It was a group of Asian rats that ended the plague in Europe that killed 25 million people.

Since the 14th century, a plague pandemic that swept Europe and other parts of the world has killed some 25 million people, and has since occurred several times, afflicting Europe for four centuries. By the 18th century, an earthquake in India had led to a surge in the number of rats in the area, which eventually migrated to Europe. It was these mice from Asia that ended the plague epidemic in Europe. The Italian edition of Scientific American restores the history of how Asian rats ended the plague in Europe.

It was a group of Asian rats that ended the plague in Europe that killed 25 million people.

In The city of Astrakhan, the dusty streets are crowded with horse-drawn carriages and cattle carts, and camels are teetering around full of goods. From time to time, Russian, Hindi, Arabic, Turkish, Chinese, Mongolian, English, Dutch and Italian are heard. In the air, the smell of faeces, animal and human sweat skunk is mixed with the flavours of spices, freshly made leather, fermented cheese, cured meat, wine, perfume and fennel. Towards the river, the roar of cars and the cries of the drivers were gradually drowned by the roar of hammers, axes and saws in Tsar Peter the Great’s shipyard. The huge river, the Volga River, divides Russia’s north and south, running thousands of meters and eventually into the Caspian Sea. The port on the Volga River is the only way for all.

After months of travel, caravans from the East arrived at the pier with raw silk, spices, rice, dried fruit, coffee, wine, saffron, sulfur, and fuel, gold, silver and pearls. Two weeks ago, lorries from the West unloaded soap, sugar, needles, cloth, velvet, glassware, mirrors, stationery, corn, butter, cheese, sausages, wine, cognac, spirits, furniture, hardware and clocks from a European sailboat in the Dardanelles Channel before leaving the Port of Crimea in the Black Sea. Goods from Europe or Russia are shipped to the east by caravan. The cargo bound for Russia follows the Volga River up the countercurrent, sails for tens of thousands of kilometres before heading for the Don River and heading for the Black Sea, or by land, to the port of Crimea.

This was the ordinary day of Astrakhan in 1727. By this time, the Persians had been repulsed by Peter the Great, and Asdarahan had just restored its glory as the ancient center of the Silk Road.

At night, when the bustling crowd receded and the truck and cargo ship left, a huge gray patch took over the river, like a drop of oil on the water. These patches are hundreds of meters wide and sway with the waves. These “islands” are packed with millions of frenzied objects: they swim firmly to the opposite shore at a distance of 500 metres, leaving them to be washed south by rivers. As soon as they reached the banks of the West Bank, which belonged to Europe, they disappeared, just as they had quietly appeared on the banks of the East Bank of Asia. Thousands of meters south is the corner of the river, where the water is stagnant and the gray “islands” are stuck here, revealing their mystery: thousands of rats drown edged there because they fail to reach distant river banks.

Astrakhan residents, as well as Russian chronicler Alexis Turgai, have observed this phenomenon and recorded how a large group of rodents made the “long journey” from the east into the West.

The last step

For several days, rats waded through the Volga River and waded in Ukraine several times. The rats first crossed the Dnieper River (with a large number of deaths) and finally through the Bug and Transnistrian rivers. In winter, rats are seen trotting along the frozen river. A few years ago, a powerful earthquake struck India, causing a surge in the number of rats, which in turn triggered migration. In the hours before the earthquake, the rats felt the rising gas from the ground, escaping their underground nests and running toward the open. Humans are not so lucky. The ruins buried not only food, but also many human bodies. At first, large amounts of food sources led to a surge in the number of rats, which was followed by mass migration.

The rodent migration of 1727 ended the epidemic plague that had plagued the old continent for four centuries. Just a few years ago, in 1720, the last outbreak of the plague, which had hit Europe countless times, lasted two years.

The outbreak of the plague was caused by the crew’s failure to comply with the 40-day quarantine regime established by the city of Lagusa (now Dubrovnik, Croatia) three years later, which was initiated in 1374. In response to regular outbreaks at various ports, the Republic of Venice began to refuse to allow “suspicious” vessels. But it was soon discovered that a “non-suspicious” ship could cause the Black Death, even if the huge commercial profits from the rejected goods were abandoned. Thus, in 1377, the Fifth Maritime Republic (whose name emphasized the extent of trade at the time) established the first infectious disease hospitals. All crew members and passengers, even in good health, must stay on the hospital island in front of these ports for a month. This preventive measure has shown results and has been adopted by all mediterranean ports within a few years. Soon, the stay became 40 days. Because according to Hippocrates’ theory, acute diseases (e.g. plague) can show signs within 40 days, otherwise they are chronic (and therefore can be inferred not plague).

It was a group of Asian rats that ended the plague in Europe that killed 25 million people.

