The Cambridge Group for the History of Population and Social StructureMathias Mølbak Ingholt
Many people know that malaria is a mosquito-borne disease that largely occurs in tropical regions. However, it is not so well known that malaria was endemic in parts of northern Europe – including Britain – until relatively recently.
Unlike Plasmodium falciparum malaria, which today dominates in Sub-Saharan Africa with high mortality rates, European malaria was caused by Plasmodium vivax, a species with low mortality. It was eradicated from Europe only relatively recently, in the 20th century – yet surprisingly little is known about its history, and there is still some debate about how important a disease it was in the past.
Malaria, agues, and fevers
The word “malaria” comes from the Italian words mal and aria, meaning “bad air”. This was a reference to the miasma theory of disease, according to which disease is caused by exposure to unhealthy vapours that emerged spontaneously. These vapours were believed to have existed in marshes and wetlands, and these ecotypes were stigmatized as very unhealthy in 17th-19th century literature. In the case of Britain, wetlands were associated with “agues” and “marsh fevers”, and in Denmark and Germany, wetlands were associated with “koldfeber” (cold fever) and “fevers” in general.
Frederick Milner, Marshland. Harris Museum & Art Gallery.
When Daniel Defoe visited the Thames estuary in 1721, he described how the marsh farmers married women from the uplands. After a short residence in the marshes, the women died from “agues”, and the men would then remarry. Defoe concluded that the men, having lived in the marshes since childhood, were grown accustomed to the “bad air”, whereas the women they married, who were not used to marsh conditions, were affected much harder.
Historians have often assumed that the agues and marsh fevers described by Defoe and others were synonyms for modern malaria. From an academic perspective, however, this assumption is problematic, because the meaning of the words used to describe these diseases has changed over time. According to the medical historian Christopher Hamlin, “ague” originally referred to any acute fevers, and hence not necessarily to malaria, and the modern tendency to conflate fevers, agues and malaria has potentially led to anachronisms.
Fever, represented as a frenzied beast, stands racked in the centre of a room, while a blue monster, representing ague, ensnares his victim by the fireside; a doctor writes prescriptions to the right. Etching by T. Rowlandson after J. Dunthorne, 1788. Wellcome Collection.
The demographic impact of malaria
Despite confusions of terminology, however, the connection between marshes and modern malaria is not unreasonable. When medical statistics in Denmark were first aggregated in the second half of the 19th century, the largest malaria burden was on the flat and clayish islands of Lolland and Falster, which had had a reputation for ill health and “fevers” in earlier centuries.
In England, too, living in the marshes had multiple demographic disadvantages. Infant mortality rates in marsh parishes were higher than in upland parishes. In Kent and Essex, more people were being buried than baptised in the marsh parishes throughout the 17th and 18th centuries, suggesting that death rates here were very high.
E. P. Lilley, Marshland. Hastings Museum and Art Gallery.
The historian Mary Dobson has argued that malaria was a more lethal disease in this period, only becoming milder in the 19th century, due to a combination of improved drainage, a changing virulence in the parasite, and more tolerance in the population. Evidence from late 19th century Denmark does indeed point to a low case fatality ratio of 0.17 percent (that is, 25 deaths per 15,000 cases of malaria), indicating that it was not in fact an acute cause of death by this point.
Others have argued that although malaria itself may not have been an acute cause of death, the constant exposure to malaria in marsh parishes rendered those populations more vulnerable to other infections, explaining the high mortality rates. High neonatal infant mortality rates may have been due to mothers being unable to breastfeed during frequent fever bouts, and to the practice of giving infants opium, which was widely used and abused as a treatment for malaria. Finally, some have emphasized the role of poor water quality in the marshes, arguing that diarrhoeal diseases played a major part in the high mortality rates.
Why did malaria disappear?
The disappearance of malaria in Europe has been explained by changes in the human exploitation of natural resources. One frequently cited hypothesis is that malaria disappeared because of agricultural improvements in the 19th century. Before then, the physical landscape was very different from that of today. The soil was wetter, forests were more widespread, and creeks and rivers had large deltas with flood plains. Advances in drainage techniques and steam-driven pumps meant that venture capitalists and farmers were able to drain their fields more efficiently, embank wetlands and turn them into arable farmland, and dry out bogs. The consequence was that the parts of Britain and Denmark that were previously wetland are today the most productive arable farmland.
But this agricultural revolution also had other unintended consequences. Clifford Darby has argued that the draining of the Fens led to an ecological collapse with many species of insects and birds disappearing.
These land improvements would have had the consequence that mosquito populations were considerably reduced in the low-lying areas, and thereby the risk of humans contracting malaria was considerably reduced too. This in turn would have lowered the risk of mortality from other causes, assuming that chronic malarial infection constituted a significant co-morbidity.
John Sell Cotman, Drainage Mills in the Fens, Croyland, Lincolnshire. Yale Center for British Art.
Improvements in housing that reduced exposure to mosquitoes has also been suggested as a reason for the decline of malaria and, finally, it has been suggested that expansions in livestock herds meant that mosquitoes became naturally attracted to livestock and hence lost their preference for human blood. Since the malaria parasites cannot survive in livestock, this would have ended the transmission of the disease.
In Denmark, malaria incidence rates plummeted during the 1870s and 1880s, and by the turn of the 20th century, nearly all Danish cases were imported. The case of Britain was similar; after the First World War, returning soldiers stationed on the Isle of Sheppey infected with malaria managed to start a small epidemic, showing that malaria still had the ability to thrive in northern Europe.
Disentangling the local effects of malaria as a co-morbidity from the overall great decline is difficult to conduct, if not impossible. Nevertheless, what is clear, is that the marshlands went from being the unhealthiest places to live to having the most productive and arable soil, and free of malaria.
Further reading
- Davenport, R., and Satchell, M., ‘Malaria, migration and merry widowers in the Essex marshes 1690-1730’, Local Population Studies 112 (2024), 10-35.
- Dobson, M., Contours of Death and Disease in Early Modern Britain (Cambridge, 1997).
- Ingholt, M. M., ‘An ordinary malaria? Intermittent fever in Denmark 1826-1886’ Medical History 67:1 (2023), 57-73.
- Ingholt, M. M., Chen, T. T., Hildebrandt, F., Pedersen, R. K., and Simonsen, L., ‘Temperate climate malaria in nineteenth-century Denmark’, BMC Infectious Diseases 22:432 (2022), 1-11.
- https://www.campop.geog.cam.ac.uk/research/projects/malaria/
