Therapy Analysis - Malaria
Malaria - an ongoing challenge
Malaria is one of the largest health crises facing the world today, with 400-900 million people becoming infected with the disease each year, resulting in over a million deaths annually.
Children under the age of 5 are particularly prone to infection, and as a direct result of their immature immunity to disease, make up a dramatic proportion of the deaths each year. Sadly, even children lucky enough to survive an episode of severe malaria are likely to suffer from permanent brain damage. Pregnant women are also highly attractive to mosquitoes and frequently contract the malarial infection as a consequence of their weakened immune system.
In fact, malaria is one of the major causes of perinatal mortality, low birth weight and maternal anaemia. Malaria is endemic in over 100 countries; however the vast majority (90%) of all malaria cases occur in sub-Saharan Africa.
The malaria parasite has been present in humans for over 50,000 years and has put an enormous amount of selective pressure on the human genome due to the high level of morbidity and mortality associated with the disease. One well-studied example of malaria's influence is seen in individuals genotypically heterozygous for sickle-cell disease. The autosomal recessive disease is caused by a mutation in the beta globin gene, resulting in a substitution of valine for glutamic acid and the subsequent distortion of the red blood cell into the characteristic 'sickle' shape. The sickle cells are rapidly eliminated from the blood causing severe anaemia and reduced life expectancy in individuals homozygous for the mutation.
Heterozygotes suffer from a mild anaemia, however, as the merozoite stage of the malarial parasite lives exclusively in red blood cells, these individuals also display a greatly reduced risk of serious malaria infection. In endemic malaria regions the mutation is believed to have emerged independently at least four times and the 'heterozygote advantage' it confers has lead to the frequency of the mutation remaining at approximately 10% in these populations.
