Linnaeus’ thesis on the ague (malaria)

Malaria mosquitoes thrived in the areas around
Fyris River in Uppsala in the 18th century.
Photo: Uppsala University Library.

The ague was a common disease in Sweden during the 18th century. The disease was also called the ”Uppsala fever”. Linnaeus wrote about the ague: ”In Uppland no disease is more domestic and there it seems to particularly have ingratiated itself. Almost all students in Uppsala are affected by it.” No one knew for sure what caused the disease. It was believed that getting cold or different types of food could give rise to the ague.

In 1735 Linnaeus defended his theses on the ague and presented a new theory of the reason for the disease. The ague seemed to be most common in areas with clay soils. Linnaeus therefore assumed that there were clay particles in the drinking water, and that this might be the cause for the ague. The particles would stick inside the blood vessels, and the body tried to get rid of them with high fevers and heavy perspirations. Linnaeus suggested a medicine making the patient sweat more (a sudorific) as treatment to help the body in its work.

Today we know that Linnaeus was wrong and that the ague is a type of malaria. With the help of a microscope malaria parasites have been discovered. These parasites are transferred to humans by malaria mosquitoes. Since Linnaeus did not have a good enough microscope he could not find the malaria parasites and the true explanation to what caused the ague. Despite the fact that his theories of what caused malaria were wrong, he was near the solution. Malaria is in a way tied to water since the larvae of the malaria mosquitoes live in stagnant water. In the 18th century the mosquito larvae were probably very common in the wet parts of the clay soils around Uppsala.

How the ague disappeared

A blood filled female of the malaria
mosquito Anopheles messae 
photographed in a stable outside Uppsala.
Photo: Thomas G. T. Jaenson.

Malaria was a widespread disease in Sweden until the 18th and 19th centuries. It was spread by malaria mosquitoes,Anopheles, a genus containing the 45 species of biting mosquitoes in Sweden. In those times people had no separate buildings for the cows to live in during the winters. People and cattle lived under the same roof. It was dark and damp and provided a nice environment for the mosquitoes to spend the winter, and the malaria was spread.

Today there are still malaria mosquitoes in Sweden, but the disease disappeared from our country in the beginning of the 20th century. How come that it disappeared?

There are several reasons for the decrease of malaria. The most important reason was that people built better houses and started using separate buildings for the cattle to live in. The mosquitoes liked it better together with the cattle where it was dark and damp than in the drier houses where the people lived. Since the malaria parasite could only survive in human blood, the disease decreased radically.

The malaria parasite decreased in number even more during the cold summers in the 1860's, and further the malaria mosquitoes decreased in numbers when the wetlands where the larvae lived were drained. At the same time people started eating malaria medicine and that was the end of it.

Last modified: 2021-11-25