Malaria blocks 'super-infection'

15 May 2011 Last updated at 17:04 GMT People can be bitten by 700 malaria-infected mosquitoes a year in some countries The malaria parasite can ensure it keeps a host body all to itself by preventing further malarial infections, according to international researchers.

The parasite initially reproduces in the liver and moves into the blood.

A study on mice, published in Nature Medicine, showed the parasite can trigger iron deficiency in the liver and therefore prevent more infections.

An expert said the research was "very cool and very interesting", and improved understanding of infection.

The researchers were looking at super-infections, when a patient already infected with malaria is infected with another batch of malaria parasites.

People in high-risk areas can be bitten by up to 700 different malaria-infected mosquitoes each year.

Protecting turf

In experiments on mice, researchers showed that parasites in the blood were able to stimulate the production of the hormone hepcidin, which regulates iron levels.

This reduced the level of iron in the liver, preventing other malaria parasites from reproducing in the organ.

Dr Hal Drakesmith, from the Weatherall Institute at Oxford University, who was part of the Medical Research Council team, said: "Now that we understand how malaria parasites protect their territory in the body from competitor parasites, we may be able to enhance this natural defence mechanism to combat the risk of malaria infections."

Malaria is often accompanied by anaemia, which is treated with iron supplements.

In this study, mice given iron supplements were more susceptible to additional infections.

Dr Drakesmith said: "We may need to look again at the advisability of iron supplementation programmes in malaria-endemic regions, as possible increased risk of infection may need to be weighed against benefits."

Dr Rita Tewari, a malaria researcher at the University of Nottingham, said: "It's very cool and very interesting.

"It tells us a bit more about the mechanism of malaria infection and gives us some sort of tool, this molecule hepcidin, that you can manipulate which can affect infection."

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