Rat Officers

Written by Rida Raza, Courtney Chambers, and Sheyla Nguyen

rat dipping
Rat-catchers dipping rats. Photograph. (1900/1920). Credit: The Wellcome Library London.

I. Introduction. Written by Sheyla Nguyen

There were many wild animals that lived in London because the man-made environment met their every need. These animals were part of daily life in modern London, and were mentioned frequently in the Medical Officer of Health Reports because they were regarded as a nuisance and a health hazard. One of the wild animals that lived in intimate proximity to human Londoners was the rat. Rats were a huge problem in 19th- and 20th-century London. Rat-proofing the city required meticulous care, perseverance, and work, which gave rise to the Rat Officers. Rat officers were such an integral part of the city that losing them was described as losing “the spirit of the city itself”(Allen, 2009). In addition to rat officers, a national holiday called Rat Week came into existence.

Rat officers were appointed in London from the 1920s until the 1940s. The most famous was Jack Black, who was Queen Victoria’s personal rat catcher. The first duty of the rat officer was to examine ships under Article of 28 of the International Sanitary Convention. The second duty was to visit ships coming from plague infected ports to search for dead rats and if possible, to obtain specimens of live rats. Rat officers were required to re-visit ships daily when cargo was discharged to see if dead rats were found in the holds. The third duty was to examine shore premises for signs of rat infestation or rat plague. Each Rat officers would map out his district in sections and advise warehouse keepers to carry out intensive trapping and to keep all rats until they could be collected each day by the rat-searchers. In this way, the docks were regularly inspected for signs of rat-infestation and plague.

II. Prevention Measures and Methods. Written by Sheyla Nguyen

Rats were especially problematic on ships because of the attractive material in the cargo such as grain, ground nuts, and rice. The existence of this rodent on any vessel had to be detected at the earliest possible moment because if more than two cases of human plague were reported in the Port of London, the port would have to be declared as infected and the financial loss to the shipping trade would be immense. The Port of London authorities were constantly carrying out measures to prevent rats from coming onto shore.

One prevention measure that The Port of London Authority took up was make bye-laws that required the Master of every ship’s product to be overseen by guards. Items such as packages, empty cases, and barrels had to be checked by rat officers to make sure that rats were not contained in them. The mooring ropes also had to be overseen by rat officers because there were fears that rats could use them to reach the shores. A second prevention of rats was the burning of sulfur. Sulfur was burned at the rate of 3 lbs. per 1,000 cubic feet of space (City of London, 1931, MOH). Hydrocyanic Acid Gas was also used but it was not just against rats, it was against bed-bugs and cockroaches. Gases were a very effective prevention measure and were applied to small cargo vessels without risk. A third prevention measure method which was the most important and was constantly used was trapping, to ensure that no rats passed through the ships and onto the shores. All vessels from plague-infested ports were required to have traps set. Trappings were carried out by professional rat-catchers but crew members could also do it, but only under the supervision of the officers of the Port Sanitary Authority. There were various kinds of traps and the best one was the simple “break-back” trap, where a spring would release once the bait was gnawed on, resulting in a dead rat.

Rat proofing methods such as trapping, poisoning, and fumigation were effective but it did not give permanent results as these “frequently leave a few live rats behind from which a new colony rapidly grows (City of London, 1932, MOH).” According to the MOH of the City of London in 1932,

The broad principles of rat-proofing are simple:—
1. Dead spaces in which rats may nest and breed undisturbed must be eliminated,
or, if it is not possible to eliminate them, they must be made inaccessible to rats. In this connection it is important to appreciate how small an opening will admit a rat and how strong are their teeth. Consequently, if openings are not blocked by sheet metal it is necessary to use expanded metal of not more than half-inch mesh.
2. Openings through which rats may pass from one compartment to another must be closed in order to prevent rats from travelling about the ship in search of food and water.
3. Rats do not usually gnaw on flat surfaces, but on edges and angles to which special attention is therefore necessary.

Though these principles are simple and even obvious their application to the
varied conditions in ships requires a knowledge of ship construction, imagination
and an eye for detail. Mr. B. G. Holsendorf. of the United States Public Health Service, is thus equipped and in association with Dr. S. B. Grubbs has compiled a report on “The Rat-Proofing of Vessels,” which contains not only the theory of rat-proofing, but practical instructions for the execution of the work together with a large number of illustrative diagrams and photographs. (City of London 1932)

One reason why trapping was such an important method of rat proofing was because it was necessary to examine the rats in case they were carrying fleas, bringing diseases which could end up killing many individuals. This brings us to the next important job of rat officers, examining the rats.

