Malaria – The Viscious Cycle

definitely not a mosquito

definitely not a mosquito

Anopheles would make a beautiful name for a daughter wouldn’t it? I mean if my friends set me up on a blind date and they told me that her name was Anopheles I would envision this mind-numbingly gorgeous, Greek goddess of a woman. However, 5 seconds into a google search you would very quickly realize that the name Anopheles has another meaning entirely, a dark, strangely complex story that has shaped human civilization over the eons. (I get so dramatic after I’ve watched “Game of Thrones.”)

This is the story of humans, mosquitoes, and a curiously well adapted parasite responsible for causing a disease known far and wide as “malaria.”
I’ve said it before; we are not alone, and I don’t just mean in the universe. Hell, we aren’t even alone sitting in the bathroom with a Vanity Fair magazine. There are microbes on the sink faucet, and in between the fibers in the carpet. There are viral particles, and fungal spores floating in the air, and no matter how thoroughly you wash your hands with cucumber melon scented soap the bacteria in your gut and the staph bacteria in your mouth could not be happier. Yes my friends, each of us is our own zip code.

So once upon a time our ancient ancestors were dropping like flies from a mysterious disease with no name…well, it had names like “curse from the Gods” and “bad air,” as in Mala = bad + aria = air, but none of those were terribly scientific. Of course, we eventually caught on to the fact that it was mosquitoes that were spreading the disease to humans. Mosquitoes don’t just feed on humans but anything with blood coursing through its veins, also known as “everything.” This makes them the perfect vectors for blood borne diseases. We recognize Anopheles as the genus of mosquitoes that commonly infects humans with malaria, but what exactly is the mosquito carrying?
One of the most ancient and devastating infectious agents to plague humankind is not a bacteria or a virus but a protozoa called Plasmodium falciparum. That’s right a protozoan, one of those curious creatures you read about in biology class and never mentioned again. The chapter on protozoa is like a TV show that only lasted for one season, but they’ve always been here, lurking in the shadows.

Image

Plasmodium gametocyte shown here dead center. At this stage it can be taken up by a mosquito to begin the cycle again.

Plasmodium falciparum (the deadliest form of malaria) is a single, eukaryotic cell that’s life cycle is completely dependent on two hosts. The life cycle of the Plasmodium is pretty freaky stuff. It reads like the plot of a B-rated, 80’s Sci-fi movie starring Matthew Broderick. Its success as a species is completely dependent on the fact that mosquitoes feed on human blood. At one stage male and female gametes of the plasmodium develop in the gut of a mosquito where they have a little, kinky get together to produce fertilized versions of plasmodium. These will form cysts along the walls of the gut like time bombs that eventually rupture to release a demon horde of sporozoites inside the mosquito. These juveniles move into the salivary glands where they can be passed easily into the bloodstream of an unsuspecting human the next time the mosquito feeds.

Once the Plasmodium sporozoites reach the human blood stream they make a mad dash to the liver. They develop in the hepatocytes, dividing until their massive numbers rupture the liver cells, releasing them back into the blood stream where they now invade red cells. Some of these will differentiate yet again into male and female gametocytes. Yes, this is one of those déjà vu moments. If another mosquito drinks the blood of this infected human the cycle will begin again.

You can literally drive yourself mad thinking about where the original Plasmodium came from. It’s a tragically elegant case of chicken and egg. Sure, the cycle starts with the gametocytes in the gut of the mosquito but the gametocytes can ONLY be produced in the human host cells. Where and how did this all begin?

Stay tuned for a part 2 where we will describe how Malaria affects the human body and how we combat it.

As always stay curious, stay classy, and never stop learning my friends 🙂

map depicting the tropical regions with the highest prevalence of malaria.

map depicting the tropical regions with the highest prevalence of malaria.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s