Malaria

Protozoa are unicellular organisms, however unlike bacteria they are Eukaryotes. This means they have membrane bound organelles and are much more complex than bacteria.  

We can break pathogenic protozoa into 3 categories.

Flagellates, Sporozoans and Sarcodinians

One of the most common diseases caused by a protozoa is Malaria.

Malaria is caused by a parasite in the Plasmodium family. In their larval state they are found in the salivary glands of female mosquitoes.

When a mosquito lands on us, they inject their saliva into the blood stream to prevent the blood from coagulating.  

The plasmodium larvae then enters our blood stream

Once in the blood stream the malaria parasite seeks out the liver.

In the liver, they feed and reproduce asexually for roughly 2 weeks.

Once they have matured and multiplied they leave the liver in search for healthy red blood cells.

Once the mature malaria parasites are in the blood stream they can infect healthy red blood cells.

They enter red blood cells and begin to multiple, using the cells resources. By replicating in the red blood cells, the parasite can hide from the bodies immune system.

Before the cell bursts the parasite will split into many larvae (Merozoites).

Once the red blood cells burst, they release merozoites and toxins into the blood stream. This causes high temperature, sweating, shivering and delirium in malaria suffers. In sever cases it can cause death.

Eventually a mosquito will by and drink the infected blood. Thus transporting the malaria parasite to a new host.

The image bellow illustrates the malaria parasite’s life cycle.

So how does the malaria parasite recognise and attach to a red blood cell?

Red blood cells have antigen markers on their surface. ABO, MN, Rh and Duffy groups are specific receptors located on the surface of a red blood cell.

Malaria parasites use the Duffy antigen to recognise and attach to red blood cells.

The image to the left is an exaggeration of blood types A, B, AB and O.

A Genetic Advantage

Sickle cell anaemia

Sickle cell anaemia causes red blood cells to become deformed. They obtain a crescent shape, meaning they can’t carry as much oxygen as normal red blood cells and are prone to blood clotting.

This sounds like a bad thing right? However it is actually an advantage in areas where malaria is extremely common.

Due to their odd shape the malaria parasite can not affect them, meaning the infected won’t be as affected by malaria symptoms.

Duffy group

As I said before the malaria parasite attaches itself to the Duffy antigen marker on red blood cells. The absence of this antigen marker means the malaria parasite can’t attach to the red blood cell.

These two genetic mutations are extremely helpful in Africa where malaria is present.