Plague epidemic. This painting by the French painter Jacques Rigaud depicts the plague that struck Marseille in 1720 and killed 40,000 people (half of the city’s population) in two years

The number of days in the “40-day quarantine period” actually has historical origins, especially in the Middle East. At the time, 40 days was thought to bring soul purification and repentance, as well as redemption. Astronomers in Mesopotamia associate “40” with the Pleiades, whose constellations are invisible for 40 days between April and May and can cause spring water or flooding. Although floods are often catastrophic, they are vital to agriculture. So throughout the ancient world, and in later Judeo-Christian traditions, this period represented an inescapable difficulty, suffering and repentance, and at the same time prepared for the arrival of something joyful – 40 days after the Great Flood, Moses listened to God’s mouth on Mount Sinai, Jesus rose to heaven after the desert fast (which led to the development of the Tetra Igo for Easter).

A year ago, the three-masted merchant ship, the Grand Saint Antoine, set sail from Syria and arrived at the port of Massei on May 25, 1720, in preparation for a 40-day quarantine period. Despite the deaths of eight sailors on the trip, the ship’s owner requested an exception because the precious fabric on board could not wait until 40 days later to trade. On June 5, 1720, the Great St. Antoine docked at the port, and the plague and cloth landed together. Rats that came ashore by cable, as well as fleas on cloth and mice, brought germs ashore. Based on the more credible assumptions, we speculate that some healthy carriers or newly infected sailors who have not yet shown symptoms simply don’t care about the isolation period, and after a year-long sea voyage, they go straight to the local tavern. Massey lost 40,000 residents in two years, half of the city’s population. A total of 120,000 people have died in southern France, more than a third of the region’s population.

It was a group of Asian rats that ended the plague in Europe that killed 25 million people.

During the plague of Mace in 1720, priests comforted dead patients. The painting was painted by the French historical painter Nicolas-Andr? Monsiau

Since then, the plague has appeared many times. In Europe, the most serious and recent plague epidemic occurred in Messina, Sicily, in 1743, mainly because of the failure of cargo ships to comply with the quarantine regime. The ship was one of many ships from the Ottoman Empire, which docked in Sicily and was declared a free port by the Bourbon dynasty in 1734 in an effort to promote economic development.

On March 20, 1743, a Genoa merchant ship was bound for Messina with grain and cloth ,ideal habitat for rats and fleas. Despite the health supervisor’s discovery that a sailor had died on board, the merchant ship was granted permission to berth and disembark the crew. The captain, Jacopo Bozzo, claimed that the sailor’s death was due to trauma, and that the evidence was a number of slightly black spots on the deceased’s body. Over the next few days, other sailors and the captain appeared on the same spot and later died. This fact breaks the lie, but it’s too late. In just a few months, 70 per cent of the inhabitants of Messina died, half the total population of 50,000 in the Region of Reggio Calabria. But unlike the plague pandemic that broke out in Messina in 1347 and afflicted Europe for nearly five years, known as the Black Death, this time it did not spread.

The most successful species

In the summer of 1727, the group of rat rattus norvegicus, which waded across the Volga River to Asdarahan, succeeded. Like the previous plague protagonist, Rattus Rattus, the brown house rat can be infected with the plague bacteria and is the host of the plague bacteria. But the one that lives on the brown mouse is a different flea, the horned leaf flea, which is more “loyal” to the host. Unlike Xenopylla cheopis, which lives in black mice, when brown-family mice die from plague or other causes, horned leaf fleas rarely transmit infections in their mouths from their hosts to humans, because horned fleas are not interested in humans and only live between rats. As a result, plague bacteria are confined to the brown-house rat population.

If the bacteria cannot be transmitted to humans through flea bites, the chances of infection are greatly reduced. At this point, germs can only infect the human body through food contamination or an environment with feces and urine. When the bacteria infect a human lung, it can be transmitted between humans through breathing. The flea-based plague epidemic was halted after brown-house rats led to the extinction of black house mice.

Compared with the black house mouse, the brown mouse is stronger, witty, aggressive, and more cooperative. They are skilled in swimming and particularly enjoy living in hot and humid environments. In contrast, black rats prefer to stay in a dry environment, usually on rooftops or in barns. Rats found on the Volga River are probably not the first brown-house mice to migrate, as brown-house mouse bones were found in Europe as early as 1727. But from the 18th century onwards, the environment in Europe became very hot and humid, providing a lot of breeding opportunities for brown rats. The number of brown house mice multiplied and flocked to the territory of the black house mouse to steal their food.

It was a group of Asian rats that ended the plague in Europe that killed 25 million people.

Paris was the first city to build an underground sewage system, which opened in 1374 and started on Montmartre with a very slow pace until it was completed in the 18th century. Since then, large cities in Europe and the United States have also begun to build underground sewage systems. It was also during the same period that the first brown rats began to appear in these cities. Brown rats were first discovered in England in 1730, in France in 1735 and germany and North Africa in 1740. Brown house mice appeared in Spain late, and were not first discovered until 1800. The brown rat is also known as the Norwegian rat because of the British naturalist John Berkenhout’s 1769 outline of the Natural History of Great Britain Britain called the mice “Norwegian rats.” At the time, Beckenholt found these new illegal immigrants, the brown house rats, in some sailboats from Norway.

