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Nasty Infectious Diseases You Want To Avoid - Malaria

Updated on December 31, 2008

This is an infectious disease caused by a parasitic protozoa within the red blood cells, now believed to be one of the major reemerging infections of the world. It is so serious that every 30 seconds somewhere in the world a child dies of the disease.

Malaria is one of the oldest known infections. First mentioned in ancient Sanskrit and Chinese documents, malaria was described in detail by Hippocrates who discriminated among different types of malarial fever in the fifth century B.C.; early physicians thought the illness was carried by hot, wet air, which is where it got its name-from the Italian word for "bad air." Long the scourge of the ancient world, it is believed that the army of Alexander the Great was probably wiped out by malaria during its march across India.

Among Africans, it is believed that the neverending pressure of the illness led to the rise of the sickle-cell trait common in that population. The slight deformity of the red blood cells in sickle cell anemia discourages the infiltration by the malarial parasite.

It is believed that malaria was introduced into the United States by European colonists and African slaves in the 16th and 17th centuries, where it then became endemic in many areas of the country, following the migration of the colonists. It was a particular problem in warm, wet areas of the United States such as the Chesapeake Bay region and the Mississippi Valley. It is believed that Andrew Jackson, Ulysses S. Grant, and George Washington all at various times suffered from malaria.

The first treatment against the disease was begun as early as 1630, when "Jesuit's bark" (the bark of the chinchona tree) was used to ease the fever of a Spanish magistrate in Peru. News of the treatment spread to Europe, where chinchona bark cure was enthusiastically adopted-except by the profoundly antiCatholic Oliver Cromwell, who refused to take Jesuit's bark for malaria and died of the disease. Eventually, quinine was isolated from the bark, leading to the development of the synthetic version (chloroquine). This cheap, effective drug almost won the world's battle with malaria until resistant strains of the disease began appearing in the 1960s.

The incidence of the disease peaked in 1875, but it is estimated that more than 600,000 cases were reported in 1914. By 1934, the number of cases dropped to 125,556, and by the 1950s, experts concluded that malaria had been eliminated in this country, through the efforts of spraying, removing breeding sites, accurate assessment, and focused control. It was still understood that international travel could reintroduce the disease into this country. Since 1957, nearly all cases diagnosed in the United States have been acquired by mosquito transmission in areas where malaria is known to exist. About half the cases occur among native U.S. citizens, and half occur in foreign-born people.

Environmental changes, the spread of drug resistance, and increased air travel could lead to the reemergence of malaria as a serious public health problem in the United States, according to the U.S. Centers for Disease Control and Prevention. Recent outbreaks of mosquito transmitted diseases in densely populated areas of New Jersey, New York, Texas, and Michigan are evidence that the risk exists.

Indeed, the parasite that causes malaria has become resistant to the usual antimalarial drugs. Only 10 percent of the world's population was at risk of catching this disease in 1960, but today that number has grown to 40 percent. The number of deaths worldwide is very high, ranging from 1.4 million to 2.4 million a year, according to the World Health Organization. Most of the deaths occur in children under age five, and most occur in Africa.

Cause - Malaria is caused by four different species of the Plasmodium parasite transmitted by the Anopheles mosquito. The deadliest parasite causing the sometimes-fatal version of malaria is Plasmodium falciparum; others are P. vivas, P. malariae, and P. ovale. Parasites in the blood of an infected person are taken into the stomach of the mosquito as it feeds; when the mosquito bites a person, parasites are injected into the person's bloodstream, migrating to the liver and other organs. After an incubation period from 12 days to 10 months (depending on the variety), parasites return to the bloodstream and invade the red blood cells. At this point, symptoms appear. Rapid multiplication of the parasites destroys the red cells and releases more parasites capable of infecting other red blood cells. This leads to the shivering, fever, and sweating that is the hallmark of the disease; the loss of healthy red cells causes anemia. The mature parasites remain in the blood and don't reinvade the liver, although a few may remain behind in the liver in a dormant state. These can be released months or years later, causing a relapse of malaria in people who thought they were cured.

Symptoms - Symptoms vary and may appear from 8 to 12 days after a bite in falciparum malaria to as many as 30 days for other types. Early signs may mimic the flu, causing fever, chills, headache, muscle ache, and malaise. As each new batch of parasites is released, symptoms of shivering and fever reappear. The interval between fever attacks is different in different types of malaria; in quartan malaria caused by P. malariae it is three days; in tertian malaria (P. ovale or P. vivax) it is two days; in malignant tertian (or quotidian) malaria (P. falciparum)-the most severe kind-from a few hours to a few days. In the most serious form of malaria (falciparum malaria), red blood cells become sticky and block the small blood vessels to the brain, kidney, and lungs, damaging these organs. Patients with this variety can die within several days without antibiotics. Irreversible complications can come on suddenly. Malaria is more severe in children; more than 10 percent of untreated children will die. If infection occurs during pregnancy, there is a risk of premature delivery, abortion, and stillbirth. Anyone who becomes ill with chills and fever after being in an area where malaria is endemic must see a doctor. Delaying treatment of falciparum malaria can be fatal. Because malaria is often misdiagnosed by North American doctors, travelers to malaria-ridden areas must be tested with a specific blood test for malaria, which requires direct microscopic exam of red blood cells to look for the parasite.

Diagnosis - Blood smears are necessary for a diagnosis; the parasite can be specifically identified on blood smears on slides. Antibody tests are not always helpful because many people have antibodies from past infections.

Treatment - People who become ill with fever during or after being in a high-risk area should seek prompt medical attention. Malaria can be treated effectively in the early stages, but delaying treatment can have serious consequences. Effective drugs include chloroquine, quinacrine, and chloroguanide. More recently, scientists in China discovered a drug called artemether (derived from a Chinese herb qinghaosu) appears to be as effective as quinine in preventing malarial deaths. The need for a different drug is imperative, since the parasite is becoming resistant to quinine and chloroquine. There are side effects with both the standard and the newer treatment. Quinine increases the risk of low blood sugar and abscesses at the injection site. Patients treated with artemether are slower to come out of their malaria-induced coma, and more likely to have convulsions. Other animal studies suggest brain stem damage is related to high doses of artemether. Falciparum malaria requires hospitalization, with IV fluids, red blood cell transfusions, kidney dialysis (if kidneys fail), and assisted breathing.

Prevention - The World Health Organization has been trying to eradicate malaria for the past 40 years by killing mosquitoes that carry the parasite, but as the mosquitoes and parasites became resistant to insecticides, prevention now aims at avoiding bites and taking preventive medicine (such as mefloquine or lariam). Malaria can often be prevented by the use of antimalarial drugs and use of personal protection measures against mosquito bites. While the risk of malaria is slight in the United States, people traveling to high-risk areas should take precautions. The risk for tourists who stay in air-conditioned hotels on tourist trips in urban or resort areas is lower than that for backpackers, missionaries, and Peace Corps volunteers. Decisions on whether to use antimalarial drugs depends on the traveler's itinerary, duration of travel, and the place where the traveler will spend each night.


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