Malaria: Invasion and Colonization of Red Blood Cells by Merozoites - Dr. Mramba Nyindo

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Tropical Parasitology: Protozoans, Worms, Vectors and Human Diseases

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Duke University

Tropical Parasitology: Protozoans, Worms, Vectors and Human Diseases

180 ratings

This course provides students an understanding of important human parasitic diseases, including their life cycles, vectors of transmission, distribution and epidemiology, pathophysiology and clinical manifestations, treatment, and prevention and control. Tropical Parasitology is taught by faculty from an area highly impacted by tropical parasites- the Kilimanjaro Christian Medical University College in Moshi, Tanzania. The faculty include Drs. Frank Mosha and Mramba Nyindo (and two lecturers, Drs. Johnson Matowo and Jovin Kitau). Dr. John Bartlett, Professor of Medicine, Global Health and Nursing at Duke University, joins his faculty colleagues in this effort.

From the lesson

Protozoans

We are excited to begin our Protozoa cluster, focusing on malaria, trypanosomiasis, toxoplasmosis, and leishmaniasis. Despite advances in prevention and treatment, protozoal diseases contribute substantially to the global burden of morbidity and mortality. This cluster has a total of 153 minutes of video and 85 pages of reading spread out over the four lessons. Each lesson has all of the readings, lectures, and additional materials to help you understand the topic. You will have unlimited opportunities to take an untimed quiz after you’ve mastered the material in each lesson, and you have four quizzes to complete in this cluster. (Note: this cluster includes a case study practice quiz, ungraded, which is optional). This cluster kicks off with a close look at malaria vectors and the fascinating research being done on diagnosing, treating, and vaccinating against malaria. This is by far the largest cluster in the course, so you have up to 3 weeks to complete this cluster.

Malaria: Vectors - Dr. Johnson Matowo4:00

Malaria: Vector Control - Dr. Johnson Matowo6:59

Malaria: Insecticide Resistance and Management - Dr. Johnson Matowo 11:34

Malaria: Epidemiology - Dr. Franklin Mosha8:28

Malaria: Mosquito Breeding Sites - Dr. Franklin Mosha 0:43

Malaria: The Parasite in the Human Body - Dr. Mramba Nyindo11:46

Malaria: Invasion and Colonization of Red Blood Cells by Merozoites - Dr. Mramba Nyindo 6:58

Malaria: The Parasite in the Mosquito - Dr. Mramba Nyindo 7:29

Malaria: Pathophysiology - Dr. John Bartlett7:38

Malaria: Interview with Dr. Venance Maro 4:12

Malaria: Interview with Dr. William Howlett 4:17

Meet the Instructors

John A. Bartlett, M.D.
Professor of Medicine, Global Health and Nursing at Duke University Medical Center
Duke Global Health Institute
Franklin Mosha, Ph.D.
Professor of Parasitology and Medical Entomology
Mramba Nyindo, Ph.D.
Associate Professor, Kilimanjaro Christian Medical University College (KCMU Co.)

So, let's look about number two, invasion of red blood cells by merozoites.

This is part two.

How do merozoites invade the red blood cell?

I have called it an elegant event.

Highly majestic.

Parasite will engage, binding receptors on red blood cells.

It then undergoes, it undergoes apical orientation.

We'll look at the apex of these merozoites. They are,

the formation of a junction with the red blood cell.

This event is necessary for initiation of signaling

required for release of products from that parasite.

So that it can go

into the red blood cell.

What is important that as it moves here, it creates a vacuole.

This vacuole is derived from the red blood cell plasma membrane.

It will negotiate several.

Taking advantage of the vacuole, which means that

the parasite in the red blood cell, they are not in direct contact.

This mechanism, if you have remembered from cell physiology,

is termed the actin-myosin, moving-junction process.

That's the way, it accesses, that's the way it gets into the red blood cell.

The parasite has

organelles you call rhoptries and micronemes and dense granules.

These three organelles, they contain enzymatic substances,

which will facilitate parasite invasion of the red blood cell.

Something must happen to digest some protein material.

All the red blood cell, for this parasite to reach, its destination.

The interior of the red blood cell.

Malaria parasites have intracellular signaling pathways,

which are actually mediated by phosphoinositide, Cyclic AMP,

and other Calcium dependent mechanisms.

It's an active process.

The vacuole and the cystostome.

So the vacuole I've already said it creates a situation where this

parasite is not in direct contact with the red blood cell.

However, there is an area we call the cytostome, or the feeding apparatus.

And it is at the cytostome that the parasite

takes a chunk, sorry about that.

A chunk of the cytoplasm of the red blood cell and

that feeding process, when it happens and what not, it will end up

in a state of anemia, which is a very important lesion if

you want to call it in the infection of humans with a plasmodium parasite.

Hemozoin, let's talk about hemozoin.

The chunk of red blood cell and cytoplasm taken by the merozoite,

at the feeding will contain a very important molecule, hemoglobin.

The parasite will digest the hemoglobin, but this parasite is not able

to ingest it, to digest the iron component, which we call the heme.

You find in babesia there are no malaria pigments,

because digestion is complete in babesiosis.

This is actually a picture of the merozoite, this is the epical end.

We have talked about orientation, epical orientation.

If this is a red blood cell here, this part outside, if it was facing that way,

it will change the apex, to come into contact with a red blood cell.

These are the, what we call here, the organelles, important organelles.

There is the rhoptery, the conoid and, dense granules.

I think granules are there.

These are released, after a signaling, and

it facilitate parasite invasion, of the red blood cell.

Here is actually what is called the cytostome,

this is the feeding apparatus of this parasite.

Eh, these are

apicomplexa sporozoites, or merozoites.

They look the same.

This is how they access the red blood cell.

As I said, it is very majestic, and we’ll see it very soon.

For example here, merozoite contact with a red blood cell.

This is the merozoite here.

It has initiated contact here.

With this is the red blood cell.

It has released those goodies, which will facilitate its entry.

You see here it has moved in slightly more.

It has even removed farther.

Note this juncture, otherwise things will spill out.

There must be a juncture.

This is your vacuole.

And here, this parasite has kind of turned over somehow.

And it is about three-quarter of its way into the red blood cell.

And this is the merozoite.

Let's move on.

Ha, this fellow, this merozoite!

This is the red blood cell, and this is the parasite

already occupying the cytoplasm of the red blood cell.

This is the area of some contact here.

It is our hope, if your feed the hemoglobin, and to give you the anemia.

It is protected from any immunological attack.

Because it is intracellular for all purposes in the red blood cells.

This end of part two of this presentation.

We shall move to part three very soon.

Thank you for listening.

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