Question: To what effect does the blood type of a person effect how their body, and the malaria virus, cope and deals with being bitten by parasites, in particular how does the malaria parasite have to adapt and change to attack different blood types? Thanks, Andrew

Julian Rayner answered on 14 Mar 2011:

Hi Andrew, thanks for the question.

Just to clarify, malaria is caused by a single cell parasite called Plasmodium, not by a virus. It might seem a trivial point, but it makes a huge difference – parasites are more complex organisms, have bigger genomes (more genes), and so are much harder to fight.

Generally, differences between humans can make a huge difference in the impact of Plasmodium. The most well-known example is sickle cell disease, which is caused by a mutation in the hemoglobin gene. People with two copies of the mutation get very sick and often die, but people with one copy of the mutation (of which there are many in Africa) do not get sick, and are partly protected against severe malaria.

Blood types are genetic differences that alter the surface of people’s red blood cells. There is only blood type that is known to make a huge difference in malaria infection, called Duffy negativity. Duffy negative people don’t have a certain protein on their red blood cells, and that makes them completely immune to one malaria parasite species, Plasmodium vivax. Most people from west and central Africa are Duffy negative. There is no blood type know to protect against the most deadly human malaria parasite, Plasmodium falciparum, in the same way, but there are several blood groups that may have a partial effect.