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The Gilded Vectors of Disease: Sculptures at the London School of Hygiene & Tropical Medicine

Decorating the exterior of the London School of Hygiene & Tropical Medicine (LSHTM) is a frieze in the Art Deco style of gilded bronze figures of ten different animals. The figures are sculpted into the iron balconies on the first floor overlooking the front and sides of the building. All the animals represented can affect human health and well-being adversely. Most live in close proximity to man. Man provides the food and shelter these animals require to facilitate rapid population growth until they become pests.

Eight of the animals are arthropods and of these seven are insects – the flea, the tsetse-fly, the housefly, the bedbug, two types of mosquito, and the body louse – plus the tick which is an arachnid. One mammal is represented – the rat, and the reptiles are represented by a snake.  The actual selection process that led to the particular choice of animals in the frieze is unknown. Eight are vectors that can transmit dangerous parasitic microorganisms to man causing diseases:  at the School the sculptures of these eight are referred to as ‘the gilded vectors of disease’ (neither the snake is a vector nor, we now know, is the bedbug).

London School of Hygiene & Tropical Medicine, Keppel Street building from Malet Street

The purpose-built building in Keppel Street, Bloomsbury, was opened by HRH the Prince of Wales on 18 July 1929. Now Grade II listed (9 March, 1982), it is a steel-framed building with a Portland stone façade, designed in the stripped Classical style by the architectural partnership of Verner Owen Rees (1887-1966) and Percy Richard Morley Horder (1870-1944).  The firm of J. Starkie Gardner Ltd., Decorative Metal Workers, of Southfields, made the iron balconies. The sculptures, which measure approximately 26 cm. high x 27 cm. wide (maximum) are sculpted into a pattern of grey iron squares measuring 28 cm. high x 27 cm. wide (outer edge). In total there are 30 sculptures arranged in pairs, each of the 10 figures repeated three times in different pairings.  In life the insects and the tick measure less than 1 centimetre long. Here, for the sculptures, they have been greatly enlarged.  In contrast, the cobra snake figure has been scaled down from the size of an adult, and the rat sculpture is approximately life-size.  All the animal figures are somewhat stylized although most retain the essential characters for scientific identification to genus level.  Responsibility for the frieze design is attributed to architect P.R.Morley Horder1.

Species of all the animals on the frieze live in the UK except for the tsetse-fly which is endemic in Africa and the Middle East and the particular snake represented – the cobra – which is found on the Indian subcontinent and in Africa. During World War I (1914-18) it was discovered that many soldier’s deaths arose not just from the actual conflict but from diseases contracted in the trenches and camps, spread by some of these animals. In Britain there were official campaigns to educate the public about the dangers these pests posed.  The Natural History Museum in South Kensington printed eye-catching posters about three of them to aid identification and recommend methods for their destruction2.  Despite the precautions, and the efforts by governments and pest controllers, 100 years on, all these animals are still with us and still present a threat to human health, their distribution and populations rising and falling, as environmental conditions and other factors change.

Insects comprise about half of all known living animals and display an unparalleled range of colours, shapes, sizes, and beauty. They can live anywhere in the world except the polar regions, yet, unlike some other animals, they have rarely been used in the decoration of public buildings (Ruthven 2011: 112-113, 118-119, back cover).  Even the Natural History Museum, covered internally and externally with terracotta figures of fauna and flora, has few insects in the ornamentation. The presence of these arthropod figures on the LSHTM is unique in London for both variety and quantity displayed on one building: it prompted a remark at the time of the building’s opening that it must be “the first official appearance of the louse as a decorative emblem”3.

The following illustrated descriptions outline briefly the ten animals depicted – their life cycles and medical importance.

Vector Natural history Medical importance
THE BODY LOUSE

Classification
Phylum: Arthropoda
Class: Insecta
Order: Phthiraptera
Family: Pediculidae
Genus: Pediculus
Species: Pediculus humanus, Body Louse.

