DAN HOLDSWORTH: Not really cryptozoological, not quite anyway

Jon,


here's a link to some recent research on, of all things, the Black Death plagues of medieval Europe:

http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1001134

The article was linked off this one:


http://www.physorg.com/news206009200.html



which was linked into by Fortean Times.

The slight cryptozoological link was this: in the past quite a few epidemiologists have claimed (with not very much supporting evidence) that the only reservoir host for the plague bacterium Yersina pestis was the black rat, Rattus rattus, which is a mostly sub-tropical species and is somewhat beyond its northern breeding range in Britain. R. rattus in medieval times acted like it does now, as an imported pest in ports that couldn't quite cope with the climate here and only existed in ports from the population being continually topped up from shipping.

The way the disease was thought to spread was by infected rats transmitting the bacterium to their fleas. Once the rats died the now-starving fleas went looking for anything to bite, some bit people and thus passed on the disease. The problem with this model is that where rat-flea-human transmission goes on, you always see highly obvious mass deaths of rat populations before plague outbreaks; this was never commented on by medieval writers.

The logic goes that because R. rattus wasn't generally present in Britain there would be no reservoir host for Yersina pestis in Britain; therefore it couldn't be the cause of plague; therefore we would have to look for another causitive agent. The favourite for this was an entirely inferred cryptid, an unknown haemorrhagic virus. This is seriously scary because viruses are very difficult to kill; one with a symptomless incubation period of weeks is incredibly scary.

This research, then, is actually very reassuring news: we lose a seriously scary cryptid disease and replace it with a known bacterium that can be treated. We also learn something because that research shows that one strain of Y. pestis spread up to Norway, then down south again. There's no way it could have been ticking over in black rats up there, so there must be another reservoir host (domestic cats, possibly; they are easily infected and cat fleas readily bite people as well) or the disease there acted more slowly and simply spread from person to person.

This won't happen again, if only because people now have access to high quality insecticides and don't tolerate flea infestations, so the transmission chain gets broken. I'm not sure that this qualifies as cryptozoology, but it does qualify as gold-standard debunking of a scare story, replacing a scary myth with something that's still nasty but eminently treatable.

Dan Holdsworth.