The link between sickle cell disease and malaria is a very good example of how genetic variation can provide immunity from diseases. The malaria parasite fails to thrive in a person with sickle cell trait. This gives him immunity from malaria. The
The human red blood cells are disc-like and roughly concave in shape. When a person starts to suffer from sickle cell disease, the cells become shaped like a sickle. This has the effect of reducing their capacity to carry oxygen. It leads to anaemia, lung problems and strokes. Genetically speaking, a particular gene HBB releases a protein called beta haemoglobin which makes the red blood cells sickle shaped. It is an abnormal kind of haemoglobin. Now, the sickle cell disease is an inherited genetic disorder and has some effect on the malaria parasite.
If a person receives this problem gene from both his parents, he is sure to develop this disease and die prematurely. In case, the person receives this gene from only one of his parents, just a few of his body cells would be sickle shaped. Such people are often only the carriers of the mutated gene.
How Sickle Cell Disease and Malaria are Linked
Presence of sickle cells in a person is believed to provide resistance to malaria parasite for people living in areas which are endemic. This is clear from the fact that in the African lowlands, where malaria is endemic, the incidence of individuals with sickle cells is high, as compared to the African highlands.
Various explanations have been given for this phenomenon –
- When the malaria parasite enters the bloodstream of a person with sickle cell trait, the red blood cells break down and do not allow the parasite to continue its lifecycle. In other words, it is not able to get the required conditions necessary for its survival.
- The malaria parasite needs haemoglobin to grow. It is not able to continue its growth with the beta haemoglobin released by genes that cause sickle cell disease.
- Since the oxygen concentration of red blood cells in people with sickle cell trait is low, the malaria parasite reduces it even further, leading to its destruction.
- The low oxygen concentration has another effect on sickle cells. The potassium of these cells leaks. Potassium is needed by the malaria parasite for its growth which it is not able to get.
Although, the above explanation is plausible and very convincing, more research on this association of sickle cells and immunity from malaria is needed. Sickle cell disease is surely one of nature’s ways of doing the balancing act.
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