Malaria parasites burst blood cells
Malaria is a disease causing many problems in the world. 300 – 500 million persons suffer from malaria, 2 millions die each year and more than half of them are children.
The disease is caused by unicellular parasites of the genus Plasmodium. There are different species that cause different types of malaria. The parasites first live inside mosquitoes and are transferred to humans when the mosquitoes suck blood. The parasites live and multiply inside the red blood cells. At last the blood cells burst, which gives the sick person an attack of fever. This is repeated every two or three days. In Sweden the disease was called ‘every second day ague' in the old times.
The parasites can be killed with different medicines. One of the first malaria medicines was quinine, a substance from the yellow bark tree, Cinchona. One problem is that the parasites gradually have become resistant to several of the medicines. Because of this, new medicines have to be found all the time.
Malaria is nowadays mostly found in the tropics. Since the mosquitoes mainly bite during the night, on of the best protections against the disease is to sleep under a mosquito net. However, most people living in those areas can afford neither mosquito nets nor good medicines and many of them get malaria.
Resistant
Medicines against parasites contain substances poisonous to the parasites. It might happen that the parasite DNA is changed so that it suddenly can tolerate the poison. It has then gained resistance to the medicine and a new medicine has to be found. Resistance also appears in bacteria and viruses.
Yellow bark – the first medicine against malaria
quinine producing bark.
Photo: Carmen Ulloa.
Already in the 17th century a very expensive medicine against fever could be bought in Europe. It was the bark from a tree in Peru named quina-quina, which means ‘the bark among barks' in a South American Indian language. The bark is harvested from some different species of the genus Cinchona (yellow bark tree) belonging to the bedstraw family (Rubiaceae). Those trees are found in the wild in the forests of the Andes in South America.
The medicine has a bitter taste and contains among other substances quinine, which is poisonous to the malaria parasite. When Linnaeus wrote his thesis on malaria he was of the opinion that bitter substances such as quinine did not cure malaria. Later he changed his mind when it was shown that quinine bark was one of the best treatments for malaria patients.
The bark was soon a well-known cure against malaria and other diseases. Large quantities of quinine bark was collected in the wild in South America and shipped to Europe. During the 19th century large Cinchona plantations were established in Asia. Most of the quinine bark was produced in Dutch plantations in Java. It has been said that the Europeans could never have colonised Africa without access to quinine bark.
During the Second World War Java was occupied by Japan and the quinine bark export to Europe stopped. The Europeans had to turn to the forests of South America again to get the important medicine. Quinine bark is not used any longer but has been replaced by several different synthetically produced medicines. Quinine bark is however used as flavouring in bitter soft drinks, such as tonic water.