Sexually transmitted infections selfishly increasing your sexiness

We have not yet begun to scratch the surface of how pathogens and other bugs can manipulate behavior. This is also a major cost of infection that many people don’t even consider; our personalities are no doubt shaped in part by our current and past infections and our microbiome.

Treponema_pallidum

In The Selfish Gene, Dawkins speculates that sexually transmitted infections, in order to spread as far and wide as possible, could increase the libidos of their hosts:

I do not know of any direct evidence that sexually transmitted diseases increase the libido of sufferers, but I conjecture that it would be worth looking into. Certainly at least one alleged aphrodisiac, Spanish Fly, is said to work by inducing an itch . . . and making people itch is just the kind of thing viruses are good at. (Dawkins 2006 pg. 247)

Recently I came across an amazing example of syphilis doing just that in Oliver Sacks’ “The Man who Mistook his Wife for a Hat” where a 90 year old woman who had a primary but suppressed syphilis infection tests positive for neurosyphilis in her spinal fluid:

A bright woman of ninety, Natasha K., recently came to our clinic. Soon after her eighty-eighth birthday, she said, she noticed ‘a change’. What sort of change? we queried.

“Delightful!’ she exclaimed. ‘I thoroughly enjoyed it. I felt more energetic, more alive—I felt young once again. I took an interest in the young men. I started to feel, you might say, “frisky”—yes, frisky.’…

‘My friends started to worry. First they said, “You look radiant— a new lease on life!”, but then they started to think it was not quite—appropriate. “You were always so shy,” they said, “and now you’re a flirt. You giggle, you tell jokes—at your age, is that right?”
‘And how did you feel?’
‘I was taken aback. … “You’re sick, my dear,” I said to myself. “You’re feeling too well, you have to be ill!” ‘It was something in my body, my brain, that was making me high. And then I thought— goddam it, it’s Cupid’s Disease!’

‘Cupid’s Disease?’ I echoed, blankly. I had never heard of the term before

‘Yes, Cupid’s Disease—syphilis, you know. I was in a brothel in Salonika, nearly seventy years ago.  I caught syphilis—lots of the girls had it—we called it Cupid’s Disease. My husband saved me, took me out, had it treated. That was years before penicillin, of course. Could it have caught up with me after all these years?’

There may be an immense latent period between the primary infection and the advent of neurosyphilis, especially if the primary infection has been suppressed, not eradicated.

When Natasha is offered treatment she says:

‘I don’t know that I want it treated,’ she said. ‘I know it’s an illness, but it’s made me feel well. I’ve enjoyed it, I still enjoy it, I won’t deny it. It’s made me feel livelier, friskier, than I have in twenty years. It’s been fun. But I know when a good thing goes too far, and stops being good. I’ve had thoughts, I’ve had impulses, I won’t tell you, which are—well, embarrassing and silly….I don’t want it cured… I wasn’t fully alive until the wrigglies got me. Do you think you could keep it just as it is?’

Ultimately, they do treat the infection but Natasha K. gets her wish, the changes she loves are maintained. This case study is more interesting because of Natasha K’s age and the latency of the behavioral effects which may make it more likely that the increased libido is an effect of the neurosyphilis rather than the characteristic that made her more predisposed to acquire syphilis in the first place. But other aspects of Natasha K’s personality could also increase her attractiveness as a sexual partner in the interests of the syphilis bacteria. One hypothesis (most notably forwarded by Miller) is that both sexes advertise their quality by doing expensive complicated things in courtship with their brains including being funny, fascinating and creative. Was syphilis merely evoking simple disinhibition causing Natasha K.’s intrinsically witty and energetic character to bubble up or can syphilis cause someone to  be more creative? Sacks also describes another patient with neurosyphilis, Miguel O. (pg 54) who is “simple”, unable to express himself well in words and with speech and hearing deficits. Throughout the book Sacks evaluates patient mental states by asking them to draw, and he does this with Miguel O.:

I asked him to copy a simple figure (Figure A) he produced, with great brio, a three-dimensional elaboration (Figure B)–or so I took it to be, until he explained that it was ‘an open carton’, and then tried to draw some fruit in it…An open carton, a carton full of oranges–was that not more exciting, more alive, more real than my dull figure?

open and closed carton

A few days later I saw him again, very energized, very active…I asked him again to draw the same figure. And now, impulsively, without pausing for a moment, he transformed the original to a sort of trapezoid, a lozenge, and then attached to this a string—and a boy (Figure C). ‘Boy flying kite, kites flying!’ he exclaimed excitedly.

kite

The picture to the left also shows how the man reproduced the figure once he had been treated, this is smaller and more faithful to the original, with less creativity. It is possible, as Sacks points out that syphilis has an effect similar to administering L-dopa which also causes creative flourish in patients. But this is a proximate explanation; why would syphilis increase the rate and degree to which humans engage in creative flights of fancy? Has syphilis evolved to improve the sexual success of its victims in this way? Given that females are the choosier sex could we predict that syphilis would cause relatively greater sexual disinhibition in females and more elaborate courtship displays in males?

There are several famous cases of syphilis in creative genius. For instance this article speculates that neurosyphilis might have created spikes in the creative output of Schubert, Schumann and Wolf, famous German composers. Pathogens can have remarkably specific influence on host organisms. Here you can check out a recent lecture I gave on pathogen host interactions here at the University of Portsmouth including this video showing a man with rabies afraid of water (perhaps because the rabies virus does not “want” to be diluted in the saliva). Humans may be a bit more difficult to control than, say, a caterpillar but if I was syphilis and trying to spread from person to person I might direct the creative output to sexier forms like the tango or dirty limericks. Given that syphilis may have only been around for hundreds of years it’s done pretty well.

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One thought on “Sexually transmitted infections selfishly increasing your sexiness

  1. The more direct approach is simply to increase the host’s fertility, never mind influencing behavior. Cf. http://www.bbc.com/news/health-34857022

    Albeit decreasing the host’s fertility might also prove useful depending on the parasite. Both the roundworm and the hookworm results as described could be evolved strategies for enhancing reproductive prospects for the parasite. If the hookworm requires a strong and healthy host, the debilitative effects of its own infection could downgrade the suitability of its host’s offspring as candidates for subsequent infection – thus, by suppressing fertility, it could be insuring that only uninfected hosts reproduce, thereby insuring for itself a ready supply of healthier candidates. It may be that the roundworm, for its part, can afford to be less picky, so that simply boosting the host population’s overall rate of reproduction turns out to be a workable strategy in that case.

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