Week of Silence: Malaria

The mosquito is the only insect capable of carrying the human malaria parasite, known as plasmodia. After penetrating the skin with her syringe-like mouth through a thin layer of fat and into the capillaries, the infected female mosquito of the genus Anopheles begins to drink the blood. To prevent the blood from coagulating, she oils the affected area with her saliva. At this point in her feeding, tiny malaria worms that she carries in her salivary glands are sprayed into the victim’s bloodstream. About 50,000 are inserted, but it only takes one to kill a child.

Malaria is prevalent in over 106 countries and affects just over half the world’s population. The disease itself has grown resistance to drugs and its most potent strain, Plasmodium falciparum, can’t be controlled. Of the half billion people who are affected by it, one million die, most of them being just under five years of age from Sub-Sahara Africa.

From the mosquito’s salivary glands to the victim’s circulatory system, the parasite travels to the liver where malaria makes itself comfortable and begins to digest the liver cells immediately. While the parasite eats and multiplies, the victim shows no symptoms and feels no change in his or her body for roughly a week. During this week of silence, each falciparum has multiplied itself 40,000 times. After being digested through and through, the liver cells explode and the parasites are let into the bloodstream entering each red blood cell devouring and proliferating.

In this second week, the body starts to feel ambushed. The victim’s temperature begins to rise in order to cook away the parasite and shivers in order to produce more heat. It is then followed by drenching sweats in order to cool the victim back down. While the victim goes through this agonizing cycle, there are billions of parasites in the blood, continuing to multiply. Meanwhile, the infected cells pass through the capillaries of the brain and latch on so as to not pass through the spleen, whose job is to clean blood by destroying tainted cells. At this point the brain starts to swell; this is known as cerebral malaria.

Scientists around the world have been desperately trying to find new drugs to stop the malaria parasite and prevent the disease from spreading. Malaria is spread so widely in Africa, it is very difficult to control, even with all the international funding and private donations. There has been an anti-malaria gene located in sickle-cell anemia patients demonstrating that those with HbC are less likely to become sick with malaria compared to normal HbA people. However, this mutation is not more prevalent in Africa because the negative effects of sickle cell anemia outweigh the resistance to malaria.

Update:

When the body starts to break down physically, the parasites have destroyed so many oxygen-carrying red cells that too few are left to sustain vital functions. The lungs fight for breath, and the heart struggles to pump. The blood acidifies and many brain cells die.

Sickle-cell anemia is the result of a faulty hemoglobin molecule. Hemoglobin molecules of homozygotes behave abnormally after releasing their oxygen. Instead of remaining soluble in the cytoplasm, they combine to form long fibers that deform the red blood cell from a normal biconcave disk to a sickle shape.

The deformed cells clog the small blood vessels, reducing oxygen flow to the tissues and giving rise to muscle cramps, shortness of breath and fatigue. The sickle cells are also very fragile and easily broken. Homozygotes are resistant to malaria because when the parasites try multiplying in the cell, the sickle cell breaks down before the malaria parasite can proliferate.

In areas where malaria is endemic, heterozygotes are better able to survive and pass on their genes than are either type of homozygote. Homozygotes sickle cell individuals often die of sickle cell disease while those who are normal homozygotes often die of malaria. Heterozygotes are relatively immune to both conditions. Understanding how the gene prevents severe malaria could lead to the development of protective drugs.


Posted by Sarah Bello (1)