The two most important things you should know about Malaria and Sickle Cell Anemia in 2021.

Introduction

Sickle cell disease is among the top ten (10) non-communicable diseases with a high fatality rate in Nigeria. As reported by the national treatment guideline for the management of sickle cell disease and the Federal Ministry of Health, 2014. Some level of introduction has already been given about sickle cell disease in the previous session. Malaria is a life-threatening disease caused by Plasmodium parasites, and they're transmitted to people through the bites of infected female Anopheles mosquitoes. It is preventable and curable.

Malaria alone causes millions of death yearly worldwide. Even with that, less attention has been given/giving to it. Malaria is caused by a parasite known as Plasmodium and at least four (4) species of this parasite exist, these include; P. falciparum, P. malariae, P. vivax, and P. ovale.

Note that the scope of this work does not cover treatment and/or management of any of the diseases.

Malaria and the human factor (sickle cell trait)

Biological characteristics and behavioral traits can influence an individual’s risk of developing malaria and, on a larger scale, the intensity of transmission in a population.

Persons who are negative for the Duffy blood group have red blood cells that are resistant to infection by P. vivax. Since the majority of Africans are Duffy negative, P. vivax is rare in Africa, especially in West Africa. In that area, the niche of P. vivax has been taken over by P. ovale, a very similar parasite that does infect Duffy-negative persons.

This Duffy gene is a glycoprotein secreted by the blood in response to inflammation. It’s the receptor for P. vivax without this, the organism can not cause infection.

Sickle cell trait is another form of these human factors. The Federal Ministry of health 2014, estimated that about 24% of adult Nigerians have this sickle cell trait and those with this trait are offered some level of protection against malaria.

Relationship between sickle cell trait and malaria

Malaria and sickle cell disease are endemic in sub-Saharan Africa.

J. B. S Haldane 1915 demonstrated genetic linkage in mammals and speculated that,

depending on their genetic makeup, people would have a different risk of dying when they are confronted by a parasitic organism: so much so, that even if a gene offering protection against that parasite was otherwise harmful, its frequency would increase when a population was exposed to the parasite.

Haldane later hypothesized that one important example could be thalassemia in the face of malaria.

The malaria parasite feeds on the human blood when it gets into the body. Rapidly growing malaria parasites in the body need a large number of amino acids but the de-novo synthesis of these amino acids is limited. The parasites, however, use the amino acid composition of the red blood cell.

The red blood cell has two components; heme and globulin. The parasite feeds on the globulin leaving behind heme, this substance (heme) is toxic to both cells of the body and the parasite itself.

The Plasmodium parasite polymerizes this toxic heme substance into a crystalline substance called hemozoin, hemozoin is less toxic to the parasite. This polymerization process is the target for the aminoquinoline e.g Chloroquine antimalaria. This class of anti-malaria inhibits the polymerization of heme to hemozoin and this leads to the accumulation of this toxic substance called heme. This could explain anemia as a side effect of this drug, as heme also destroys hemoglobin when present in an appreciable amount in the blood. Sickle cell hemoglobin (HbS) has a reduced lifespan, and there is a constant breaking down of these cells into its components (Heme and globulin). From hemoglobin, the globulin chains are separated, there are hydrolyzed and the amino acids are channeled into the body amino acid pool. The iron liberated from heme is re-utilized but the body system has a very poor way of handling iron in the body. This could explain why the use of iron in the management of sickle cell disease is contraindicated. In sickle cell disease where there is constant breaking down of hemoglobin, the resulting excess iron accumulates in the system like the cardiopulmonary system. This accumulation has been said to be the major cause of organ failure in this system. In heterozygous individuals, for example, the breakdown of the HbS causes some level of accumulation of heme which in turn offers protection against malaria infection in the individuals.

Miguel Soares and Ana Ferreira of the Gulbenkian Institute of Science in Oeiras, Portugal, and colleagues found that heme which is a component of hemoglobin is present in a free form in the blood of mice with sickle cell trait, but largely absent from normal mice in their research.

Conclusion

There is a complex relationship between sickle cell disease (blood disease) and malaria (blood infectious disease). While the sickle cell hemoglobin (HbS) offers protection against malaria in the heterozygous individuals, in homozygous individuals, this protection may not be felt and patients may suffer a very severe form of malaria. This may be due to two different reasons and there are important to know;

1. Malaria causes anemia which makes sickle cell anemia more severe. This is because a sickle cell patient is already anemic.

2. In sickle cell disease, there is reduced splenic functioning and thus reduces the clearance of the malaria parasite.

There should always be a provision for routine prophylaxis of malaria, especially in homozygous individuals.

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