Monday, February 23, 2015

Rats Declared Innocent Over Black Death

Rats exonerated over Black Death

If you know that plague killed millions of people in medieval Europe than you will realise how relieved rats must be to read this. That is if they can read of course... #Hehehe

A Norwegian-led study has dismissed the widely accepted idea that Europe’s rats became infected with plague-carrying fleas that killed up to 200 million people over the following five centuries.

Rather, the researchers believe the pandemic was repeatedly reintroduced to Europe by traders travelling from near modern day Pakistan.

The study, published this morning in the Proceedings of the National Academy of Sciences, offers a “new perspective” on the transmission of plague-causing bacteria across Eurasia.

Rather than “a single introduction at the time of the Black Death” — the catastrophic 1340s outbreak that wiped out around a third of Europe’s population — the pandemic was repeatedly triggered by “a climate-driven intermittent pulse of new strains arriving from Asia”, the paper says.

“Our analysis finds no support for the existence of permanent plague reservoirs in medieval Europe.”

The paper says bacteria-carrying fleas normally live in the fur of small rodents such as gerbils, Altai marmots and long-tailed ground squirrels — all native to Central Asia — as well as the more ubiquitous rats. It says the fleas only go in search of human hosts when rodent populations go into steep decline, usually because of sudden shifts in the climate.

The research team scoured the historical record for rodent “reservoirs” that would have been capable of consistently infecting Europeans. It crossmatched a database of over 7700 plague outbreaks in Europe between the 13th and 19th centuries with climate change records across Europe and Asia.

After ruling out plague outbreaks likely to have been caused by infected visitors from nearby areas, the researchers came up with a list of just 16 spontaneous epidemics. None of these coincided with climate fluctuations in Europe.

But most occurred 15 years after climate shifts in the distant Karakorum mountain range of northern Pakistan, which were near medieval trade routes. “A plausible suggestion is that caravans were responsible for transporting plague between Asia and Europe,” the paper says.

“Camels are known to become infected relatively easily from infected fleas and can transmit the disease to humans.”

The paper says the findings explain how the Bubonic plague kept appearing in Europe even though large tracts of the continent had no rats.

It says its conclusions could be confirmed by analysis of ancient DNA of the plague-causing bacteria, Yersinia pestis, from the remains of European plague victims.

Source: The Australian

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