Pre- existing Malarial Infection Prevents Super-infection by another Strain of Malaria


In a study whose results can have far reaching implications, researchers led by Maria M. Mota of Instituto de Medicina Molecular in Lisbon, Portugal, in collaboration with researchers at the Weatherall Institute of Molecular Medicine and Oxford University have found that a pre- existing infection of malaria prevents super-infection, by another strain of malarial parasite, in the host. The secondary infection by a different Plasmodium strain is prevented by blocking the availability of iron in the liver, which is important for the development of the malarial parasite.
Malaria is a very common disease in large parts of Africa, Asia, South and Central America affecting millions of people and leading to the death of thousands of children under the age of five. Malaria is caused by the bite of female Anopheles mosquito which transmits the malarial parasite, Plasmodium through blood. Once the malarial parasite enters the blood stream, it is transported to the liver where it multiplies. It then infects the blood cells and gives rise to the symptoms of malaria.
The malarial parasites, whether present in the liver or in the blood, require iron for development. When a person, already infected by malarial parasite, is bitten by another Anopheles mosquito carrying a different strain of Plasmodium, the second strain of parasites enters the host and reach his liver. However, they are not able to grow as the parasites already present in the blood starve the second strain of iron. These findings of the study directly challenge the earlier theory which stated that the infection of the liver cells and that of the blood cells are two biological processes which are independent of each other.
So far, attempts to eradicate malaria have been unsuccessful because of increasing resistance of the mosquitoes to insecticides and the resistance of different plasmodium strains to the various anti- malarial drugs. The findings of this study can have important implications for the management and prevention of malaria world wide. It will also lead to questioning of iron supplementation to children in malaria prone regions, as it may lead to increased risk of secondary infection by a different strain of Plasmodium.