|Plasmodium (in yellow) bursting RBCs|
Ask any undergraduate biology student with a few years of classes under their belt to draw you the life cycle of Plasmodium. Go on...I'll wait....Did they do it?...Correctly?...Awesome! The life cycle for this parasite is often one of the first life cycles encountered by students of biology. Let's start with the vector. This parasite is spread via bites from female mosquitoes belonging to the genus Anopheles.
|Anopheles Up Close and Personal|
Outsmarting Our Immune Systems
Plasmodium is a devious little dude. These parasites are largely protected from the treat of a host's immune system because they live within cells rather than outside of them. This hides them from circulating immune police, such as macrophages. However, erythrocytes are prone to aging because they work so hard for our bodies. When these cells pass through the spleen, they are checked for signs of damage or aging, and are subsequently filtered out of regular circulation. The parasites becomes the cutting edge of anti-aging technology for these little cells by using proteins to prop up the cells, making them seem young to the busy spleen, and saving the parasites' homes for another road trip through the circulatory system. Some species, such as P. falciparum, will even go so far as to produce adhesive proteins that force cells to stick to walls of small vessels in order to save themselves from being processed via the spleen.
Symptoms of Malaria
The symptoms of malaria may not appear until 8-30 days post-infection. As the parasites enter into the phase of their life cycle in which they invade erythrocytes and force them to burst, people tend to spike fevers. In some instances, people infected by P. viviax won't display symptoms for several months or even years post-infection. This is because this species produces hypnozoites, which allow for long incubation periods and late relapses of infections.
The most common symptoms are flu-like in nature: headache, fever, shivering, joint and muscle pain, vomiting...but some are more severe such as anemia, jaundice, and retinal damage. The most defining symptom is paroxysm. Paroxysm is a period of coldness followed by chills and then by high fevers and sweating. The time frame of paroxysm states is dependent upon the type of malarial parasite with which one is infected.
The World Health Organization (WHO) splits malaria cases into two categories: "Severe" and "Uncomplicated". To be classified as "severe", one must demonstrate any of the following: decreased consciousness, significant weakness (e.g. inability to walk), loss of ability to eat, convulsions, low blood pressure, breathing difficulties, circulatory shock, kidney failure, red (hemoglobin-rich) urine, uncontrollable bleeding, enlarged liver, enlarged spleen, pulmonary edema, low blood glucose, acidosis, high levels of lactate, or an extremely high parasite level present in the blood. The disease can progress to an even more severe form (if infected with P. falciparum) known as cerebral malaria. This form presents with neurological problems such as seizures and comas.
Diagnosis, Treatment, and Prevention
Malaria is diagnosed by finding the parasites in a blood sample. This can be through microscopic examinations of blood smears, or through antigen-based diagnostics tests. The later is more accurate, but also more costly, and these tests are not yet sophisticated enough to tell how many parasites are present within a sample. Polymerase Chain Reaction (PCR) has been shown to diagnose malaria efficiently, but is not widely used due to its complexity.
People diagnosed with malaria are usually treated using chloroquine in areas where Plasmodium isn't already resistant. Because resistance is so prevalent, most patients are also given mefloquine, doxycycline, or Malarone. To prevent resistance, many places are now instituting the use of artemisinin-combination therapys (ACTs), which involves treating with traditional anti-malarial medications in conjunction with artemisinin compounds. ACT is about 90% effective if used to treat "uncomplicated" forms of malaria. When treated correctly, patients can experience a complete recovery.
|Various Anti-Malarial Medications|
To prevent malaria, most tropical regions take on a three-pronged approach:
1) They give out prophylactic medications (if they can afford to do so).
2) They work to eliminate Anopheles mosquitoes.
3) They devise ways to prevent people from getting bitten by mosquitoes.
Prophylactic medicines are often the same medicines used for treatment (mefloquine, chloroquine, Malarone, etc.). Travelers heading to malaria-endemic regions begin taking prophylactics a few weeks before leaving and continue taking them for about a month after coming back home. (I personally took Malarone when I traveled to Panama for two weeks, and I didn't have any problems, but many people have side effects of this and other such drugs.) This form of prophylaxis is not typically practical for residents of malaria-endemic areas because drug resistance and partial immunity can come from prolonged use. This is also a costly endeavor, and has had many historical roadblocks.
To prevent mosquito bites, people can use DEET-based repellents and insecticide-treated mosquito nets. Treating the nets with insecticides reduces the chances of mosquitoes living long enough to find a way to breech the nets themselves.
|A woman tucks a mosquito net into her child's mattress.|
Community-aimed educational programs are also helpful in preventing the spread of malaria. After all, knowledge is power! Seriously! Teaching people to cover areas with stagnant water that could become mosquito-breeding grounds, as well as helping people to recognize the signs and symptoms of malaria can greatly reduce the number of malaria cases reported in an area.
|An old poster encouraging people to spray for mosquitoes.|
Ultimately, the best approach would be to prevent malaria rather than to treat it. (More cost effective and less costly in terms of human life.) However, the monetary costs of instituting a program for prevention are beyond the means of the countries where malaria posses the biggest threat to public health. Luckily, there are some amazing researchers (namely Jay Keasling...go on...Google him!) working to produce an anti-malarial drug that can be mass-produced cheaply. Thanks to this kind of research, and humanitarian efforts directed at distribution, the next few decades are sure to reduce the number of annual cases of malaria. It will be interesting to see how things change from a socio-economical perspective in response to a decline in a disease with such wide-reaching impacts on global health and economies.
Moral of the Story
Though I could go on and on and on about malaria, this post has already gotten rather lengthy, so we will call it quits for today. Maybe a future post will discuss the amazing way some populations have developed genes that prevent them from contracting malaria...or we could delve deeper into the work of Jay Keasling. Perhaps a future post could discuss the history of malaria, an exciting tale of man's ups and downs as he fights to erradicate a disease that just won't seem to die. For now, at least you can proudly say that you know the basics about malaria. So if you ever travel to malaria-endemic areas, be sure to take your antimalarials (before, during, and after), sleep with a special insecticide-drenched, netted canopy surrounding your bed, and be sure to invest in plenty of DEET!
|P. falciparum...because I can't resist a rainbow-colored image! |
(Even if it is artificially done! :p)