http://www.bbc.co.uk/news/science-environment-31600703
http://www.bbc.co.uk/news/science-environment-31588671

When you discover that, across the last 800 years, gerbils helped spread bubonic plague and thus were responsible for helping to kill 200+ million people in Eurasia alone, your attitude to gerbils may change. It is perhaps best that we point out up front that these agents of death & destruction are Great Gerbils (see bottom), and not the Mongolian Gerbils (Meriones unguiculatus, pictured above) that most folks keep as cute pets. However, we should also point out that gerbils form part of the animal order Rodentia, and used to be called “desert rats”, which puts us straight back close to the lap of the Black Rat (more later).

Gerbil odd info:

It is illegal to purchase, import, or keep a gerbil as a pet in the US state of California; this is claimed to be due to the threat they pose to indigenous ecosystems and existing agricultural operations.

A recently-released PNA Submission has been picked up by almost every UK newspaper, probably because of the connection with gerbils (so much friendlier than rats). Then again, let’s face it: the subject of the research (“Climate-driven introduction of the Black Death and successive plague reintroductions into Europe”) needs something friendly to offset the sheer horror of it’s topic.

Bubonic Plague

There have been 3 waves of bubonic plague pandemics known so far:

1. Plague of Justinian (541–542)
   This affected the Eastern half of the Holy Roman Empire and returned periodically until the 8th century. It was named after the Eastern Roman Emperor Justinian I, who was emperor at the time of the initial outbreak; he contracted the disease himself yet survived. It is estimated that 25 million people died in the original outbreak, and 50 million across the first 2 centuries.
   
   

   

2. The Black Death (1346 - 1353)
   This was first reported in Crimea in 1343. It spread rapidly throughout the Black Sea & Mediterranean, then south into Turkey (1347), south into North Africa & north throughout Europe (1349), Scandinavia (1350) & Russia (1353). It recurred occasionally in Europe until the 19th century. It is estimated that upto half of the European population died across 4 years (80% in southern Europe, 20% in northern Europe) (min: 75 million, max: 200 million across Eurasia). The scale & nature of the death & misery involved in such a short period of time is almost impossible for us to conceive.
   
   The name ‘Black Death’ was because blood vessels burst under the skin, then the flesh died & turned black (with the same necrosis of the hand as in the first pandemic). An alternative name of ‘Bubonic Plague’ was due to the buboes (gavocciolos, or hard, round swellings) which appeared within the groin, neck and armpits (located due to the lymph nodes concentrated there). If the bubo discharged the puss that it contained then the person had a chance of recovery. Most died. A contemporary account by the Italian writer & poet Giovanni Boccaccio is chilling:-
   

   In men and women alike it first betrayed itself by the emergence of certain tumours in the groin or armpits, some of which grew as large as a common apple, others as an egg...From the two said parts of the body this deadly gavocciolo soon began to propagate and spread itself in all directions indifferently; after which the form of the malady began to change, black spots or livid making their appearance in many cases on the arm or the thigh or elsewhere, now few and large, now minute and numerous. As the gavocciolo had been and still was an infallible token of approaching death, such also were these spots on whomsoever they showed themselves.

   There was also a pneumonic form of the disease that caused breathing difficulties & killed the victim in 2 days (far, far quicker than the bubonic form).
   
   

   

   So many people died so quickly that burying the corpses became a logistical difficulty. At first, the authorities used the existing graveyards. These quickly filled and, later, the “authorities” were themselves dead. Eventually, all bodies were simply dumped in hastily excavated pits; every large city--and many small towns--in Britain has one or more of these (Hull suffered plague in 1635 for 3 years, with more than 2,000 people reported to have died; a later 1665 plague had a plague pit where the city-centre railway station now stands; I clearly recall being told that a 10ft (3m) bank in the cemetery on Spring Bank West was a plague pit [Hull is perfectly flat everywhere, so any rise in the land is surprising]). As the largest city in England, London had a further problem. The whole of the city became littered with very large plague pits. Then, later, when the Underground was built, many of the upper-level routes passed directly through, over or under these pits (Aldgate Station; Bakerloo Line, London Depot, near Elephant & Castle; Green Park; Hyde Park; Moorgate & many others).
   
   One side effect of The Black Death in England was the appearance & rise of the Freeman, a third layer of society. Europe had Rulers; if you were not a member of the ruling class then you were a peasant, and peasants were the lowest of the low. Examples? How about droit du seigneur, the local lord’s right to take the virginity of every girl when she reached puberty? There are ever so many others. In England, so many peasants died from the Black Death that labour became scarce. That allowed former peasants to sell their labour as day labourers. Then if, one day, they did not like their master they could find another master the following day. In this way a whole section of society of free men arose, which utterly transformed England.
3. The Third Pandemic (1855 - 1959)
   This began in south-western China & ultimately spread to all inhabited continents, with an estimated loss of 12 million people in just India and China.

   

   Perhaps the greatest significance of the 3rd Pandemic was the isolation of the bacterium responsible for the pandemics + the beginnings of an epidemiology. The Swiss-born French bacteriologist Alexandre Yersin is credited with it’s discovery whilst working in Hong Kong in 1894; the Japanese physician and researcher Kitasato Shibasaburō also independently identified the same bacterium at the same time & place. Both investigators reported their findings, but a series of confusing and contradictory statements by Kitasato eventually led to the acceptance of Yersin as the primary discoverer of the organism. In 1967 the bacterium was renamed Yersinia pestis in honour of Yersin. Finally, in 1898 French researcher Paul-Louis Simond demonstrated the role of fleas as a vector. It is this last route with black rats as the primary epidemiology for the pandemics that is called into question by this latest research.

Ever since the end of the 17th Century, the common medical belief has been that Rattus Rattus (the black rat) has been the principal vector for Yersinia pestis, ably assisted by rat fleas. It has also been assumed that rats acted as a reservoir in Europe for the disease between outbreaks.This latest research published via PNA suggests that both of these assumptions are wrong.

The researchers have made use of:-

1. a dataset of 7,711 geo-referenced historical plague outbreaks
2. 15 annually resolved tree-ring records from Europe and Asia

The conclusions are that:-

1. the plague reservoir is in Asia
2. the animal vector is most likely to be giant gerbils (Rhombomys opimus, also called great gerbils)
   (this animal is notorious for it’s ability to host bacteria + viruses)
3. there is a statistical correlation between weather that causes a large increase in gerbil (+ gerbil flea) numbers and resurgence of plague in Eurasia.
   (warmer springs and wetter summers cause a large population increase in great gerbils + their fleas)
   (there is ~15 year delay between the Asian gerbil population increase & European resurgence of plague)
4. a collapse in the inflated gerbil population would cause the fleas to seek new hosts
5. those fleas would get carried along existing trade routes from China to Europe, such as the Silk Road

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Alex Kemp