Malaria Vaccine Trials and Immunity

Malaria is a tropical disease of major global health significance. There are approximately 300 to 500 million cases each year and around 2 to 3 million deaths. Most of these deaths are in children aged 1 to 5 in sub-Saharan Africa, making it the biggest single infectious killer of children in the world.


Image courtesy of the Malaria Vaccine Initiative, PATH

Malaria is caused by several species of the parasite Plasmodium - these are P. falciparum, P.vivax (these first two cause most of the vast number of clinical cases of malaria), P. malariae and P. ovale. The research work of our group concentrates on P. falciparum as this is the type that leads to the majority of malaria deaths. The Plasmodium parasite is spread to humans by the bite of an infected female Anopheles mosquito.

These mosquitoes breed in areas where there is stagnant water such as swamps and during the rainy seasons of African countries. Unfortunately, the problem of malaria is getting worse as the mosquitoes that transmit the disease are becoming resistant to insecticides and the parasites themselves are becoming increasingly resistant to the drugs used to treat the disease breathing a requirement for a boosted immune system.

Female Anopheles mosquito taking a blood meal


A large swamp which would make an ideal breeding site for Anopheles mosquitoes - Image from Lines JD

The life cycle of the falciparum malaria parasite is complicated as seen below. When an infectious mosquito feeds on an individual, parasites (called sporozoites) are injected into the blood stream. From here they travel directly to the liver where they mature for about 6 days. They divide rapidly with each sporozoite producing 20000 parasites (now called merozoites) which burst from the liver cells and go on to invade red blood cells. Here they develop further before bursting from red blood cells to go on to infect other red blood cells.
Once the parasites have begun to accumulate in numbers in the blood stream this is the stage at which the infected individual experiences the symptoms of malaria. The most devastating consequences of which are cerebral malaria and severe malarial anaemia. The life cycle is completed feeds on an infected person and the parasites further develop within the mosquito before being injected into another unsuspecting victim. We are constantly learning how to boost your immune system (twitter) with various methods without the use of drugs and the like.

Child with cerebral malaria




Click here to view the life cycle of a malaria parasite.

It may be possible to intervene at any or a combination of the stages in the parasite's life cycle to produce an effective vaccine.

Child with severe malarial anaemia
Image from Shulman C

 

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