MALARIA

Facts and statistics of malaria About 40% of the world’s population, are at risk of malaria. Of these 2.5 billion people at risk, more than 500 million become severely ill with malaria every year 1 million die from the effects of the disease. Malaria is especially a serious problem in Africa, where one in every five (20%) childhood deaths is due to the effects of the disease. Every 30 seconds a child dies from maleria. Malaria has infected humans for over 50,000 years, and may have been a human pathogen for the entire history of the species.

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Malaria is caused by a parasite called Plasmodium. It is transmitted via the bites of infected mosquitoes. Only four types of the plasmodium parasite can infect humans Plasmodium falciparum, P.vivax, P.malariae, and P.ovale.

A Plasmodium sporozoite traverses the cytoplasm of a mosquito midgut epithelial cell

How does an infection occur ? people get malaria by being bitten by an infective female Anopheles mosquito. The parasites then multiply in the liver, and infect red blood cells. Only the female Anopheles mosquitoes can transmit malaria, and they must have been infected through a previous blood meal taken from an infected person. When a mosquito bites an infected person, a small amount of blood is taken, which contains microscopic malaria parasites. About one week later, when the mosquito takes its next human blood meal, these parasites mix with the mosquito's saliva and are injected into the person being bitten. In the human body, the parasites multiply in the liver, and then infect red blood cells. The parasites multiply within red blood cells, causing symptoms……

Pathogenesis Maleria develops in two phases exoerythrocytic and an erythrocytic phase Exoerythrocytic phase infects the liver and the erythrocytic phase infects RBCs When an infected mosquito pierces a person's skin to take a blood meal, sporozoites in the mosquito's saliva enter the bloodstream and migrate to the liver. Within 30 mins, the sporozoits infect hepatocytes multiplying asexually and asymptomatically for a period of 6–15 days. Later this yeilds thousands of merozoites, which, following rupture of their host cells, escape into the blood and infect red blood cells, The parasite escapes from the liver undetected by wrapping itself in the cell membrane of the infected host liver cell Within the red blood cells, the parasites multiply further, again asexually, periodically breaking out of their hosts to invade fresh red blood cells. The parasite is relatively protected from attack by the body's immune system because for most of its human life cycle it resides within the liver and blood cells and is relatively invisible to immune surveillance. Infected blood cells are destroyed by the spleen. To avoid this fate, the P. falciparum parasite displays adhesive proteins on the surface of the infected blood cells, causing the blood cells to stick to the walls of small blood vessels. This "stickiness" can cause coma in cerebral maleria, due to the breach of the BBB.

SYMPTOMS The first symptoms of malaria are like having the flu. However a day or so later symptoms worsen – temperature rises to 40 C, shivers, headaches, vomiting, and diarrhoea can be experienced. If you get infected with P. falciparum your malaria can progress to a more severe form (also called complicated malaria) causing symptoms such as: severe anaemia jaundice acute respiratory distress syndrome spontaneous bleeding fits (convulsions) paralysis coma

Prevention and Treatment Medicines can be prescribed for prevention of malaria however these can be very expensive. For standard treatment : Doxycycline - used for most adults. Clindamycin - used for pregnant women and children. Sulphadoxine with pyrimethamine - only used in certain circumstances because resistance to this treatment is high. For prevention of mosquito bites themselves: mosquito nets and mosquito sprays can be used.

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References: aria_disease.html aria_disease.html /en/index.html /en/index.html