolved countermeasures to manipulate the appearance of their host in order to avoid such a problem. This can be as simple as being able to live asymptomatically in its host, avoiding causing any of the major visible features of a parasitic infection. But a compelling 2011 study took the hypothesis a step further, suggesting that T. gondii infection in male rats actually increased their attraction to female rats.

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, [it’s] It is plausible to think that Toxoplasma gondii may undergo some phenotypic change to increase the attractiveness of its host, which, at the same time, would increase transmission-related benefits for the parasite,” Boraz-Lyon said. “In fact, it has been observed that male mice that have been experimentally infected with Toxoplasma gondii have some changes in their testosterone levels, and are more sexually attractive and preferred as sexual partners by non-infected females. results, which supports our evolutionary interpretation.

So Borraj-Lyon was left with a major question: if this parasite is manipulating physical characteristics and behaviors in rodent hosts to help it complete its life-cycle, will it do the same things in human hosts? Can do?

At first glance the hypothesis is beautiful. But Borraz-Lyon points to a fair body of evidence that suggests that T. gondii infection in humans affects a number of symptoms. Several studies have found that T. gondii infection in men is related to higher testosterone levels than in non-infected men.

A more recent study found that people infected with T. gondii were more likely to engage in risky entrepreneurial behavior. It seemed that those harboring the parasite had less “fear of failure” in relation to bold new business ventures. Of course it is clearly not beneficial for a parasite to help humans in its economic ventures, the idea that the parasite is doing something for its host that affects the host less than risky behavior, even more so. Sexual behavior may occur. And it certainly could be helpful for a parasite that has recently been suspected of being able to move to new human hosts through sexual activity.

The first phase of the new study examined a variety of physical and behavioral differences between infected and uninfected people. This included self-reported measures of attractiveness, number of sexual partners, facial symmetry and body mass index.

“In the first phase of the study, we found that Toxoplasma-infected men had greater facial symmetry than non-infected people, while Toxoplasma-infected women had lower body mass index and lower body mass,” Borraz-Lyon said. “Toxoplasma-infected women also had higher facial symmetry, higher self-perceptions of attractiveness, and a higher number of previous sexual partners than non-infected people.”

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One of the big surprises for Borraz-Lyon was the finding of greater parasite-related phenotype differences in females than in males. This was unexpected, as most prior research into the effects of T. gondii infection found greater hormonal and behavioral differences in males.

In the second part of the study, nearly 200 subjects were recruited to view a group of photographs of infected or uninfected people and to evaluate their perceived attractiveness and health. Regardless of sex, participants with T. gondii infection were consistently rated as more attractive than healthy and uninfected subjects.

The above is a composite image that blends 10 different images together to preserve the anonymity of the study participants. (A) Images on the left are of males and females infected with T. gondii and (B) images are of uninfected participants.

Borraz-Leon et al.

Of course, if you’ve read this far, you may have a lot of questions running through your mind, such as how can a parasite actually make a person more attractive? The “how” question in particular is a challenging one for Borraz-Lyon, as research on the ways parasites manipulate their host’s physiology is very limited.

“… Experimental evidence in rodents has shown that these effects may be mediated by brain neurotransmitters and sex and stress hormones and their effects on the brain,” Borraz-Lyon said. “For example, it has been shown that Toxoplasma gondii can directly increase brain serotoninergic and dopaminergic activity in its hosts through alterations in gene expression. In addition, there is evidence that this parasite activates RNA expression of the luteinizing hormone receptor. Thus, it is possible to suggest that the behavioral and physiological changes observed in Toxoplasma-infected subjects, including humans, are due to the effect of this parasite on brain architecture as well as neurotransmitters. and may be linked to the synthesis and regulation of steroid hormones.”

This is all heavy speculation right now, but beyond any explanation as to how these parasites might be changing the way we see, it is an even bigger question of what makes us so fundamentally attractive to a mate. Physical attractiveness in humans is largely influenced by cultural factors, so from one point of view it seems insane to consider the possibility of a parasite being able to change the physical characteristics of a human host.

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Again, Borraz-Lyon is fascinated by this question, and what the implications of his research could be. Is this parasite based on some “universal” characteristics of human attraction?

“This is a very good question!” Boraz-Leon replied. “Although mate preferences may fluctuate according to variation in socio-ecological conditions, there is evidence that some phenotypic traits are ‘universally’ attractive, which is the case for facial symmetry, which is actually the case in Toxoplasma-infected subjects.” Furthermore, the fact that the Toxoplasma-infected subjects in our study were rated as more attractive and healthier by subjects from different countries (ie, Finland, England, France and Mexico), suggest Giving supports the hypothesis that some of the changes caused by this parasite may be seen as ‘universal’ attractive.”

The findings of this new study are just the beginning for Borraz-Lyon. He is already planning a number of new at-home tests on the specific physiological features of T. gondii infection. How can it affect neurotransmitters and hormones? And can the parasite really change human sexual behavior?

It is estimated that half of the world’s population is infected with T. gondii. So chances are someone reading this article right now unintentionally harbors the parasite and it may be affecting your behavior in subtle ways that you may never even notice. Can a parasite make you more attractive to others? Maybe this is driving you to take a little riskier behavior. Or there is always the chance that all those things are you.

The new research was published in the journal PeerJ.

Source | Newatlas

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