The body louse is a small (2-4 mm long), oval-shaped insect, greyish in colour. It has 6 legs that end in claws by which it attaches itself to clothing and occasionally bedding. Body lice are cosmopolitan and associated with overcrowded and unsanitary living conditions. Both sexes feed on blood and have mouthparts designed for piercing skin and sucking blood. The life cycle involves three stages before an adult emerges. These insects are wingless and spread by direct contact with infected people, contaminated towels, etc. Body lice are vectors of louse-borne typhus, trench fever and louse-borne relapsing fever. Infection is caught when a louse that is sucking up blood passes infected faeces on the skin. Cutting through the skin causes irritation. The person responds by rubbing the affected spot and, unwittingly, forces the infected faeces into the wound, and ultimately into the blood.

Head lice, Pediculus capitis, are indistinguishable to the naked eye from body lice. They live on the hairs of the head. Although they do not transmit any pathogenic organisms, their bites cause irritation. ‘Nits’ that fall out during combing are usually empty white egg cases.

THE BEDBUG

Classification
Phylum: Arthropoda
Class: Insecta
Order: Hemiptera
Family: Cimicidae
Genus: Cimex
Species: Two species of the bedbug Cimex affect humans: Cimex lectularius, the common bedbug, found in all regions of the world; C. hemipterus, the tropical bedbug, mostly occurs in the tropics. The two species are very similar in appearance.

Bedbugs are small (5-7 mm long), flattened, oval-shaped insects, pale-brown in colour except after taking a blood meal when they turn chestnut brown. Both sexes feed exclusively on blood using mouthparts adapted for piercing through skin and sucking up blood. Bedbugs live in houses, hiding in dark recesses and crevices in wooden beds, mattresses, by day and crawling out at night to feed on sleeping people. The life cycle, which involves many development stages before an adult emerges, occurs in places where the bugs live. Bedbugs are wingless, and unable to fly: they are dispersed by movement of second-hand goods infested with them, such as furniture, mattresses, and by suitcases. Bedbugs saw through skin using their sharp mouthparts and cause irritation and itching; some people may suffer severe reactions. At the time the School was built it was thought bedbugs were vectors but it has since been found out that they are not.
THE TSETSE-FLY

Classification
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Glossinidae
Genus: Glossina
Species: There are 23 species of the tsetse-fly, Glossina. Tsetse-flies are vectors of human and animal trypanosomiasis. Species causing sleeping sickness include Glossina morsitans and G. palpalis.

Tsetse-flies are large (6-14 mm long), brown-black biting-flies with six legs. Both male and female tsetse-flies feed on blood using mouthparts adapted to pierce through skin. Their distinguishing features are a proboscis (a needle-like structure projecting forward from the head used to suck-up blood), and one pair of wings which, when at rest, fold over the body (NB LSHTM sculpture shows the wings spread apart). Most tsetse-flies live on vegetation in tropical Africa south of the Sahara. They feed exclusively on mammals that they locate by sight and smell with their large eyes and antennae. The life-cycle is unusual in that it produces live young, one at a time, followed by a pupal stage, before an adult emerges and flies away. Tsetse-flies are vectors of a microscopic protozoan parasite, Trypanosoma, that causes human trypanosomiasis or sleeping sickness. Infected tsetse-flies inject the parasite into the blood during feeding.
THE TICK

Classification
Phylum: Arthropoda
Class: Arachnida
Subclass: Acari
Order: Ixodida
Family: Ixodidae (hard ticks)
The family Ixodidae has 12 genera, 713 species. Medically, one of the most important genera is Ixodes, of which there are several species. The tick on the frieze is an example of a hard tick but its identity has not been determined.

These notes refer to the tick genus Ixodes. Ixodes is a hard, small 2-4 mm long arachnid. The body is flattened and it has mouthparts adapted for cutting through skin to reach the blood vessels. It has four pairs of legs and its colour may be greyish to red-brown. Ixodes has a worldwide distribution. People pick up ticks accidentally when passing through an area with a reservoir of wild animals infested with them. Once on the body, they insert their mouthparts into the skin and cement them in place to enable continuous blood feeding for long periods. Ixodid ticks lay 1000s of eggs that undergo a complex, three-stage life-cycle before emerging as adults. Ixodes ticks cause discomfort and irritation by their bites. They may also carry infective pathogens that they transmit to humans through their bite including borrelia that is the cause of Lyme disease. Other tick species can transmit harmful pathogens that cause human diseases.
THE HOUSEFLY

Classification
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Muscidae
Genus: Musca
Musca has 70 species, of which the most common is Musca domestica, the housefly.

