Malaria

Electron micrograph of a malaria sporozoite

Malaria is an infectious disease. It is caused by parasites. People catch malaria when the parasite enters the blood. A parasite is an organism that lives off of another organism called a host. A parasite takes from the host organism, but does not help it. Instead, it usually harms the host.

The parasite that causes malaria is a protozoan called Plasmodium. Protozoa are organisms with only one cell, but they are not bacteria. Bacteria are smaller and simpler than protozoa.

There are several species (kinds) of Plasmodium that cause malaria in people:

P. vivax and P. falciparum cause the most malaria in people. Falciparum malaria is the worst kind, and kills the most people.

People usually get malaria from the Anopheles mosquitoes. The Plasmodium goes into people by mosquitoes bites. The Plasmodium is in the mosquito's saliva. (Saliva is moisture, or spit, made in the mouth.) The mosquito's saliva carries the Plasmodium into the person. The person is then infected with Plasmodium. This makes the person have the disease malaria.

The kind of mosquito that carries malaria is the anopheles mosquito. Only the female mosquito gives people malaria, because only the female mosquito bites.

Some people do not get malaria from mosquitoes. A baby can get it while inside its mother. This is called maternal-fetal transmission. People can also get malaria from a blood transfusion. This is when someone gives blood to another person. Another way people can catch malaria is by using a needle that someone with the disease used before them.

How Plasmodium lives in people

When Plasmodium enter the blood, they are called sporozoites. Sporozoites go to the liver, where they make many more sporozoites. Then they change into a different form of Plasmodium. This form is the merozoite. The merozoites go into the red blood cells, then they make many more merozoites.

The merozoites break out of the red blood cells again and again. When they do this, the person gets very sick, and shows symptoms of malaria. This happens every few days, and is called a paroxysm.

P. vivax and P. ovale can live in the liver for a long time. A person can look well, but still have the Plasmodium in the liver. This is called a dormant phase. Weeks or months later, the Plasmodium can leave the liver to the blood, and the person will get sick again.

P. falciparum is the most dangerous type of malaria. It makes people sicker than those with other types of malaria, because there are more of them in the blood. Also, with falciparum malaria, the red blood cells are sticky. This makes the red blood cells block blood vessels. If blood vessels are blocked, this can hurt what the blood vessel brings blood to, and can hurt people's organs.

Who is affected by malaria

Pregnant women and children are hurt most by malaria. When they get malaria, they get sicker.

40% of people live in a place where there is malaria. Malaria is in these places:


Every year, 300 to 700 million people get malaria. It kills 1 million to 2 million people every year. The biggest problem is in Africa. 90% of the people who die from malaria are there. Most of the people who die from malaria are children. In Africa, 20% of children under five die from malaria. Even if children do not die, many have brain damage.

Most of these deaths could be stopped with medicine or with ways to stop mosquitoes. UNICEF says: the medicine that costs the most for malaria is only $2.40 to help one adult. But many of the places malaria may be found are in poor countries. These countries do not have enough money to stop the mosquitoes, or to give people medicine.

Symptoms of malaria

Symptoms are changes in someone's body that are signs for a disease. Most people who get malaria get symptoms 10–30 days after they get infected (the Plasmodium gets in their blood.) But some people can get symptoms after only a week, and some may be infected with malaria and not have symptoms for a year.

The most common symptom of malaria is fever, when the body temperature is high. The fever from malaria usually comes very suddenly. The people who have Malaria often feel like they had influenza.

Symptoms of malaria are:

Complications from malaria

Complications are problems that happen because of a disease.

Pregnant women and young children have more complications. People who get malaria for the first time have more complications. Falciparum malaria has the most complications.

Complications of malaria are:

How doctors tell if someone has malaria

In places where malaria is, there may not be good medical care. People may diagnose malaria just by people having symptoms. Diagnose means to learn if a person has a disease. Doctors diagnose people sometimes just by symptoms. This is called a clinical diagnosis. Doctors also use tests to see if people have a disease.

