By Trevor Kuntz
25 April 2012
Note: In case you are wondering whether I actually know a lot about malaria or whether I am just copying from somewhere else, I have always been interested in tropical diseases and at one point thought about being a malariologist. I wrote this entirely myself, drawing on materials I have read over the past few years.
As many know, today is World Malaria Day. However, many do not know what malaria is, how it originated, how it has become such a problem, or what we are doing to prevent and cure it. Today, I want to change that. How Malaria Works
First, we need to know how malaria works and how it began. Malaria is caused by the invasion of the human bloodstream by a parasitic protozoan of the genus, Plasmodium. These parasites reproduce sexually inside of the mosquitoes, but do not harm the mosquitoes. After reproducing in the stomach of the mosquito, the parasites, in the form of sporozoites, move into the salivary glands of the female mosquito (only female mosquitoes carry the Plasmodioum parasite and feed on mammals because they need the nutrient-rich blood for egg production while male mosquitoes do not). When the mosquitoes feed on a mammal, the sporozoites leave the salivary glands of the mosquito and enter the bloodstream of the mammal. The sporozoites then move to the host's liver and begin to produce merozoites through nuclear and cellular division. After about a week, these merozoites enter back into the bloodstream where some of the merozoites invade red blood cells while other merozoites circulate in the bloodstream waiting to infect another mosquito. The merozoites that enter the red blood cells consume the host cell's hemoglobin and produce 8 to 16 merozoites. The merozoites break out of the cell, destroying the cell, and the new merozoites repeat the process. This cycle repeats every 2 to 3 days, causing the chills and fevers cycle commonly associated with malaria infection.
Types of Malaria
There are four types of malaria that infect humans: plasmodium malariae, plasmodium vivax, plasmodium ovale, and plasmodium falciparum. Of these, p. falciparum is considered the most dangerous and is the type that most commonly causes death in humans. While the other three types occur over a long period of time and destroy 2% to 5% of a host's blood cells, p. falciparum is very acute and can destroy up to 80% of a host's blood cells, at which point the host will most likely be dead.
Where Did Malaria Come From? Malaria is believed to have originated in either Africa or Southeast Asia, and there are many debates over which region it came from. Regardless of where it originated in, malaria as we know it today mainly came from Africa. Due to the lack of livestock to offer mosquitoes an alternate source of blood, mosquitoes in Africa were much more aggressive against humans. All four types of malaria were present in Africa, but P. falciparum was far more prevalent in Africa than in other regions of the world, just as it is today. Eventually, the local populations began to develop genetic mutations in the form of Duffy negative red blood cells (offering almost completely protection from P. vivax) and hemoglobin S (offering protection against P. falciparum). As populations began to spread, so did malaria. Malaria moved from sub-Saharan Africa, to North Africa, to the Mediterranean region, to mainland Europe, and eventually became a scourge in areas as far north as the marshes of England. Europeans began transporting slaves from Africa to North and South America and with them came malaria. Malaria was also transported to the United States by settlers from the Fen region of England. In the United States, malaria became a very deadly problem. In some regions of the eastern coast of the United States, malaria was so prevalent and deadly that the majority of male children were not expected to live past age 5 and those who did were lucky to survive past age 20.
Eventually through social and economic advancements, changes in agricultural patterns, and the development of the first effective treatment for P. falciparum malaria, quinine, the prevalence of malaria in the developed world decreased to manageable levels. However, while malaria decreased in prevalence in the developed world, changes in the emerging worlds of Africa and Southeast Asia allowed malaria to spread. Natural defenses against malaria were diminshed. Dams were built, creating breeding pools for mosquitoes, populations were moved and were exposed to types of malaria they were not resistant to, and malaria became more prevalent. What is Being Done Today
Today, malaria is still a huge problem and unfortunately, will most likely never be eradicated. However, that does not mean that steps should not be taken to reverse the spread of the disease. In 1972, Artemisinin, a drug used against P. falciparum malaria, was developed to replace quinine, which many strains of malaria have developed a resistance to. Vector controls have been put in place to reduce the breeding abilities of the mosquitoes that carry Plasmodium parasites. These controls include the use of oils to cover the surface of ponds and mosquitofish, a type of minnow that feed primarily on mosquito larvae. Of course, these controls are not 100% effective, and mosquitoes will always find areas to breed in, which is why the world will always need mosquito netting.
While the eradication of mosquito-borne illnesses would put us out of business, we see more importance in the well-being of others than in the change in our pockets, so we will continue to make every effort possible to lessen the prevalence of mosquito-borne illnesses in the hope that one day, people all around the world will be able to truly enjoy their lives without having to worry about malarial infection.
Let us take this day to remember the millions of victims of malaria and to use this day to make others aware about the issue of malaria and mosquito-borne illnesses.
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