A new study of the Black Death in London has concluded that the disease which wiped out perhaps half of the capital's population in the mid-14th century was not bubonic plague spread by the immigrant black rat from Asia ( The Black Death in London by Barney Sloane, The History Press Ltd 2011). When the plague struck in 1348 nobody had a clue about the nature of such diseases and it was only much later in history that there was speculation about the cause of the epidemic. I am not sure when the black rat and the flea it carried was first implicated but certainly there was no knowledge of the nature of bubonic plague until the nasty bug, Yersinia pestis, was identified in 1894 during an outbreak of the disease in Hong Kong. It is transmitted to humans by a flea that lives on a variety of rodents, one of which is the black rat.
When there was an outbreak of bubonic plague in India in 1994 I remembered that I had a book on my shelves by a zoologist called Graham Twigg which disputed the received wisdom that the black rat was to blame for the black death ( The Black Death: a biological reappraisal, Batsford 1984 ). On the one hand, said Twigg the small black rat ( rattus rattus ) is rather a timid creature and not the aggressive invader imagined by historians. It is a tree rat by nature and very acrobatic. I can vouch for that as I once arranged to film the only black rat surviving in captivity in England. It was kept by the firm Rentokil and I wanted to get a sequence of it for a wildlife film I was making. When we first went to see it, the rat did not look well, but demonstrated a little of its gymnastic ability. Sadly that was more or less its last performance and it died before we got the camera in.
Twigg argued that the spread of plague did not match the movement of the black rat and that descriptions of the disease did not tally that well with the symptoms of bubonic plague. He speculated that anthrax was a possible cause of the black death.
In 1994 when the Indian outbreak brought back the black rat story I got in touch with Twigg and researched an article which was published in the Independent in October. I spoke to Philip Zeigler who had written a book on The Black Death in 1969 in which what might be called the "classic" account of the origin of the 14th century black death was formulated. I summarised it in my article:
" It goes like this: bubonic plague was endemic in parts of central Asia before a series of natural disasters disturbed the ecology of the region and drove the rodents, fleas and bacillus westwards from their natural habitat. Ziegler wrote: 'It was, above all, rattus rattus, the tough, nimble, by nature vagabond, black rat that made the move.' Carrying the fatal flea, it invaded the Middle East and then Europe, reaching the south coast of England in 1348, perhaps on the ships of returning Crusaders."
Twigg had taught this to his students for many years before he began to question it. Why would an essentially tropical disease spread like that in a cold northern climate? And was it likely that the black rat, huddled into the artificial warmth of ships and houses, had enabled a disease to spread so fast. I put Twigg's thesis to a number of historians. Zeigler thought it interesting but most other historians brushed it aside. They were not about to re-open the case on the black rat. The little rodent is history now anyway, perhaps surviving in one or two ports and turning up now and again on ships. Our resident rat is the brown rattus norvegicus which is thought to have arrived around 1728, ushering in the Georgian era: another name for it is the Hanoverian rat. The brown rat is a ground dweller and burrower occupying a different niche from the tree loving black rat.
Bubonic plague has not gone away. There were major epidemics in the twentieth century, one in China which broke out among trappers who were infected by fleas in the pelts of marmots. Whether or not the black rat was responsible for the black death, it is certainly not regarded now as the first culprit when there is an outbreak of plague. It seems quite likely, too, that the black rat had nothing much do with the black death in London or elsewhere.