Malaria affects huge numbers of people worldwide: up to 300 million clinical cases, mainly children, emerge each year causing 1.5 to 2.7 million deaths. The disease is caused by a group of parasites called plasmodia. Like all forms of parasites, plasmodia are organisms that need to feed on other organisms in order to survive.
The four different parasites that cause human malaria are: Plasmodium vivax, Plasmodium falciparum, Plasmodium malariae and Plasmodium ovale. They are transmitted by mosquito bites, specifically female mosquitoes, which need a supply of blood to produce and lay eggs. The mosquitoes that transmit human malaria belong to a group called Anopheles. Worldwide, some 400 different mosquitoes belong to this group, and approximately 60 of these transmit the malaria disease. Mosquitoes breed in standing water, which is very common in tropical countries, especially after floods. In colder climates the malaria mosquitoes are not as common, because the low temperatures will kill them. They contract the disease by taking blood from an already infected person, and later pass on the disease when they bite someone else.
The discovery of the parasite in mosquitoes earned the scientist Ronald Ross the Nobel Prize in Physiology or Medicine, 1902. In 1907 Alphonse Laveran received the prize for his findings that the parasite was present in human blood and that it caused the malaria disease.
Symptoms of malaria include fever, shivering, pain in the joints, headache, repeated vomiting, generalized convulsions and coma. If not treated, the most serious kind caused by the P. falciparum parasite, can become deadly within two days. The other malaria parasites cause less serious symptoms, but can weaken a person's immune system, making him/her more vulnerable to other infectious, life-threatening diseases.
By Professor Paul Henri Lambert
First published 9 December 2003