Houseflies are 6-9 mm long insects, light to dark-grey in colour. When at rest the single pair of wings folds over partially covering the body. Each of the three pairs of legs ends in a sticky pad that enables the fly to adhere to smooth surfaces such as windowpanes and ceilings. Houseflies are ubiquitous: they have the widest distribution worldwide of any insect and live in close association with humans. They can feed only on semi-liquid foods that they suck up through specially adapted mouthparts. This may be food intended for humans as well as kitchen waste, carcasses, faeces. Their life cycle involves several intermediate stages, of which the maggot stage often found in decomposing food is the one most likely to be encountered, before the young adult emerges and flies away. Flies present a nuisance when in the proximity of food but they are difficult to catch due to large and highly efficient eyes alerting them to imminent danger, enabling them to make a quick getaway. Houseflies have habits that have hygienic implications as well as being mechanical vectors, picking up harmful organisms (bacteria, viruses, protozoans, helminth eggs), on their bodies during feeding and depositing them on food prepared for human consumption. Vomiting and diarrhoea after eating are often caused by consuming food that has been contaminated by flies.
THE FLEA

Classification
Phylum: Arthropoda
Class: Insecta
Order: Siphonaptera
220 genera, 2200 species and subspecies, eg Human flea Pulex irritans; an important species is the rat flea, Xenopsylla cheopis, a vector of the bacterium causing bubonic plague, and flea-borne murine typhus.

Fleas are hard, small (1-6 mm long), oval insects, with narrow bodies and brown in colour. Fleas occur worldwide. 94% of all flea species live on the hairs of mammals. The other 6% live on birds between feathers. Only a few flea species affect humans where they are usually associated with bedding and clothing. All fleas are blood-suckers using their sharp mouthparts to cut through skin to reach blood vessels. The life cycle involves several development stages in the habitation of the host before a young flea emerges. They have no wings so cannot fly away but have three pairs of powerful legs enabling them to jump great distances to find a suitable host. In humans, fleas mainly cause discomfort and irritation arising from their bites, and are swift-moving and difficult to catch, eg the human flea, Pulex irritans. However, some fleas are vectors of dangerous viral and bacterial pathogens such as those that cause bubonic plague and flea-borne murine typhus which are spread in the bite of an infected rat flea Xenopsylla cheopis. The rat flea, carried on rats, caused the deaths of thousands of people during the Great Plague of London in the 17th century.
THE MOSQUITO, Anopheles

Classification
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family Culicidae
Subfamily: Anophelinae
3 genera, c490 species.
In this subfamily only genus Anopheles is medically important in the spread of malaria. Anopheles gambiae, found in Africa, is one of the most dangerous species.

Mosquitoes are small (3-6 mm long), slender insects with elongated mouthparts and conspicuous eyes. They have a single pair of long, narrow wings and three pairs of long, slender legs. Male and female mosquitoes feed on sugar but it is only the females that are blood-suckers and of medical importance. Mosquitoes are cosmopolitan and must have access to still water for successful completion of their multi-stage development cycle to adults. The unmistakable loud whine of female mosquitoes is the first sign of their presence usually in the early morning or evening when they are active. They move fast, detecting imminent danger with their eyes and other sense organs. Unlike other mosquitoes Anopheles rest with their bodies pointing up in the air at a 45 degree angle, as shown in the sculpture. When biting, infective female mosquitoes of the genus Anopheles transmit the microscopic protozoan parasite Plasmodium into the blood that causes malaria. Malaria is a disease affecting millions of people living in tropical and subtropical regions in Africa, Asia and Latin America. Every year malaria causes thousands of human deaths. Some Anopheles species are vectors of filariasis.
THE MOSQUITO, Culex, Aedes

Classification
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family Culicidae
Subfamily Culicinae
38 genera, 2750 species. In this subfamily of Culcine mosquitoes the most important vectors are species of the Aedes and Culex genera.

