T. gondii: The hot people's parasite

20 to 30 per cent of us are already infected with the parasite which, in addition to being linked to attractive physical traits in humans, may also make you weirdly attracted to the smell of cats.

Emma Jones 4 minute read May 25, 2022
gray tabby cat lays on the neck of a young man. close up

Toxoplasma gondii (T. gondii) is a fairly common parasite that can only reproduce in the digestive tract of cats. GETTY

People infected with this fairly common parasite were ranked as more attractive and healthier than the non-infected, according to research published in the journal PeerJ.

Toxoplasma gondii (T. gondii) is a fairly common parasite that nestles in the skeletal muscle, myocardium, brain or eyes of warm-blooded animals. It can only reproduce in the digestive tract of cats and is spread to other animals (including humans) when they consume food or water contaminated with cat feces — or eat undercooked meat already infected with the parasite.

This parasite is also very good at catching a ride: it is estimated that one-third of the global population is already infected. (We’ll wait while you take a shower before reading the rest of the article.)

The good: People infected with the T. gondii parasite could be hotter?

While it seems random, there may be an evolutionary benefit to the parasite improving certain aspects of its host’s life. Parasites need their host (or victim) to thrive. If the victim becomes sickly or dies before the parasite can reproduce, it would also negatively impact the parasite’s survival. If a host is also able to thrive and reproduce, it would funnel more resources to the parasite and give it more opportunities to spread to another host.

Researchers took data from 213 healthy college students who had previously been tested for Toxoplasma IgG, where 35 participants had tested positive. They then had the participants fill out questionnaires regarding age, height, body mass, marital status and the number of sexual partners and the number of minor ailments in the last year. Researchers also took photos of each participant and analyzed them for facial asymmetry.

Facial analysis indicates that the infected male participants had significantly lower facial asymmetry than the non-infected male participants (symmetrical faces are seen as more pleasing.) While toxoplasma-infected women tended to have lower facial asymmetry, this finding wasn’t as significant as for the men. Infected women, the researchers note, did had lower body mass than non-infected women.

A separate group of 205 participants were also asked to rate photos of different people, with the photos containing images of both non-infected and Toxoplasma-infected subjects. The infected subjects (both men and women) were rated to be significantly more attractive and healthy than non-infected individuals.

The researchers also point to several past studies that have found males infected with T. gondii tend to have higher testosterone levels, which correlates with a larger physicality and other testosterone-centric traits, which may increase their sexual attractiveness.

Granted, this is all correlational data, and there has yet to be any research that definitively tracks a patient being infected with T. gondii and then having a life-altering glow-up. It could also be possible that attractive people just like cats and are therefor more likely to become infected, or that very healthy people are just able to tolerate being infected with this parasite.

Researchers also didn’t find any significant differences in height, number of sexual partners or hand grip strength.

The bad: Negative effects of T. gondii

But before anyone starts volunteering to clean out their neighbour’s litter box, it’s also important to note the negative side-effects of being infected with this parasite. Research indicates that those infected have slower reaction times than average and a higher likelihood of getting into traffic accidents (thought to be a result of the poor reflexes.)

T. gondii is actually pretty dangerous to anyone with a compromised immune system. This includes babies born to mothers who were just infected with the parasite — coming into contact with the bug before the body’s immune system has had a chance to handle it can cause severe toxoplasmosis.

And while the weight loss in women is characterized as making them more attractive, this may actually speak more to the negative burden of carrying a parasite: more resources are taken by the infection, causing a female body to exert more energy. Weight preference varies by culture and eras, so while thinness may be considered a mark of attractiveness to some participants, it may not carry the same sexual benefit in other situations.

The ugly: Rats with a death wish

Humans aren’t the only hosts impacted by T. gondii. Previous research indicates that rats infected with the parasite may ignore ingrained survival tactics like avoiding areas where cats are present. Some cases even suggest that the predator-avoidance trait in infected rats can switch, causing them to become attracted to hungry felines. Why this is the case isn’t really known, however, previous research shows that the presence of this infection in rodents correlates with a significant increase in the metabolism of dopamine — how the brain absorbs this feel-good hormone — which could be connected to the rats suddenly liking the very animal that also likes to eat them. Theoretically this benefits the parasite. Since the parasite reproduces in the digestive tract of cats, it would need to somehow be swallowed by the cat to finish its life cycle — the poor rat be damned.


Emma Jones is a multimedia editor with Healthing. You can reach her at emjones@postmedia.com or on Instagram and Twitter @jonesyjourn.


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