Men infected with a common parasite transmitted by cats have been found to have higher testosterone levels than uninfected men. Maybe cats, not dogs, are man’s real best friend?

He’s cute, all right. And he may just have a little test-boosting surprise for you too (Ed: REALLY!?)


Cat Litter — The Unknown Test Booster

The likelihood is that, even if you don’t know what toxoplasma gondii is, you’ve got it. About half of all men do. And the longer you live, the greater the chance you’ll get it. One study from Holland claims that while just 20% of men in their twenties host the parasite in their bodies, that figure rises to 90% of men in their seventies.

Another thing you’re unlikely to know is that toxoplasma gondii infection appears to be associated with higher testosterone levels. Whether it actually causes them, however, is an open question. 

Before I go any further, it’s worth saying – in case you hadn’t guessed already – that I’m not advocating for you to go and get yourself infected with the parasite. Toxoplasmosis infection can be a very bad thing indeed, and is associated among other things with an increased risk of schizophrenia and delayed reaction times.

(22) Toxoplasmosis | Acquired vs Congenital | Signs, Symptoms, Diagnosis and Treatment – YouTube

Although the most common route for infection in humans is via cats, most toxoplasma gondii begins its life cycle in rats. Once an infected rat is eaten by a cat, the parasite passes into the cat’s intestines, where it reproduces frantically. Traces of the pathogen leave the cats’ body through its faeces, and then find their way into humans, usually via the mouth. Generally, this happens when gardening or cleaning a litter tray.

Apart from cats, another source is infected pork, especially if undercooked. Pigs are known to eat just about anything – you’ve seen the film Hannibal (2001), right? – and that includes rats.
Men with cat-litter disease are manlier

The lifecycle of toxoplasma gondii

A Czech study from 2008, in which saliva was taken from 174 women and 91 men, showed that infected men had significantly more testosterone in their samples, while infected women had less.

They also noticed that the normal pattern of testosterone fluctuation throughout the day was altered by infection with the parasite. Normally, a man’s testosterone is highest in the morning and then declines throughout the day, but this was not the case with the infected men, who saw a bounce in the afternoon.

The association between toxoplasma gondii and testosterone levels appears to be so strong that you can actually tell the difference between infected and uninfected men by looking at their faces. Seriously. In 2007, the same researchers did an experiment in which they showed pictures of men, some of whom were infected, to women. The women, who didn’t know who was or wasn’t infected, described the infected men as ‘more manly’ and ‘more dominant’.

Causality is always a difficult matter to establish. It isn’t clear whether having the parasite gives you higher testosterone levels, or whether higher testosterone levels somehow make you more likely to catch it. Testosterone is well known to modulate and can even suppress immune response, and so it could be possible that having high testosterone simply makes you more liable to catch the parasite.

Whatever the case may be, we recommend washing your hands after cleaning the cat litter tray.

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