This document discusses the relationship between sickle cell anemia and malaria. It notes that individuals with the sickle cell trait (AS genotype) have some protection against malaria. This is because their red blood cells can still produce enough normal cells to avoid severe effects of sickle cell anemia, but also enough sickle cells that confer resistance to the malaria parasite. The document hypothesizes that when a red blood cell with the sickle cell trait is infected by the malaria parasite, it undergoes sickling which allows it to be more easily captured by macrophages before the parasite can complete its lifecycle.

1. Sickle Cell
Anaemia and
Malaria
Dr Nishantha Wickramanayaka, MD
nishanthaw@live.com
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2. Introduction
• Sickle cell anaemia is a major topic within haemolytic anaemias and
its epidemiology is a remarkable signature of the past and present
world distribution of Plasmodium falciparum malaria.
• There are close and complex relationship between this blood disease
and this infectious disease.
• Heterozygotes for the sickle gene (AS) are relatively protected against
the danger of malaria. This is now firmly established through a
number of clinical field studies from different parts of Africa.
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3. Inheritance of Sickle Cell Anaemia
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5. Correlation between sickle cell disease and
malaria
• In areas where malaria is common, there is a higher incidence of people
who are heterozygous(AS).
• These individuals produce enough normal blood cells to avoid the more
severe effects associated with sickle cell anaemia, but also produce
enough sickle cells to confer an increased resistance to the malarial
parasite.
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6. Genotype and susceptibility of Malaria
• Opara,K.N, have reported children with genotype AA (92.3%) were
more susceptible to malaria parasite than AS (5.1%) and SS (2.6%).
• Another study done in Burkina Faso, have found in a cohort of
children, AS genotype was associated with lower risk of clinical
malaria relative to AA genotype.
• However, many others have reported, that the genotype AS is more
protective from complication of P.falciparum.
• Several possible mechanism have proposed to explain resistivity of
(AS) to P.falciparum.
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7. How AS
Survives
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8. Possible explanation
• The upper part of the diagram shows what happens in red cells in a
normal (Hb AA) person with malaria.
• After invasion of a red cell by a merozoite, this becomes a ring form,
and this starts multiplying (schizogony).
• When a schizont is mature the infected red cell essentially bursts and
releases new merozoites, each one of which can invade a new red cell.
• The lower part of the diagram of what happens in red cells in an AS
heterozygote with malaria.
.
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9. Possible explanation, Cont.
• The red cell, which appears normal at the time of invasion, once
infected undergoes sickling as a result of deoxygenation and lowering
pH caused by the parasite).
• Thus it falls easy prey to macrophages in the spleen, in other organs
and even in the peripheral blood. Phagocytosis of a parasitized red
cells clearly interrupts the schizogonic cycle and thus the parasitaemia
can be kept under control.
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