The BIG Pox - Syphillis.

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April 29, 2008

Essay

 

A Great Pox’s Greatest Feat: Staying Alive

 

 

By MARLENE ZUK

 

http://www.nytimes.com/2008/04/29/health/29essa.html?th & emc=thThe findings were hardly

earth-shaking. They dealt with an obscure bacterial infection found in

an equally obscure group of natives in Guyana. Nonetheless, they made

headlines.

Why? Because the disease was syphilis.

The new research suggested that syphilis originated as a skin ailment

in South America, and then spread to Europe, where it became sexually

transmitted and was later reintroduced to the New World.

The origin of syphilis has always held an implied accusation: if

Europeans brought it to the New World, the disease is one more symbol

of Western imperialism run amok, one more grudge to hold against

colonialism. Sexually transmitted diseases

have always taken on moralistic overtones — they seem like the price of

pleasure. We tell ourselves that if we can just make everyone behave

responsibly, we can halt the attack.

But we may not have as much say as we might like to think. Infectious diseases

are caused by living beings that spread from one host to another, and

natural selection will favor anything that increases that spread — say,

a higher probability of becoming airborne, or a better means of

attaching to the gut wall.

The syphilis bacterium, Treponema pallidum, has no nervous system or

brain, no consciousness with which to plot an attack. But it has an

ability that is even better: it can reproduce at a rate that leaves us

in the evolutionary dust. For any S.T.D., making the host more likely

to have sex will benefit the pathogen that causes it. And syphilis may

be a case in point.

Detailed records of syphilis infection start appearing in Europe from 1495, and a fearsome disease it was. Smallpox

was called smallpox to distinguish it from the great pox, syphilis,

which evoked this description from Ulrich von Hutten in 1519: “Boils

that stood out like Acorns, from whence issued such filthy stinking

Matter, that whosoever came within the Scent, believed himself

infected. The Colour of these was of a dark Green and the very Aspect

as shocking as the pain itself, which yet was as if the Sick had laid

upon a fire.â€

Two points are noteworthy about this vivid account. First, it

contrasts markedly with modern experiences with the disease. Although

serious in its overall effects — which can include heart problems,

brain damage and infertility — the rash and other overt symptoms of

syphilis are now much more muted, and the disease may go undetected for

some time, which helps explain why it is so hard to control. Second, it

is reasonable to suppose that a sufferer of the symptoms von Hutten

describes would be unlikely to get a lot of dates.

These two observations led Rob Knell, a scientist at Queen Mary

University in London, to propose (in a 2004 paper in The Proceedings of

the Royal Society of London) that they were connected. If a

syphilis-ridden individual were less likely to have sex, and hence

spread the disease, it would behoove the disease organism to evolve a

less acute effect on its hosts. Syphilis became less severe, he argued,

because it was transmitted more readily if victims were still

attractive to the opposite sex.

And while these changes were too rapid to be attributed to humans’

evolving resistance to the disease, he continued, for the syphilis

bacteria, even a few years represents many thousands of generations. So

we have syphilis itself to thank for the lessening of its symptoms. The

disease is still serious, of course. But the rapid evolutionary change

is striking.

Conventional wisdom used to hold that all diseases eventually

evolved toward a more benign state, a “don’t bite the hand that feeds

you†rationale. The muting of syphilis notwithstanding, we now realize

that is not the case.

Diseases can evolve to become more virulent, more benign or neither

— it all depends on what’s in it for them. For some diseases — cholera,

for instance — killing the host is immaterial if the pathogen can

spread via contaminated water sources.. But sexually transmitted

diseases must get around via sex. From the pathogen’s perspective,

simply sitting around in the intestinal tract waiting for a too cursory

bout of hand washing is unsatisfactory.

The disease organism from which syphilis arose is spread through

simple skin contact. In chilly Europe, that’s too chancy a mode of

transmission. Sex, on the other hand, is a fairly reliable means of

transport, even for a delicate bacterium.

So you might blame Columbus, not for wreaking havoc on the New World

through the spread of a sexually transmitted infection, but for wearing

clothes. If he and his fellow Europeans had been more prone to going

about au naturel, maybe the great pox wouldn’t have been so great after

all.

Marlene Zuk is a

biology professor at the University of California, Riverside, and

author of “Riddled with Life: Friendly Worms, Ladybug Sex and the

Parasites that Make Us Who We Are.â€

 

 

 

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