III. Examination. Written by Courtney Chambers

The examination of rats was an important part of determining if a rat was carrying a disease and the danger that the rats posed to the community. Most of the time the rat officers would spend their days and nights searching for rats in hopes of using them as specimens for testing. The rats seemed to gather in places such as large ports and were frequently found in the Port of London. Wherever frequent shipping was taking place, rats seemed to follow. Examining rats became a main source for information of how to handle and exterminate the different types of rats. There were two main types of rats in London: the black rats (Rattus rattus) and the brown rat (Rattus norvegicus). The black rat was distinguished once turned over onto its head and the tail could reach beyond its head if it is stretched back. Also the black rats have large, thin ears. The brown rat’s tail would reach to about its eyes and the brown rat’s ears were much thicker and they were also considerably smaller than the black rats (City of London 1935, MOH). According to Hannah Velten, black rats were attracted to London because they could eat waste food (p. 216-217). As London’s sewage system was inadequate in the 19th and early 20th centuries, waste was fairly frequent through drains and the streets. The Rat Officers’ duty of examination was crucial for the other duties that the officers had. Examination of rats gave the officers and health officials an insight into what kind of rats they were dealing with and if the rats carried any diseases that posed a risk to the citizens.

Once the rats were dead from the extermination duties or caught, they were sent to the Central Health Laboratory in Colindale for bacteriological examination (City of London 1957, MOH). Rats were particularly tested for bacillus yersinia pestis, as well as examined for any fleas or lesions they may have had. Yersinia pestis is a species of bacteria that is transmitted from rat to rat and from rat to human. The bacteria can cause the plague in humans, rats and various other mammals. The disease is hosted by fleas, up to as many of 30 species of fleas (Hillary Hurd). In the time of the plague, Velten mentioned in her book that particularly the black rat’s fleas were the cause of the devastation. The most popular flea, that also was a large contributor to the cause of diseases, including the infamous plague but not limited to, was the rat flea Xenopsylla (Hillary Hurd). These fleas would live on the rats. As the rats invaded areas of civilization the fleas would then transmit bacteria to the humans and animals such as cats, dogs. The plague was indirectly caused by rats because of the fleas they carried. The average ratio of fleas per rat was 3:08. In the year of 1932 the species C. fasciatus was the most predominately known flea of this time(City of London 1932, MOH). Of the rats examined, for this time period, 89.3% of the fleas were of this species. Interestingly, the species of fleas also changed depending on the season or the type of weather. During the colder months it was more common to find the species of flea called the Leptopsylla musculi (City of London 1932, MOH). The most amount of fleas ever recorded on a single rat was 61. The type of rat that possessed this large amount of fleas was a brown rat. This rat was trapped at Tilbury Dock in November 1932. Each of the 61 fleas were recorded as the species of C. fasciatus (City of London 1932, MOH). 10% of the rats examined in 1932 in the City of London were found to have microscopical lesions indicating that these particular rats were a plague-carrying rats.

The Rat Officers’ duty to examine rats was critical as it provided information about diseases the rats were carrying. Once they examined the rats they had caught, the officers could begin forming plans about how to contain the rats in a specific way that would not harm the citizens.

IV. Rat Killing. Written by Rida Raza

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Her majesty’s personal rat catcher Jack Black. Mayhew, H. (1851). “London Labour and the London poor,” Volume 3, pg. 11, Wikipedia.

Rat officers were tasked to differentiate between the black and brown rat before carrying out their extermination duties. As stated previously, the black rats had long tails with large, thin ears while the brown rats had thick, small ears and a shorter tail. Rat droppings also served to help the officers identify the rat species. The rat officers employed varying methods of “de-ratization” depending on the type of rat they identified. Black rats were the primary culprit in London (261 infestations as opposed to 23) and they usually infested city buildings. Due to their proximity to humans, poisons were rarely used. Rat officers had trouble targeting the pesky black rats because the Rats and Mice (Destruction) Act made disinfecting the duty of building owners.

After trapping, the most commonly used de-ratization technique in the 1930s was fumigation. In the event of, or suspicion of, rodent plague on a ship, fumigation with HCN was done promptly. Infected ships were fumigated before they were emptied. This shows how much of a nuisance the rats had been to Londoners. The London population desperately wanted to get rid of the rats so they were willing to have the ships disinfected prior being unloaded. After the ships were emptied, a second round of fumigation with HCN occurred. Rats and fleas on the ships were killed to lessen spread of the disease to shore rats. At higher concentrations, 12 to 24 hours of HCN exposure could kill many other insects like bed-bugs and cockroaches. Many of the infected ships exterminated rats by using sulphur dioxide and some ships were fumigated with a combination of HCN and SO2. Eventually, ship owners realized that if they set up traps themselves they could avoid having to wait while their ship gets fumigated.

It was vital for fumigators to be knowledgeable, organized, and disciplined or else fumigation would be unsuccessful. In the hands of an inexperienced fumigator, HCN could be deadly not only to the fumigators themselves, but also to the people that benefit from the fumigations. It was imperative that Port Medical Officers of Health certified the skills of the fumigators and supervised fumigations in their respective districts. Also, the Medical Officers of Health educated the fumigation team about the dangers of HCN and trained them to take the necessary safety precautions.

