The term malaria originates from the Italian word mal'aria, meaning "bad air." The Romans knew about malaria 2,000 years ago. They believed that malaria was caused by foul air that resulted from fermentation that seeped out of marshes and swamps. There are various references to malaria-like diseases in the medical texts of many ancient civilizations. Apparently Babylonians, Egyptians, Indians, and Chinese all suffered from fatal fevers. Because it was generally believed that malaria was caused by some angry god or irritable divinity, the most popular cures included amulets and lucky charms, magic rituals, sacrifices, and special potions made from medicinal herbs (1). By 1000 BC, outbreaks of malaria were already common in Mediterranean countries such as Greece, Spain, and Italy. During the centuries that followed-known as the Dark Ages-much of the medical knowledge the Greeks and Romans had gained about malaria was forgotten. Malaria itself lost its identity and became confused with other run-of-the-mill types of feverish illnesses (1). In the meantime, as sanitation methods used by the Greeks and Romans were neglected, the disease continued to spread through Europe. By the sixth century, people were coming down with malaria in England, France, Holland, and even as far north as Scandinavia. By the twelfth century, malaria was common all over Europe (1).
When, on the heels of Columbus, the first Spanish conquistadors arrived in the New World, the disease tagged along with them and spread throughout the Americas. As the New World began to colonize, the disease spread rapidly. By the time of the Civil War (1861-1865), between 50 and 80 percent of the soldiers in the Union army came down with the disease each year. In fact, for a long time, malaria was endemic in areas such as the Mississippi Valley and around the Chesapeake Bay (1). Outbreaks of malaria continued in the United States well into the 1940s. In 1914 alone, there were over 600,000 cases of malaria recorded in the United States. Although today it is quite rare, there are nonetheless close to 1,200 Americans who are infected with malaria each year, most while traveling abroad. After years of decline, malaria is once again on the move. Despite the media attention given to AIDS and the H1N1 virus, malaria kills millions every year (1). It is a public health problem in about ninety countries worldwide. This puts 36 percent of the world's population at risk. According to estimates made by the World Health Organization (WHO), malaria infects about 400 million people each year, 90 percent of which live in Africa (1).
There are more than 50 species of Plasmodium, only four of which cause human malaria: Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale, and Plasmodium vivax. Plasmodium vivax is the most common. It usually causes a mild and very rarely fatal form of malaria (2). Similarly, Plasmodium ovale causes a mild infection. Plasmodium malariae causes a severe fever, but it is not usually life threatening. On the contrary, Plasmodium falciparum causes acute infection that kills millions every year. Plasmodium falciparum is the organism that causes the form of malaria that is typically thought of whenever the disease is mentioned (2). When an infected mosquito bites a person, the Plasmodium parasites enter the blood and head immediately for the liver. Within 30 minutes to one hour, all of the parasites have penetrated the liver; none remain in the circulating blood. Once inside the liver, the organisms multiply asexually, which means that each one divides into two identical copies of itself. They continue this reproduction in the liver cells for 9 to 16 days, after which they emerge from the liver and invade red blood cells (2). The parasites mature in the red blood cells, where they feed on hemoglobin and continue to reproduce asexually. If an Anopheles mosquito bites a person when the infected cells are present in the blood and picks up any of them, the malarial life cycle continues into its sexually reproducing generation. If a mosquito of a genus other than Anopheles bites someone with malaria, it simply digests any malarial cells that it swallows (2).
In the case of malaria, humans who are partially immune to the disease appear to be the reservoir host. Nonimmune humans act like the alternative hosts. The mosquito plays two roles. It is the vector, the means of transport from host to host. However, the parasite also needs the mosquito to complete its life cycle. That makes the mosquito a necessary part of the host-parasite cycle that is called the intermediate host. Because the malaria life cycle involves more than one host, Plasmodium is more complex than many other parasites. Whenever a parasite shows an alternation of generations in separate hosts, it reproduces sexually in only one of them. That host is known as the definite host. In the case of malaria, the definite host is the mosquito.
