Originally published here: https://mcgill.ca/oss/article/did-you-know-history/did-you-know-colonialism-responsible-spread-malaria
Malaria is an infectious disease caused by a single-celled parasite that multiplies in human red blood cells as well as in the intestines of the Anopheles mosquito, the insect that transmits the disease. Researchers believe that malaria coevolved with humans in Africa. For its spread across the world, we can blame colonialism.
It is thought that malaria began to travel out of Africa about 3 000 years ago, after which its spread was hastened by wars and the import of human labour. Sardinia is an island south of Italy that was conquered by Carthage in 502 BCE. Seeking to use the land for agriculture, the Carthaginians clear cut the trees and vegetation. These ecological changes allowed flooding to occur, creating standing water that attracted mosquitoes. To work the new farms, Carthage imported labourers from Northern Africa who brought malaria with them.
About 200 years later, the Roman empire took over Sardinia, allowing malaria to make the leap to Europe. By the 1400s, malaria was well established in France and England. As populations grew, agricultural demands led to low lands and swamps being drained, often poorly, and what happened in Sardinia was repeated.
Once colonies in North America and the Caribbean were established, many of Europe’s poor emigrated there, bringing malaria with them. The agricultural practices used in the U.S. to grow cotton and rice, combined with the overcrowding and horrid conditions that slaves faced resulted in epidemics of malaria that ravaged the Southern U.S.
Colonialism’s effects on malaria were not restricted to its spread, however. Even in areas where malaria was already present, colonial influence often worsened conditions and caused epidemics.
In the southern African country of Swaziland, malaria was common but nonfatal before colonial intervention. This was due to the immunity that can be acquired with repeated exposure. When colonists arrived, however, they removed Swazi inhabitants from their homelands, forcing them to move into lowlands with larger mosquito populations.
Taxes imposed on Swazis, drought conditions, and the exportation of Swazi crops led to famines that left the Swazi people vulnerable to malarial infection. Droughts would temporarily relieve infections but at the cost of losing acquired immunity. Famines forced many Swazis to travel to find work and food, but travelling labourers would lose their acquired immunities, leaving themselves vulnerable to infection upon their return.