Giemsa stain shows malaria trophozoite in red blood cell

If a person has symptoms and is in a place where there is malaria, they might have malaria. To see if they have malaria, doctors may do a blood test. This test is called a Giemsa blood smear. Blood is put on a slide which is a thin piece of glass. The Giemsa stain is put on the slide. This stain helps doctors see the malaria. Then they look at the slide under a microscope. The Plasmodium is seen in the red blood cells.

Sometimes the blood smear will not show Plasmodium even if the person has malaria. This can be because the stain was not good. It can also be because the microscope was not good. Or it can be because the person looking in the microscope did not know what Plasmodium look like. But often it is because the number of malaria parasites present in the blood is so low that they are not present in the section of the blood that was looked at.

There are other tests to diagnose malaria. These are more expensive. People do not use them as much. Sometimes people test to see if the Plasmodium is resistant to medicines to treat malaria. Resistance means the medicine cannot hurt the Plasmodium. This means that taking the medicine will not cure someone with malaria, because it will not kill the Plasmodium.

How to treat malaria

People with different kinds of malaria need different medicines. The medicine that works for one kind of malaria may not for another kind. So it is very important to know which species of Plasmodium the person has.

If the species is not known, the person should be given medicine and care like they have falciparum malaria - the worst kind.

It is also important to know where the person got malaria. Plasmodium in some places are resistant to some medicines. So the medicines to treat malaria in Africa are different from the medicines to treat malaria from South America.

It is important for doctors to learn about malaria treatment. Resistance to medicines changes. Places where there was no resistance can get resistant malaria. So doctors need to know when this changes. If a doctor treats a person with malaria, he should know what places in the world have resistant malaria. If he has not treated a person in a long time, he should check before treating people.

Treatment of malaria other than falciparum

Everywhere except New Guinea, the treatment is the same. In New Guinea most P. vivax is resistant to chloroquine. It can be treated with quinine, but this medicine can make people sick. Everywhere else, non-falciparum malaria is treated with chloroquine.

Chloroquine kills the Plasmodium in the blood. But the Plasmodium in the liver is not killed by chloroquine. P. vivax and P. ovale both stay in the liver a long time. This is the dormant phase. Another medicine must be given with chloroquine for P. vivax and P. ovale. This is to kill the Plasmodium in the liver. If this other medicine is not given, malaria can come back after months. It can even come back five years later.

The medicine used to kill malaria in the liver is primaquine. In southeast Asia, some P. vivax is resistant to primaquine. Most other places, primaquine works very well.

Some people get very sick from primaquine. Some people do not make enough of an enzyme in the blood. This enzyme is called Glucose-6-Phosphate-Dehydrogenase (Acronym G6PD). People who do not have enough have a disease called G6PD deficiency (or favism). People with G6PD-deficiency get very very sick if they take primaquine. It makes their red blood cells all die. This can even kill them. So people have to be tested to see if they have G6PD-deficiency before they take primaquine.

Medicines to kill P. vivax and P. ovale in the liver are not safe for pregnant women. So a pregnant woman must usually take chloroquine until she has her baby.

Treatment of falciparum malaria

Falciparum is the worst kind of malaria. Most people who die from malaria have falciparum.

Many people with falciparum malaria must be treated in a hospital. People with falciparum malaria should be treated in a hospital if they are:

Even people who are treated with medicines at home should stay with the doctors for 8 hours. This is to make sure they do not get sicker. It also makes sure they can take the medicines by mouth.

Falciparum malaria also has more resistance to medicines. This makes it much harder to treat. Falciparum malaria is always treated with two or more medicines. Doctors choose the medicines by where in the world the person got malaria. Different places have P. falciparum that is resistant to different medicines.

The most important resistance is chloroquine-resistance. In some places in the world, P. falciparum is killed by chloroquine. In some places it is chloroquine-resistant. This means chloroquine does not kill it. In these places quinine can be used.

If people are very sick and cannot swallow medicines, they get intravenous (acronym IV) medicine. Intravenous means given into a vein. The IV medicine used for very bad chloroquine-resistant falciparum malaria is quinine. If people got malaria in a place with no chloroquine-resistance other medicines can be used. But sometimes doctors still use IV quinine. This is to be very certain they will kill the P. falciparum.