Today, brown rats have become the most common mouse and one of the most successful species after humans. With the exception of Antarctica, Alberta in Canada, and some nature reserves in New Zealand, brown rats can live anywhere on Earth.

Rats and fleas

On July 14, 1914, a paper published in the London Journal of Health confirmed for the first time that the chances of the plague being transmitted to humans by fleas that live in brown mice were low. From 1909 to 1913, C. Strickland, a lecturer in biology at the University of Cambridge, was a lecturer in biology. Professor Strickland has been studying the fleas and wrote and submitted a 13-page report in early 1914. The names of the three volunteers who provided forearms to study horned leaf fleas were recorded in the form of acronyms, namely E. H, G. M and C. S.

Strickland first raised fleas in a glass cage filled with rats. After many experiments, he found that a mixture of food residues and rat excrement dropped on the floor was the most popular nutritional food for fleas. Strickland then observed the growth cycle of fleas: from eggs hatched into larvae, to larvae, to adult worms that can jump and suck blood over long distances. The growth cycle of horned leaf fleas is 84 days. Among them, the eggs take 7 days to hatch as larvae, and the larvae stage lasts 60 days. At this stage, Strickland records, “the larvae have a strange habit of devouring the skins that have been shed at different stages of their own.” The larvae need to grow for 17 days after they are turned into larvae. The time for all stages here is average, and the length of time for each phase does not have much to do with the environment. The larvae grow in the food residue on the ground, and pregnant fleas are moved to a black cloth so that the white eggs they give can be easily distinguished.

In this experiment and another experiment involving three volunteers, biologists at the University of Cambridge observed, measured and summarized other characteristics of the horned leaf flea: about 2 mm long, able to jump 9 cm tall in full ness (45 times its length) and 12 cm tall (60 times its length) when not sucking blood; They can also crawl up to 24 cm up on a vertical glass. The fleas can survive for up to a month without any food, but 17 months if organic waste and rat waste are present. This explains why rats have never been able to get rid of fleas that live on them.

To study the relationship between horned fleas and mice, rabbits, and humans, the researchers first transferred horned fleas from domestic mice to new hosts. In this process, horned fleas can choose between mice and other hosts: horned fleas are placed in the center of a 6 cm-long glass pipe, with a rat at one end and a mouse, a rabbit, or a human arm at the other. In addition, the experimenters carried out the experiment on the blood of mice and fleas that had been fasting for a day. Observations showthat that the horned leaf fleas have no preference in host selection. However, when placed or stayed on a person’s arm, they do not bite immediately, as they did in mice, but usually wait at least a day. In other hosts, the flea will die in a few months without breeding. In addition, gender can influence the behavior of the flea: male horned fleas only begin to search for females after they suck the rat’s blood, which can give birth to about 400 eggs within 24 hours after conception. “It is clear that only rats have substances in their blood that activate the reproductive organs of male and female keratins,” Strickland concluded. In other words, the continuation of the species of rat-to-angle leaf fleas is indispensable. “


With the presence of millions of mice and fleas that live on them, plague bacteria can always find suitable breeding and spreading. Poor public health and hygiene conditions shorten the distance between humans and mice, so the plague bacteria can be transmitted to humans. The bacteria can also be transmitted through the bites of air or fleas, which are rare but still likely to remain. Indeed, the plague has not been completely eliminated. Over the past 15 years, the World Health Organization has received reports of more than 34,000 cases of human plague infection from 24 countries. These plague outbreaks are usually mild and short-lived, with Asia and Africa occurring most often, followed by the American continent (including North America). The endemic plague in Madagascar has several cases each year, most recently in early 2018. The plague outbreak, which has seen hundreds of cases, occurred during the Vietnam War, in the 1970s.

In Italy and throughout Europe, the plague last appeared in 1944. At that time, a British ship from Malta entered the port of Taranto, which had just become an Allied naval base, carrying scrap and tampons, which would be made into second-class fabrics. During the voyage, a sailor died of plague, but the captain, instead of reporting the incident, obtained permission to berth, unload and disembark. A few days later, in late 1944, the first cases of plague infection occurred within the military, and then the citizens were infected.

It was a group of Asian rats that ended the plague in Europe that killed 25 million people.

In 1720, the plague began to spread from the port city to southern France, killing 12,000 people, more than a third of the local population.

The Allies immediately suppressed the spread of the military secret, so the panic did not spread throughout the city. At the same time, in support of Italian military doctors, the British brought in Indian doctors who knew a lot about the plague, which was still occurring in some parts of India, as well as two british doctors who were responsible for rodent eradication at London’s River Pier and British doctors who excelled at using new technology. New technologies to combat plague include enemy fear against fleas, penicillin for anti-infection and anti-plague vaccines. In fact, the plague vaccine was proved to be of little use at the time. Even today, there is still no effective and safe vaccine against plague available to the general public.

The plague chain was controlled and interrupted within four months. In the end, there were 30 cases among the military and citizens, 15 of whom died. In 2004, a street in Taranto was named Umberto Montedoro Street in memory of all the doctors who fought together to fight the plague.