Rat fleas were key players in Black Death
FLEAS WITH blocked guts were key players in the Black Death, the plague that swept through Europe in the mid-14th century. The pandemic waxed and waned in pockets until it finally died out in the 18th century. Experts believe that the number of people who fell victim to the disease's reign of terror ran into the high tens of millions with possibly more than half of the population of the continent perishing. Worldwide it has been estimated that over 100 million people probably died from the pestilence.
While a number of different life forms were involved in the plague the main players were the Black Rat, the Oriental Rat Flea and a tiny, rodshaped bacterium that has no English name but is known to scientists as Yersinia pestis. The leading medical and scientific experts at the time knew nothing of the sequence of events and attributed the cause of the Black Death to ' bad air'.
It is now known that the sequence of biological events began in China with Black Rats that harboured the bacteria but were resistant to the disease. The rats and their Oriental Rat Fleas travelled to Europe with traders either overland via the Silk Route or by sea in ships.
European Black Rats did not carry Oriental Rat Fleas and had no resistance to the disease. The invading fleas bred quickly in their new environment. The bacteria bred even faster and the defenceless European rats fell victim to the disease.
As the rats died they left a large population of starving fleas. In desperation the hungry fleas turned to feed on people. As the fleas sucked human blood the bacteria blocked each flea's mid gut preventing it from 'swallowing' the life-giving blood. In an attempt to clear its gut the flea regurgitated its meal back into its host thereby flushing the killer bacteria into the unfortunate victim causing him or her to die within four days.
In time, European Black Rats developed a resistance to the disease, the fleas stopped feeding on people, personal hygiene improved, the disease waned and the balance of life was restored.
It was long afterwards that scientists examining skeletons of plague victims in mass graves discovered DNA and protein signatures of Yersinia pestis and were therefore able to confirm that it was that bug that was behind the pandemic that caused such terrible human misery and suffering to so many unfortunate people so long ago.
- JIM HURLEY