Mosquitoes are small (3-6 mm long), slender insects with elongated mouthparts and a pair of conspicuous eyes. They have a single pair of long, narrow wings and three pairs of long, slender legs. Only female mosquitoes of some species are blood-feeders and of medical importance, using sharp mouthparts to cut through skin. Most other mosquitoes that cause a nuisance by their biting (but are not medically important vectors as Aedes and Culex are) belong to the Culicinae subfamily, and live in northern Europe, Asia and America. The presence of freshwater in which the females lay their eggs is essential for the successful completion of the multi-stage development cycle before the adults emerge. The loud whining noise females emit is the most obvious clue to their presence but their eyes and other sense organs detect imminent danger and enable them to move quickly out of harm’s way. Most culicine mosquitoes at rest hold their bodies parallel to the surface on which they have alighted, as shown in this figure. Of the Culcine mosquitoes the most important vectors are the genera Aedes and Culex. Aedes transmit arboviruses including dengue, zika, yellow fever and chikungunya. Culex transmit west nile, jap B encephalitis and filariasis.
THE RAT

Classification
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Murinae, rats and mice
Genus: Rattus
Rattus rattus, the Black Rat or roof rat; Rattus norvegicus, the Common or Brown Rat.

Two species of rat had adverse effects on humans in Western Europe: the Black Rat, Rattus rattus and the slightly larger Brown or Common Rat, Rattus norvegicus. Rats are small mammals. Brown rat, head and body (HB) measures 160-290 mm, tail length (TL) c80-97% of HB; Black rat, HB measures 116-260 mm, TL c95-120% of HB. Rats are usually found in close proximity to human habitations. By day they hide and at night venture out to find food: with their ever-growing front teeth they can gnaw into the hardest materials. Rats have a tremendous capacity to multiply. On reaching maturity at about four months, after a short gestation of about 22 days, a female produces a litter of 3-7 or 8 helpless, blind young in a nest she has constructed. Females may have up to five litters a year, and in females living in a group there may be synchrony so that large numbers of young are born within a short period, increasing the survivability rate, hence the build-up of large populations. In Europe from the Middle Ages, when rats from Asia were first introduced they were a pest: they destroyed grain, contaminated food and damaged property, and carried fleas and parasites that led to terrible outbreaks of plague and other diseases. Today they continue to be important pests. The rat flea, Xenosylla cheopsis, living on the rat and carrying the plague bacillus can leap on to people and infect them when it takes blood. Weil’s disease is caught by people whose work brings them into close contact with rats, eg farmers, fishermen, sewer workers. It is caused when bacilli present in the rat are passed out in urine, and accidentally enter the body through scratches or cuts.
THE SNAKE

Classification
Phylum: Chordata
Class: Reptilia
Order: Squamata
Sub-order Serpentes
Family: Elapidae
Genus: Naja
Naja naja is the Indian cobra.

The snake in the frieze depicts the cobra, Naja, a venomous snake found on the Indian subcontinent and in Africa. When threatened it raises its head and erects a large hood around the head (as seen in the sculpture). Adult cobras are 1-1.5 metres long. They live in a wide range of habitats – forests, rice fields, and villages. The females lay eggs in rat holes. When the young snakes hatch, they are immediately ready for an independent existence. Cobras eat frogs, rats, and small birds. The cobra is a highly dangerous snake. Its venom is fatal unless treated rapidly and it is responsible for many deaths every year in India. In India cobras also serve as important natural predators by keeping down the rat population responsible for contamination and destruction of grain stores. Snakes have great socio-economic importance in India and Africa. Since ancient times, humans have had a love-hate relationship with the snake, from its appearance in the Garden of Eden and as an object of fear and revulsion. In medical and pharmacological iconography, snakes are frequently included in official corporate images including the World Health Organisation (WHO).

 

DEFINITIONS

Arboviruses. Arthropod-borne viruses. A virus that multiplies in an arthropod and is transmitted by its bite to a vertebrate host (Service 2012: 279)

Vector. A vector is an animal, usually an insect or a tick, that transmits parasitic organisms – and therefore the diseases they cause – from person to person or from infected animal to human beings. Mosquitoes, for example, are vectors of malaria, filariasis and yellow fever. (Concise colour medical dictionary. 3rd ed. (Oxford: Oxford University Press) 2002.

