Your dog fleas are probably cat fleas. Human fleas are no longer that popular anymore, and with youngsters waxing pubic hair off with abandon, their little nature preserves are on the endangered list, at least in Los Angeles. Los Angeles has always been hip to fleas. As has all of California. The Spanish certainly were. Pulgas–fleas–pops up all over the map in this state. There was a whole Rancho de los Pulgas up in the Bay Area, one of the original Spanish land grants. Rich people live there now, making big money from little circuits no bigger than a flea. Not far away, ground squirrels host fleas that still carry the bubonic plague.

As scary as that name sounds, it is not the same plague that swept through Europe in the 1300s. That was a rat driven plague, the plague spreading to the human population because rats infected by the bacteria (Yersinia pestis) died and forced the rodent fleas to bite people, something they no doubt found distasteful but in a famine any host will do.

I don’t know who the fleas bit after all their human hosts died. Maybe no one, and they starved to death in little flea droves, hence ending the plague. It’s interesting that some parts of Europe were untouched by plague. Poland was spared almost entirely. But in other places–especially along the northern Mediterranean coast–the land was swept clean of humanity. You never know about fleas.

Think of it… Fleas had been feeding off rats happily for ages when somehow they became infected with the Yersinia pestis bacteria which, transferred from the flea’s stomach to the bloodstream of the rat, promptly killed the rat. Then the fleas, starving, leapt onto the next most common mammal, people, and killed them off. That left the fleas hostless and at the mercy of the frigid European winters. Death came quickly. And when fleas died, Yersinia pestis died with it.  The Black Plague was a disaster for everyone involved. People, rats, fleas and bacteria, everybody. Not a good business model.

Without doing any research at all, and in the true spirit of the Internet, I wonder what triggered this whole catastrophe. Maybe Yersinia pestis had been in rat guts for ages, but there’d been a genetic mutation–bacteria mutate at an astonishing rate–that suddenly rendered one gnarly. The flea it occupied then killed its rat host. Oops. The flea jumped ship. Another rat died. Meanwhile said flea was reproducing with the usual abandon, each baby flea carrying the mutated Yersinia pestis, and each killing its rat host. Every time a rat died the flea had to find another rat, and on and on. Soon rats are dying all over the place. Then people. I should mention that In people the plague could turn pneumonic, that is spread simply by coughing, no flea bite required at all, like a bubonic flu*. Then the thing really took off. All because some gene mutated just once in a Yersinia pestis . Again, I profess no expertise in this whatsoever. But this is the internet.

Or it could have been a parasite. I don’t mean the flea as a parasite, but something parasitizing the flea, a parasite within a parasite. Parasites make their hosts do strange things. Even a parasite with a bacterium for a host. Or maybe it was a virus that caused a change in the DNA of Yersinia pestis which rendered it fatal to rats and people. Again, this is baseless extrapolation, but this is the internet, and the weirdness of nature is fun to think about. But enough of this.

I think about fleas and I think about plague and am filled with terror. Then I remember that one of the Rothschilds, with all her money, was the greatest flea-ologist ever. Ever. She wasn’t even an entomologist (or more specifically, a siphonapterist), she just had a thing about fleas. Imagine her vast but tiny little collection. Imagine a Rothschild, with all her money, bounding after a flea bounding. The rich are different from you and I.

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* I’m leaving out the rarer septicemic variant, as it is simply too ghastly to think about.