Toxoplasma gondii, a brain-hijacking parasite, appears to be almost everywhere. It''s estimated that it would infect up to 50% of people, and it may alter human behavior, outcompared to that of many other animals.
A parasite has been linked to a wide spectrum of neurological diseases, including schizophrenia and psychotic episodes, and experts continue to uncover more devastating effects.
Researchers from a research found that individuals and women infected with the parasite ended up being rated as more attractive and healthier-looking than non-infected individuals.
On the face of it, it might sound odd and unpredictable. But, hypothetically speaking, the phenomenon might make sense from an evolutionary biology perspective.
Above are composite images of ten Toxoplasma-infected women and men (a) and 10 composite images of ten non-infected women and men (b).
Researchers believe that in the midst of the countless neurobiological changes T. gondii is likely to affect its hosts, some of the effects may occasionally benefit infected animals, which might then benefit the parasite, by sustaining its own transmission prospects.
"In one study, Toxoplasma-infected male rats were perceived as more sexually attractive, and by non-infected females, according to the study. In a new paper led by Javier Borraz-Leon, the first author and biologist from the University of Turku in Finland,
A lot of research has been done to investigate whether similar effects can be found in human cases of T. gondii infection.
The evidence is far from clear, but some evidence suggests that infected men have higher levels of testosterone than non-infected men.
Men with higher testosterone levels might be more likely to enter the parasite in the first place, with higher risk-taking behaviors.
The parasite may be able to subtly alter its host phenotype, manipulating chemicals in the animal''s body, as well as neurotransmitters and hormones, for its own later problems.
Borraz-Leon and his team suggest that these modifications would be significant.
"Some sexually transmitted parasites, such as T. gondii, may alter the appearance and behavior of the human host, either as a result of the infection or as a result of the manipulation of the parasite to expand its spread to new hosts," according to researchers.
The researchers calculated a comparison of 35 people (22 men, 13 women) who were not treated with T. gondii, including 178 people (86 men, 92 women) who did not carry the parasite.
All participants (including those infected) were non-familiar college students who had previously had their blood tested for another examination. T. gondii:
Following a series of different experiments involving participants, including surveys, physical measurements, and visual assessments, the researchers found Toxoplasma-infected subjects had significantly lower facial fluctuating asymmetry than the non-infected people.
Usually, low levels of asymmetry are linked to better physical health, good genes, and attractiveness, among other things.
Women carrying the parasite were found to have less body mass and decreased BMI than non-infected women, indicating both higher self-perceived attractiveness and a greater number of sexual partners.
Using a group of 205 independent volunteers, photographs of participants'' faces were assessed, and the participants remained significantly healthier than non-infected participants.
Researchers predict that a T. gondii infection might alter the facial symmetry of its hosts if it occurs due to changes in endocrinological variables, such as testosterone levels.
A parasite might also infiltrate host metabolic rate, removing infected people in ways that might impede their health and attractiveness perceptions.
All of this is at this point, and the team recognizes that other interpretations are also viable, including the notion that highly symmetrical, attractive individuals may somehow better afford the physiological costs associated with parasitism, which in other ways are considered a health problem.
Considering whether or not the interpretation is correct, it''s impossible to say for sure based on this one study alone, and the researchers recognize that the small sample size of their experiment is a limiting factor for its statistical analysis.
Future studies with a greater number of participants will be required to validate or denied their overall belief.
Perhaps, maybe, they argue that this frightening parasite isn''t necessarily our adversary.
"It is possible that the apparently non-pathological and potentially beneficial interactions between T. gondii and some of its intermediate hosts, such as rats and humans, are the result of co-evolutionary measures that can, or at least do not, affect both the parasite and the host,," says one researcher.