Are blood genotypes really consequential in malarial infections?

Four days ago, I came down with symptoms of flu. Even though it was still early, I knew I was about to pass through another bout with my regular customer, the malaria. The last time I had it was like four months ago. The longest I have gone without coming down with the disease was six months.

Rightly so, two days after the initial symptoms of sneezing and watery nose, I came down with full blown malaria. How did I know I was gonna have malaria? The answer is quite simple, I have AA blood genotype (not blood group please) and I stay within the tropical region. By now, an inquisitive mind would probably be asking what correlation there is between malaria, AA blood genotype and living in the tropics. I will start with the later.

Malaria is an endemic disease within the tropics and sub-tropics, caused by a parasitic protozoan known as Plasmodium and usually transmitted by an insect vector known as the Anopheles mosquito. An endemic disease is one that occur regularly among populations confined to a particular region or area. Tropical regions are regions covering the area between 231/2^O North and South of the equator. The area is made up of tropic of Capricon in the Northern hemisphere of the earth and tropic of Cancer in the southern hemisphere of the earth respectively.

^{World atlas showin tropical regions: By KVDP - CC BY-SA 3.0, Link}

The tropical regions are the hottest regions of the earth with peculiar weather and climate which serve to delimit biological diversity. Organism that survives and thrives within one region with peculiar abiotic factors may largely not survive in another region of different abiotic factors. Specifically, the generally high temperature of tropical area is required in order for the malaria parasite to successfully complete its life cycle which usually takes place within the guts of female Anopheles mosquito. Hence, malaria transmission will and does not occur in areas with temperature below 20^OC even if such areas are within the tropical zone such areas of high altitudes.

Now to the blood genotype brouhaha. Individuals with the AA blood genotype have been reported to be more susceptible to malarial infection compared to those with AS blood genotype with SS blood genotype individuals being more vulnerable because the condition itself is characterized by crises and deleterious at large. In other to full understand this pattern, a brief understanding of the life cycle ot the Plasmodium parasite would be a bit necessary.

Generally, the life cycle of the Plasmodium parasite involves two hosts, human and another organism that act as vehicular career of the parasite, the female _anopheles mosquito. Multiplication and growth takes place in the liver cells of humans after which the parasite migrates and infect the red cells of the blood, growing and lysing the blood cells in the process. As they grow in and lyse the red blood cells, daughter cells in form of merozoites are released and each one continues the cycle by invading more red blood cells. At this point, an infected human starts showing symptoms of malaria. The blood stage of the parasite is often referred to as the gametocyte stage.

^{Life cycle of Plasmodium: CC By 2.0}

Mosquito generally feeds by sucking on blood of other animals, especially humans. As a result of sucking on blood of Plasmodium infected individuals, specifically if the parasite is at the gametocyte stage, the female Anopheles mosquito picks up the organism and as such, the protozoa starts a different cycle of growing and multiplying within the new host. The parasites are found as sporozoites in the salivary gland of the mosquito 10 to 18 days after being picked up and these sporozoites are easily injected into the blood of another human during another blood feeding session. Thereafter, the parasite starts another journey of its life cycle within the human host. AT this point, it is important to note that while the Plasmodium induce malarial symptoms in human hosts, it does otherwise in the mosquito host. The mosquito just act as a vehicle for the transmission of the organism.

Plasmodium has been studied and found to have perchant for oxygen and hemoglobin consumption. They consume large amount of oxygen and ingest large amount of hemoglobin during their stay in the blood as part of their life cycle. The AA red blood cells have also been studied and reported to have adequate hemoglobin both in quantity and in structure, hence, the AA red blood cells have higher binding capacity to oxygen. The combination of adequate hemoglobin and richness in oxygen makes the AA red blood cells a more conducive site for Plasmodium's multiplication process.

The presence of defective hemoglobin in people carrying the sickle cell traits in their blood (AS) confers some form of protection against the malarial parasite. The polymerization of defective hemoglobin affects the capacity of the parasite to carryout digestion, an important metabolic process for any organism to keep living. In addition, the malaria parasite causes premature rupturing of the blood cells with defective hemoglobin, terminating the fecundity of the parasite as a result. The defective hemoglobin red blood cells less readily adhere to parasitized red cells as compared to normal red cells.

^{By Diana grib - CC BY-SA 4.0, Link}

However, the semi-immunity to malaria parasite conferred by defective hemoglobin does not extend to those with sickle cell anemia. In actual fact, they are more susceptible to malaria and should be protected as much as possible from getting infected with the disease.

In order to answer the ultimate question that constituted the title of this article, yes! Blood genotypes actually have a role to play in malarial infections as explained above.

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Conclusion

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Some folks in the steemstem discord channel were a bit perplexed when I told them I was going to come down with malaria.

Isn't malaria a deadly disease?

Yes! malaria use to be and it is still a deadly disease in some tropical regions of the world where accessibility to treatment is either very expensive or lacking. Actually, if what I have heard about malaria is anything to go by (do'nt mind me, I'm probably too lazy to find out), the disease claimed more lives than what Human Immunodeficiency Virus has claimed so far before the first effective treatment was found in form of quinine isolated from plant.

^{Antimalaria drug: Image taken using Samsung Galaxy A10}

Majority of those that are not familiar with the malaria menace would probably be wondering why I did not visit a physician or a laboratory to have my system assessed. But yea, I know and understand my malarial symptoms like the lines in the palm of my hands. Coupled with the fact that the majority antimalarial drugs are easily sold over the counter (requires no prescription), I was not ready to go and throw away some hard earned fiats just to confirm what I already know. So, above is a picture of the antimalarial drug I bought. I started taking it yesterday and I feel strong enough to write this post today; coincidence? I dont think so. The complete dose ends in three days.

Thank you all for reading.

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References

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CDC

New Scientists

National Library

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