While the disease can usually aggravate us, a cunning parasite makes its human carriers more physically desirable, according to a new study.
During experiments, volunteers looked at photos of people infected or not by Toxoplasma gondii, the parasite responsible for toxoplasmosis.
The parasite is spread through exposure to infected cat feces, as well as contaminated food or sex with an infected person.
The study authors found that infected men and women were considered “healthier and more attractive” than those who did not carry the parasite.
It’s likely the intelligent parasite is somehow manipulating our appearance to make us more sexually desirable, which in turn increases its risk of being passed on to other humans, though researchers don’t know. not exactly how.
A pathogenic parasite known to cause psychiatric symptoms such as hallucinations may make infected people more attractive, a study has found. Each image represents the average face of men and women with (left) and without (right) Toxoplasma infection. Since each image was created by merging photos of 10 individuals for each category, the faces shown in the images are not real individuals
Infected men and women were found to be “healthier and more attractive” than those who did not carry the parasite, experts found.
The study was led by Javier Borráz-León, a biologist at the University of Turku in Finland, and published in PeerJ.
“Our results suggest that certain sexually transmitted parasites, such as T. gondii, can produce changes in the appearance and behavior of the human host,” the team states.
‘[This is done] either as a byproduct of infection or as a result of manipulating the parasite to increase its spread to new hosts.
Acute toxoplasmosis in adults has previously been associated with psychiatric symptoms such as delusions and hallucinations.
In mice, toxoplasmosis has also been associated with loss of fear in cats – a clever manipulation of the T. gondii parasite to increase the likelihood of transmission by ingestion by the feline.
Another study showed that male rats infected with T. gondii were preferred as sexual partners by uninfected female rats.
For this new study, the experts compared 35 men and women infected with T. gondii and 178 men and women who did not carry the parasite.
In addition to taking their photos, various measurements were taken to determine their overall health, including body mass index (BMI) and grip strength.
Other data collected included the number of minor ailments, perceived attractiveness and number of sexual partners.
3D rendering of Toxoplasma gondii, a parasitic protozoan that causes the disease toxoplasmosis
Another 205 people were then recruited to assess the attractiveness and perceived health of infected and uninfected people in the photos.
The photos of the participants were also rated by the researchers for fluctuating facial asymmetry – a measure of facial symmetry. High facial symmetry is believed to be an indicator of beauty and good health.
Researchers found that infected men had lower fluctuating facial asymmetry, although no significant differences were found for other health variables.
Infected women, on the other hand, had lower body mass, lower body mass index, a tendency towards lower fluctuating facial asymmetry, greater self-perceived attraction, and a higher number of sexual partners than infected women. uninfected women.
Toxoplasma-infected subjects of both sexes were also found to be more attractive and healthier than uninfected subjects.
Currently, experts can only speculate on how the parasite improves our health and perceived attractiveness.
One theory is that T. gondii infection can produce changes in the facial symmetry of its hosts through changes in the endocrine system – the collection of glands that produce hormones, including testosterone.
Previous studies have shown that men infected with Toxoplasma have higher testosterone levels and women infected with Toxoplasma have lower testosterone levels than uninfected people.
The researchers believe that T. gondii may be specially adapted to ensure that it does not inflict too many “physiological and energetic costs on their hosts”.
The authors say: “If the parasites diminish the attractiveness and health of a host to such an extent that finding a potential mate becomes nearly impossible and survival is severely compromised, the parasites may reduce their own chances of reproducing and to pass to the next generation, especially if the parasites’ pathway includes sexual transmission.’
Further studies with larger sample sizes will need to be conducted to confirm their hypotheses, they add.
“The results lay the groundwork for future research into the manipulation of the human host by sexually transmitted pathogens and parasites,” the team concludes.
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