If the P. falciparum is not chloroquine-resistant people do not usually take quinine. This is because quinine can make people sick. If people get sick from quinine, it is called Cinchonism. Symptoms of cinchonism are:

Quinine is also taken by mouth.

How to prevent malaria

The best way to treat malaria is to not get it!

There are three ways to prevent malaria:

Control mosquitoes

Vector control is one way to stop malaria. Vector means an organism that carries an infectious disease to another organism. For malaria, the vector is the anopheles mosquito. It carries Plasmodium to people.

There are many ways to conduct a good vector control. The best ways are different in different places. This depends on the environment. It also depends on how much malaria is in the place. So the best way to do vector control in the United States is different than the best way to do vector control in South Africa.

The most used method of vector control is pesticides. These are chemicals that kill the mosquito. The first pesticide used for vector control was DDT (dichlorodiphenyltrichloroethane.) DDT was first used in World War II.

DDT worked very well for vector control. It killed mosquitoes. It did not make people very sick at the time it was used. It did not cost very much money. Other chemicals for vector control had not been invented yet.

In many places mosquitos became resistant to DDT. This meant that DDT did not work anymore in these areas. The places where mosquitoes are DDT-resistant are:

The EPA (Environmental Protection Agency) classifies DDT as a Persistent Bioaccumulative Toxin (PBT)meaning that it builds up over time in the bodies of plants,animals and humans.DDT can be passed on from water to fish or some plants, and consequently passed from plant/fish on to humans who may eat them.

Possible Harmful Effects include:

Scientists also worried that DDT was making people and animals sick. Scientists think it might cause hormones to not work right. It might also make people and animals have trouble reproducing (getting pregnant and making babies.) It killed a lot of wildlife too.

They learned that DDT stays in the environment for a long time. They learned also that DDT used in one place may go all over the world. DDT used in Africa may go to Europe. So people are worried that DDT used today will stay in the world for a long time. This is why DDT is not allowed to be used in farming anymore.

For these reasons, people mostly use other chemicals for vector control. Organophosphate or carbamate pesticides are used, like malathion or bendiocarb. These cost more money than DDT. And there are ways to control malaria that do not use chemicals at all.

Vector control is not the only way to stop malaria. And DDT is not the only chemical that can be used for vector control. The best way to stop malaria is to use a combination of methods. In some places, DDT may be a useful part of a program to stop malaria. This is why DDT is still allowed to be used for controlling malaria.

Keeping mosquitoes from biting

The mosquito that carries malaria comes more at dawn (when the sun comes up) and dusk (when the sun goes down.) Be most careful at these times.

Wear long pants and shirts with long sleeves.

Wear mosquitoes repellent (this is a chemical that mosquitoes do not like, so they do not bite.) Mosquitoes will bite through thin cloth. So repellent should be used on skin and clothes.

Pesticides can be used in rooms to kill mosquitoes.

When sleeping outside, people use a mosquito net. This is made from cloth that air can go through but keeps mosquitoes out. It is put over a bed where people sleep to keep mosquitoes out. Sometimes people also use it when they are not sleeping. It is best to use mosquito nets that have been treated with Permethrin, which repels and kills mosquitoes.

Taking medicine to not get sick

People can take medicine when they are in a place where there is malaria. This reduces the chances that they contract malaria. This is called prophylaxis.

Some people take prophylactic medicines for years. Many people in areas where there is malaria do not have the money to buy this medicine.

People who live where there is no malaria usually have not had malaria. The first case malaria is usually much worse. So people from places where there is no malaria may take prophylactic medicines when they go to places where there is malaria.

The kind of prophylactic medicines people take depends on where they are. This is because not all medicines work on the malaria in every place. Some Plasmodium are resistant. Even if the right medicine is used, it does not always work. Sometimes people get malaria even if they take prophylaxis. Sometimes this is because people do not take the medicine the right way. But even if it is taken right, it does not always work.

To make them work best, prophylactic medicines have to be taken the right way. The medicine should start before going to an area with malaria. Most medicines should be taken for 4 weeks after coming home. One medicine (Malarone) only needs to be used for one week after coming home.

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