Do you know that people with sickle cell trait are protected against malaria?

Sickle cell disease refers to red blood cell disorder where the red blood cell is being destroyed due to abnormal haemoglobin genes inherited from both parents.

Healthy red blood cells are disc-shaped and flexible.[1,2] This allows them to pass through blood vessels to deliver oxygen to cells. The tissues in our body need the oxygen to function normally.

However, in a person with sickle cell anemia, the red blood cells are crescent-shaped and stiff.[2] Because of the shape, the red blood cells tend to stick to the wall of the blood vessels and accumulation of the sickle-shaped red blood cells causes blockage of vessels.[2]

sickle_cell_anemia
Schematics showing health and abnormally shaped red blood cells. Source: NIH

In people who inherited sickle cell disorder, there is a less destructive form where the person inherits only a copy of the abnormal haemoglobin gene.[1] This is called sickle cell trait and the person generally lives a normal live.

Establishing the link between sickle cell trait and malaria

Charles Darwin Theory of Natural Selection reasons that disadvantageous traits would be gradually phased out for the advantageous ones in the same species.[3] This means that people with sickle cell trait would not have existed in today’s time!

Unfortunately, this is not the case as we will see in a video below which maps out how British geneticist Anthony Alison established the brilliant link between malaria and sickle cell trait.

Resistance to malaria

In establishing the connection between malaria and sickle cell anemia, Alison found that there is a high prevalence of people who are carriers of one mutated haemoglobin gene in certain regions of Africa (40% in equatorial Africa[4]), Europe and India. These regions happen to be badly afflicted with malaria as well.

The exact knowledge on how sickle cell trait suffers are protected against malaria remains a mystery until 2011 when a Nature paper published the science behind this resistance.[4]

It was unraveled that the diseased red blood cells compromise the ability of the malaria parasite to survive and reproduce. Again, this is Darwin’s Natural Selection Theory where a deadly inherited disease (deadly only if you acquire both faulty haemoglobin genes) works to protect you from another deadly disease (malaria) which definitely has a greater prognosis as there are medications or precautions you can take.

sickle-cell-and-anemia-link
Regions endemic with malaria showed similarly high prevalence of sickle cell allele predisposition.

Globalisation

The power of globalisation equips people with the ability to travel and settle down to different regions of the world regardless of where they were originally from. This might just be the chance for sickle cell mutations to be eliminated completely. To do this, we must first phase out malaria and we will then, gradually see progress in the fight against sickle cell disease.

References:

[1] Allison AC. Protection Afforded by Sickle-cell Trait Against Subtertian Malarial Infection. British Medical Journal. 1954;1(4857):290-294. Available from: PMC

[2] NIH. Sickle Cell Anemia. Medline Plus; 2016 [cited 2017 Feb 18]. Available from: https://medlineplus.gov/sicklecellanemia.html

[3] Darwin CR. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray; 1859.

[4] Wadman M. Sickle-cell mystery solved. Nature; 2011 [cited 2017 Feb 18]. Available from: http://www.nature.com/news/sickle-cell-mystery-solved-1.9342

Video: https://www.youtube.com/watch?v=Zsbhvl2nVNE

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