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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.
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Female Anopheles mosquito
taking a blood meal |
A large swamp which would
make an ideal breeding site for Anopheles mosquitoes
- Image from Lines JD
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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. |
Child with cerebral malaria |
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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