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Are Adorable Gerbils, Not Rats, to Blame for Black Death?

Feb 24, 2015 01:14 PM EST

During the 14th century, Europe was ravaged by what is commonly known as the Black death, or bubonic plague, and since then rats have largely been to blame. However, now new research finds that we have been pointing the finger at the wrong rodent.

According to researchers at the University of Oslo in Norway, giant gerbils of central Asia may have played a larger role in transporting the disease.

The Black Death, which originated in Asia, arrived in medieval Europe in 1347 and killed millions of people over the next 400 years, going down in history as one of the deadliest outbreaks. Epidemics broke out again and again, and it was believed that black rats were the cause, their fleas jumping to humans and causing infection.

Now, however, a new study reveals in the journal PNAS that climate conditions in Europe would not have been conducive to rat- and flea-driven disease outbreaks.

Asia, on the other hand, would have had wet springs and warm summers favorable for Yersinia pestis - the bacterial infection more commonly known as bubonic plague. This weather, the researchers say, would have caused a surge in numbers of giant gerbils, which are exceptional carriers of the disease.

"We show that wherever there were good conditions for gerbils and fleas in central Asia, some years later the bacteria shows up in harbor cities in Europe and then spreads across the continent," study author Nils Christian Stenseth, head of Oslo's Center for Ecological and Evolutionary Synthesis, told BBC News.

And because this was during a time when trade between the East and West was at an all-time high, the plague was probably brought to Europe along the Silk Road, according to Stenseth.

To reach their conclusion, the researchers compared tree-ring records from Europe with 7,711 historical plague outbreaks to see how the disease could have endured in Europe for so long. A rat reservoir, it turns out, was not the likely explanation.

"There are great individual differences, but many individuals can handle an absurd amount of plague bacteria," Oslo researcher Pernille Nilsson said in a statement. "Sometimes a single bacterium kills a mouse. Common rats can tolerate injection of 10,000 bacteria. Gerbils can tolerate 100 billion bacteria. That is ten million times as many bacteria."

Next, the team plans to analyze plague DNA from ancient European skeletons dating back to the Black Death period. If the genetic material shows a large amount of variation, it would add more weight to their gerbil theory.

Despite the fact that the bubonic plague left Europe after the 19th century, it can still be found in certain regions around the world. According to the World Health Organization (WHO), there were nearly 800 cases in 2013, 126 of them resulting in death.

What's more, traces of the Black Death were even found in NYC subways during a bacterial study earlier this month. But don't worry; the plague didn't contain any live fragments that could be harmful to humans. And researchers have yet to find any infected rats throughout the city - another finding that helps restore the reputation of these rodents.

As for cute gerbils, on the other hand, watch out!

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

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