Rats were killed incessantly because they were a vessel for the plague. The photo at the top of the page shows rat dipping which was a technique for disinfecting rats. It was most commonly used to kill fleas on the rats. Initially, assistant rat officers tried to dip the rats by themselves in a flea-killing solution. This method was found to be ineffective so instead they placed the rats in bags. The rat bags were then dipped into kerosene to destroy the fleas that may have been carrying the plague. Methyl Bromide was another fumigant that was used to kill insects on the rats. It was mainly used when rats and insects were infecting the same area.

Rat officers were not the only group of people that engaged in rat killing. Hannah Velten wrote about how rat killing was turned into a sport by the people of London in her book Beastly London: A History of Animals in the City. People would bring their dogs to public houses known for sporting contests and have them fight and kill the rats (108). Many people would come to watch these weekly fights and the rat killings were even advertised in the newspapers.  Some of the dogs behaved cowardly towards the rats while others successfully killed many rats. The most accomplished rat killer was a dog named Billy that managed to kill over 4,000 rats. The rat baiting was eventually shut down by the Royal Society for the Prevention of Cruelty to Animals.

Sanitation was a huge issue in London, especially in the slums. The people in the slums were affected by over-crowding and starvation. The risk of diseases spreading is dangerously increased in areas where over-crowding is a problem. Rats are often present in unsanitary locations so the slums were a breeding ground for plague and disease infected rats. The general public turned their attention to helping these areas so that the plague and various other diseases could be eradicated.

New poisons were created as time progressed into the 1940s and 1950s. The poisons replaced trapping as the primary method of de-ratization in London. In addition, fumigation became an invalid rat killing method as it was no longer used by many countries. The two rodenticides utilized were 1080 and Warfarin. Both poisons produced sufficient positive results ashore but the use on ships was still under experimentation. Another experiment was conducted to see if the rats would consume a grain that was mixed with the rodenticide Warfarin; however, the results were not reported in the 1951 MOH report. Rat poisons were preferred to fumigation because they were more cost efficient for the ship owner and less time consuming to implement.

The job of rat officers was incredibly important to the city of London in the early 1900s. Rat officers had the liberty to test out different methods to see which ones were effective. Scientists created new methods and techniques for them to try.  Rats were a nuisance and spread disease through the fleas on their bodies. Without rat officers, many more people would have been infected and could have died from the diseases that rats carried.


Sheyla Nguyen

  1. City of London, 1913, MOH
  2. City of London, 1919, MOH
  3. City of London, 1920, MOH
  4. City of London, 1924, MOH
  5. City of London, 1929, MOH
  6. City of London, 1931, MOH
  7. City of London, 1932, MOH
  8. City of London, 1933, MOH
  9. City of London, 1935, MOH
  10. City of London, 1937, MOH
  11. Allen, Michelle. Mayhew on Toshers, Cesspool-sewermen, and Rat Catchers. The Victorian Web, 2009. (accessed April 06, 2017).
  12. Velton, Hannah. Beastly London: A History of Animals in the City. Reaktion Books, 2013.
  13. Walter, Luke. The Rats of London. Victorian Gothic, 2011. (accessed April 6, 2017)

Courtney Chambers

  1. City of London 1911, MOH
  2. City of London 1916, MOH
  3. City of London 1919, MOH
  4. City of London 1921, MOH
  5. City of London 1931, MOH
  6. City of London 1932, MOH
  7. City of London 1935, MOH
  8. City of London 1937, MOH
  9. City of London 1951, MOH
  10. City of London 1957, MOH
  11. City of London 1964, MOH
  12. Velten, Hannah. Beastly London: a history of animals in the city. London: Reaktion Books, 2013.
  13. Warren, Andrew Scott. Examination of Black Death and Public Health Implications for Today. Master’s thesis, University of Connecticut Digital Commons , 2001. 1-81.
  14. 2015, Hilary Hurd 16 Mar. “Rats are exonerated as reservoir hosts for the Black Death.” BugBitten. March 26, 2015. Accessed April 06, 2017.

Rida Raza

  1. City of London 1930, MOH
  2.  City of London 1931, MOH
  3. City of London 1932, MOH
  4. City of London 1935, MOH  
  5. City of London 1937, MOH
  6. City of London 1939, MOH
  7. City of London 1940, MOH
  8. City of London 1947, MOH
  9. City of London 1951, MOH
  10. City of London 1967, MOH
  11. Diniejko, Andrzej. Jack London’s Autobiographical Account of the East End Slums: The People of the Abyss. The Victorian Web, 2011.
  12. Rees, Luke. Blood, Betting and Baiting: The Dark History of London’s Pubs. The Victorian Web, 2014.
  13. Velten, Hannah.Beastly London: A History of Animals in the City. Reaktion Books, 2013.