Global malaria attacks double WHO estimates

Main Category: Tropical Diseases
Article Date: 10 Mar 2005 - 11:00 PDT


At least 500 million people have malaria, twice as many as the 273 million estimated by WHO, according to Bob Snow who works at the Kenyan Medical Research Institute, Kenya. Most cases are in Sub-Saharan Africa. However, South East Asia accounts for one quarter of the total.

You can read the full report in the journal Nature .

What is Malaria?

Malaria is a potentially fatal blood disease caused by a parasite that is transmitted to human and animal hosts by the Anopheles mosquito. The human parasite, Plasmodium falciparum, is dangerous not only be cause it digests the red blood cell's hemoglobin, but also because it changes the adhesive properties of the cell it inhabits. This change in turn causes the cell to stick to the walls of blood vessels. It becomes especially dangerous when the infected blood cells stick to the capillaries in the brain, obstructing blood flow, a condition called cerebral malaria. Scientists using the x-ray microscope are hoping to learn more about the how the parasite infects and disrupts the blood cells and the blood vessels of an infected host.

The life cycle of the malaria parasite in a human or animal begins when an infected mosquito transmits malaria sporozoites to a new host. The sporozoites travel to the liver, where they invade hepatocytes (liver cells) and multiply thousands of times over the following two weeks before rupturing out of the liver into the blood stream. During the first 48 hours after infecting a red blood cell, a parasite goes through several phases of development . The first phase is the ring stage, in which the parasite begins to metabolize hemoglobin. The next phase is the trophozoite stage, during which the parasite metabolizes most of the hemoglobin, gets larger, and prepares to reproduce more parasites. Finally, the parasite divides asexually to form a multinucleated schizont. At the end of the cycle, the red blood cell bursts open and the parasites are dispersed to infect more red blood cells.

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