Tuesday, October 28, 2008

Infection: Malaria

I vant to suck your blood!

What better time than Halloween to be thinking about blood suckers. The one you see to the right is Anopheles mosquito, and its bite probably doesn't even hurt, though it might itch later. 41% of the world's population lives in the home territory of these little vampires, but the loss of blood isn't that harmful. What your characters have to be wary of is the VTD - Vampire Transmitted Disease. Anopheles mosquitos are often infected with tiny, microscopic parasites that are the cause of one of the most common parasitic diseases in the world - malaria.

Every year around the world, 350-500 million cases of malaria are diagnosed. This disease is anything but rare.

Malaria is caused by several species of parasites - P. falciparum, P. vivax, P. ovale, and P. malariae. These yummy little microscopic bugs have a powerful hunger for red blood cells. The parasites are injected into the body through the bite of infected mosquitoes. Once injected, they race to the liver and begin to multiply. Victims rarely know they are infested during this stage as the 15-100 parasites build an army 30,000 strong before attacking the choice buffet that is the blood stream.

Once inside the blood cells, the parasites multiply and feed, eventually rupturing the blood cell and causing the symptoms of malaria. Symptoms begin anywhere from 7 to 30 days after the mosquito bite, but can be suppressed up to a year by modern anti-malarial drugs. How fast the symptoms start depends on which species of the parasite are infecting the person, and on the person's own body. Classical malaria attacks are rarely observed these days, but attacks occur every 2-3 days and last 6-10 hours each. The reason for this timing is that the parasites incubate inside infected red blood cells for 2-3 days before the blood cells rupture. In classical episodes, the victim goes through three distinct stages of illness.


  • The cold stage - shivering, chills

  • The hot stage - headaches, fever, possibly seizures (especially in children), vomiting

  • The sweating stage - sweats, normal temperature, extreme tiredness
In general, a victim can experience any of the following symptoms, in any order: chills, fever, weakness, vomiting, sweats, headaches, nausea, muscle aches and generally feeling under the weather. In cases of infection with P. falciparum jaundice (yellowing of the skin and whites of the eyes) can occur along with enlargement of the liver and fast breathing.

Right. Sounds like a nasty case of the flu. What's the big deal?

Malaria infection killed nearly a million people in 1995 alone, and accounts for over 10% of all childhood death in developing nations. The strain of parasite, P. falciparum, are much more aggressive than the others and can lead to "severe malaria" in which one or more organ system fails to function. Systems and their symptoms are listed below:

  • Brain infection - abnormal behavior, seizures, decreased ability to remain awake, coma or death

  • Severe anemia leading to extreme tiredness and breathing trouble

  • Respiratory distress (breathing trouble) - flaring of the nose, head bobbing, panting, fast breathing, blue tinge to the fingertips, lips or mouth, the inability to get enough air, passing out, death

  • Longer bleeding times before clotting - this can lead to strokes, bruising, actual bleeding, gut-bleeds (bloody or coffee-ground appearance to the poop), bloody urine, etc..

  • Cardiovascular collapse (failure of the blood stream to hold enough fluid in to meet the body's needs or failure of the heart to pump blood) - symptoms can include chest pain or difficulty breathing or may mimic shock - low blood pressure, loss of consciousness, rapid heart rate, shaking, cold extremities, sweating, lightheadedness, confusion

  • Low blood sugar (starving the brain) - symptoms include dizziness, hunger, headache, shaking, anxiety, and heart palpitations (feels like your heart's doing flip-flops in your chest. On this I speak from experience)
Today, treatment with antimalarial agents reduces the severity and duration of malaria infection. A list of drugs used appears below, taken from the Centers for Disease Control website.

chloroquine
sulfadoxine-pyrimethamine (FansidarĀ®)
mefloquine (LariamĀ®)
atovaquone-proguanil (MalaroneĀ®)
quinine (Best bet for pre-modern settings)
doxycycline
artemisin derivatives (not licensed for use in the United
States, but often found overseas)

One more nasty little surprise, malaria caused by the P. ovale or P. vivix strains can lay dormant for months to years in the liver, eventually re-emerging to cause symptoms all over again.

A pound of prevention

Currently, the gold standard for prevention of malaria is using mosquito netting around beds and cribs to prevent mosquito bites. A multitude of non-profit organizations exist whose mission it is to send mosquito netting to poor and under-served populations in areas where malaria is endemic. Other methods include draining wet areas and eliminating standing water where mosquitoes breed, using pesticides to reduce mosquito populations, and using anti-malaria drugs prophylactically (to prevent infection) for pregnant women and individuals traveling to areas where the infection is endemic (native).

An evolutionary twist

One of the most fascinating phenomenon I studied in nursing school was Sickle Cell Anemia. This disorder is a genetic change to the shape of red blood cells that can cause severe problems and even death in those who are symptomatic. However, the trait for Sickle Cell disease actually conveys a protective factor against malaria infection! Considering that this trait developed in the part of the world where malaria have been endemic for the whole of human history, it's interesting that a twist of genetic selection could breed a trait to keep people from getting sick.

Despite this protective factor, those who develop full-blown sickling, where many red blood cells actually change shape to resemble a curved sickle (see picture), can have life-long severe pain and complications.

Addendum - you can find a map of the parts of the world where malaria is currently endemic (native) at the World Health Organization's website, this URL http://www.who.int/malaria/malariaendemiccountries.html.

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