ACKNOWLEDGEMENTS

With thanks to staff at LSHTM: in the Library & Archives team: Claire Frankland, Aisling O’Malley, Manasseh Boyd; Eloise Carpenter; Gemma Bayliss; Professor James Logan, LSHTM Head of the Department of Disease Control and Director of ARCTEC; Paula Jenkins, Natural History Museum; Barry Hughes.

NOTES

  1. Percy Richard Morley Horder. https://en.wikipedia.org/wiki/Percy_Richard_Morley_Horder (viewed 4/4/2019). Despite an extensive search of the School Archives it has not been possible to confirm the identity of the designer of the sculptures.
  2. The Natural History Museum (then known as the British Museum (Natural History)) posters were issued in 1918, and 20,000 copies of each were printed, sold at one halfpenny each. One was on the fly. http://collection.sciencemuseum.org.uk/objects/co8093151/the-fly-danger-poster-united-kingdom-1918-poster (viewed 30/4/2019). The Museum put on an exhibition of wax models of arthropods of medical importance in 1916 and published an accompanying illustrated catalogue: Guide to the specimens and enlarged models of insects and ticks exhibited in the Central Hall illustrating their importance in the spread of disease (London, 1916; Special guide No. 7). A second edition was published in 1919.   The exhibition was on public display at least until the mid-1920s.
  3. Quoted in G.C. COOK (1992) From the Greenwich hulks to Old St Pancras. A history of tropical disease in London (London: The Athlone Press), pp. 249-250; from: ANONYMOUS (1929) ‘Preventive medicine in London: the new School of Hygiene and Tropical Medicine’, Lancet 1929 ; ii : 148-150.

 

REFERENCES AND FURTHER READING

BARNETT, S. Anthony (2001) The story of rats. Their impact on us and our impact on them (Crows Nest, NSW, Australia: Allen & Unwin) Pp.xiii, 202.

BURGESS, N.R.H.  (1990) Public health pests. A guide to identification, biology and control (London: Chapman and Hall) Pp. xi, 162.

BURGIN, C.J. (2017) Species accounts of Muridae. Pp. 829-831 in: WILSON, D.E., LACHER, T.E., Jr. and Mittermeier, R.A. (eds) Handbook of the mammals of the world. Vol. 7. Rodents II (Barcelona: Lynx Edicions)

HINTON, M.A.C. (1931) Rats and mice as enemies of mankind. 3rd ed (London: British Museum (Natural History)) Pp. x, 70.  https://www.biodiversitylibrary.org/bibliography/86373#/summary (viewed 1/5/2019)

MORRIS, Ramona & MORRIS, Desmond (1965) Men and snakes (London: Hutchinson) Pp. 224.

REES, Verner O. & HORDER, P. Morley, 1929. London School of Tropical Medicine, The Architects’ Journal 70 (No. 1800): 84-89.

RUTHVEN, Ianthe, 2011. Animal London: a spotter’s guide. (London: Square Peg).  Pp. 172.

SERVICE, Mike (2012) Medical entomology for students. 5th edition (Cambridge: Cambridge University Press). Pp. xx, 303.

WILKINSON, L. & HARDY, A. (2001) Prevention and cure. The London School of Hygiene and Tropical Medicine. A 20th century quest for global public health (London, &c: Kegan Paul). Pp. [6], 438.

THE GILDED VECTORS OF DISEASE. Wonders of science! Bizarre histories! Real & true facts! Amazing creatures. (2013). Produced by Rebecca Tremain & Rob Falconer. (The Mustard Club in association with London School of Hygiene & Tropical Medicine). Original series first broadcast on Resonance FM Radio 4 April to 23 May 2012.  Two disc Collector’s Edition. Highlights from the Radio Series.

 

IMAGES

© LSHTM ‘Keppel Street building from Malet Street’

© User:Colin / Wikimedia Commons CC BY-SA 4.0 https://commons.wikimedia.org/wiki/File:Gilded_Vectors_of_Disease_-_Horizontal.jpg

 

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