What is the nature of the relationship between malaria and sickle cell anaemia?
In persons who have sickle cell anaemia, the amino acid glutamic acid in haemoglobin is replaced with valine. This interferes with conformation of the haemoglobin molecule, and adversely affects its oxygen-carrying capacity. Further, sickled red cells tend to cluster together, and cannot easily move through the blood vessels. The cluster causes a blockage and stops the movement of normal oxygen-carrying blood. This blockage is what causes the painful and damaging complications of sickle cell disease. In 1954, Anthony Allison (among others) hypothesised that sickle cell trait offered protection against malaria. He suggested that those with the trait did not succumb to malaria as often as those without it; but, when they did, their disease was less severe. It is now known that, when invaded by the malarial parasite, normally stable red cells of someone with the sickle cell trait can sickle in a low oxygen environment, such as occurs in the veins. The sickling process destroys the malaria