Mosquitoes are more likely to bite men than women, because mosquitoes are attracted to heat, and men give off more body heat than women do. This does not mean that mosquitoes will not bite women, however, including ones who are pregnant, and they will bite children as well, often preferentially because children radiate more heat than adults (3). Malaria can be very serious in children and pregnant women, and falciparum malaria may develop into cerebral malaria in children. When this happens, red blood cells containing the parasite become isolated in the child's brain to the point that blood vessels may be blocked. Death can result (3). Death can also result to a fetus of a pregnant woman or to the pregnant woman herself. In Africa, where the situation is extreme, there are many regions in which malaria is endemic. As a result of being bitten and infected continuously throughout their lives, many Africans build up immunity to the disease (3). This means that although the Plasmodium parasites might live within them throughout their lives, they will either suffer from mild symptoms form time to time or not experience any symptoms at all. Immunity to any disease often results from exposure to that disease. This applies to malaria but not perfectly. Human malarias appear to have evolved the ability to avoid the human immune system, and humans cannot develop a complete immunity to malaria as we can with, for example smallpox. It is possible, however, to develop a partial immunity to malaria. In this case, a survivor would remain infected with the parasites, but he or she would not show symptoms of the disease. Moreover, he or she could survive to reproduce and pass the immunity to a succeeding generation (3).
Before symptoms in someone infected with malaria begin to appear, there is an incubation period during which the parasites are quietly multiplying to levels where they begin to cause trouble (4). The incubation may be as short as a week, as is more often the case with Plasmodium falciparum, or as long as a month, which is more typical of the mild P.malariae. Once parasite levels in the blood are sufficiently high, symptoms begin to occur. The classic malaria cycle lasts for about six to ten hours (4). It usually begins with intense chills and shivering as the victim develops a fever. This is followed by a period of elevated temperature, headaches, vomiting, and in the case of young children, seizures. Finally, there is a period of fatigue and heavy perspiration as body temperature returns to normal. In the case of quartan malaria, caused by P. malariae, the cycle repeats every four days. It occurs every third day in the case of the other three (4).
The first treatment of malaria was with quinine, a compound isolated from the bark of the Cinchona tree of South America. Sometimes it is still the most effective treatment available. The first people to use Cinchona medically were the Indians of Peru, who used finely ground bark to treat fever (5). It was reasonable, therefore, for them to try to threat the fevers of malaria with ground cinchona bark. This treatment proved to be successful. Technically, quinine does not cure malaria because it does not kill all species of the parasite, but it kills enough of them to cure many people. In many parts of the world where the countries are poverty stricken, and the newer malarial drugs are ineffective or just not available, quinine is used to treat malaria. (5). Although quinine is given orally, in severe cases, where kidney failure or coma has occurred, it is given intravenously. The first synthetic antimalarial medication was developed in Germany during the 1930s. It was called Atabrine and it was used by the U.S. troops in World War II. More medications were developed during World War II. These include chloroquine, and doxycycline (1).
As Plasmodium parasites become increasingly resistant to traditional antimalarials, instead of upping the dosages-which proves expensive and can create serious side effects-researchers are looking for completely new alternatives (6). Derived from a family of plants known as artemisnins, Quinghaosu has been used medicinally to fight malarial fevers in China for over 2.000 years. Lately, the rest of the world has caught on, and tests have proved promising. Although not widely available, at this stage in the game artemisnins are the most effective antimalarials around, acting rapidly and with few side effects (6).
Fearing that sooner or later Plasmodium parasites will become resistant to artemisnins, many antimalarial campaigns have been directed at getting rid of anopheles. Although mosquito specialists now believe that wiping out mosquitoes isn't realistic, certain steps can be taken to put a severe damper on their human-chomping activities (7). DDT and other insecticides have proved problematic because not only do mosquitoes develop immunity to them, but the chemicals are environmentally unfriendly. So instead to chemical controls, scientists are currently looking at biological controls. Currently being explored are ways of getting other living organisms to eat or harm the mosquitoes before they eat or harm you (7). In the meantime, while all the great ideas are still in the developmental stages, health experts have come up with a much simpler, cheaper, and hands-on technique of keeping malaria at bay: using a mosquito net soaked in insecticide.
