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Disease: Malaria Malaria
Category: Infectious diseases

Disease Definition:

Malaria is an infectious disease that is caused by a parasite that is transmitted by mosquitoes. Recurrent attacks of chills and fever may be caused by malaria, which can be fatal.


Malaria is still prevalent in tropical and subtropical countries in Africa, Asia, the Middle East, South America and Central America; however, it has been virtually eradicated in countries with temperate climates. Malaria remains one of the world's leading infectious killers, particularly of children in sub-Saharan Africa.


One should take precautions before traveling to malaria-endemic places. Antimalarial drugs are used to treat this disease. 

Work Group:

Symptoms, Causes


The characteristics of malaria include recurrent attacks with the following signs and symptoms:


  • High fever
  • Malaise, which is a general feeling of discomfort and unease
  • Moderate to severe shaking chills
  • Profuse sweating as body temperature falls


Some of the other signs and symptoms of malaria may be:


  • Diarrhea
  • Nausea
  • Headache
  • Vomiting


People should be cautious if they develop an illness with fever while living in a malaria-endemic area or within 12 months after traveling to a high-risk malaria region because malaria infection initially appears to be a flu-like illness or some other viral disease. In this case, the patient should see a doctor as soon as possible and tell where he/she has traveled. A malaria infection can cause serious, potentially life-threatening health problems in case it is left untreated.


Malaria becomes a global health problem by evolving strains of drug-resistant parasites and insecticide-resistant mosquitoes.


What causes malaria is a one-celled parasite called plasmodium. There are about 170 species of plasmodium, but only four of those species cause malaria in humans; those are:

P. ovale:

This species is found mostly in West Africa. It can remain in the liver and cause relapses for up to four years, but it is rare. 

P. vivax:

This species, found mostly in tropical areas of Asia, produces less severe symptoms but can remain in the liver and cause relapses for up to four years.

P. falciparum:

This species, which is predominant in Africa, is responsible for most malaria deaths and produces the most severe symptoms.

P. malariae:

This species, which is found in Africa, can cause typical malaria symptoms, but on rare occasions, it can remain in the bloodstream for years without producing symptoms. In these cases, a person may pass on the parasite to a mosquito or to another person through a blood transfusion.



A female anopheles mosquito is the transmitter (vector) of the plasmodium parasite to humans. A mosquito ingests a form of the parasite called gametocytes when it bites a person infected with malaria. Inside the mosquito, the plasmodium completes part of its life cycle, making its way to the mosquito's salivary glands. Then, the mosquito injects the parasite into the bloodstream of a person when it bites him/her.


The parasite migrates rapidly to the liver where it infects certain liver cells and develops for a week or so. Releasing a multiplied form of the infection into the bloodstream, the liver cells eventually burst. Once in the red blood cells, the parasites reproduce further and some develop into the form that's available to be ingested by a mosquito (gametocytes), thus renewing the transmission cycle. A form of the parasite can remain inactive in the liver for extended periods of time in some cases of P. vivax or P. ovale infection. A relapse is caused by a reactivation of the parasite's life cycle later on.



The infection can be transmitted by a pregnant woman to her unborn baby. Blood transfusions can also transmit malaria. To prevent this type of transmission, steps have been taken such as prohibiting people who have been in a malaria-endemic area from donating blood for a year after returning from such an area, or three years if they've been a resident of a malaria-endemic area or have been treated for malaria.


The risk for serious illness is at the highest level in people who have little or no immunity to malaria. During their lifetime, residents of a malaria region may acquire some immunity to the disease; however, those who haven't yet acquired immunity are at risk. People who are at increased risk for serious disease include:


  • Pregnant women and their unborn children
  • Young children and infants
  • Travelers coming from areas with no malaria


Worldwide, malaria deaths can be contributed to by little or no access to health care, lack of knowledge and poverty.
If one is no longer frequently exposed to the parasite, it's also possible to lose his/her immunity. So, people should take antimalarial precautions if they return to such an area after an extended period away, even if they have previously lived in a region where malaria exists.



An infection with P. falciparum causes the most serious complications of malaria, such as: 

Cerebral malaria:

Swelling of the brain or brain damage may occur if parasite-filled blood cells block small blood vessels to the brain.


Extensive destruction of red blood cells may cause anemia.


Some of the other complications that malaria may cause include:


  • Kidney failure
  • Liver failure
  • Breathing problems, at times severe in the form of accumulated fluid in the lungs (pulmonary edema)
  • Enlarged spleen
  • Dehydration


P. falciparum malaria can be fatal within a matter of hours if left untreated.



Prompt evaluation and treatment are required in a malaria infection, particularly with P. falciparum. With one or more of the following medications, malaria can be effectively treated in most cases:


  • Quinine sulfate 
  • Doxycycline
  • Chloroquine
  • Mefloquine
  • Hydroxychloroquine 
  • A combination of sulfadoxine and pyrimethamine
  • A combination of atovaquone and proguanil 
  • Halofantrine: Because it can be dangerous and possibly fatal, people shouldn't take halofantrine if they have been taking mefloquine for prevention of malaria or if they have heart problems.
  • Primaquine: To fight the dormant liver form of the parasite and prevent relapses, this drug may be used. However, the CDC has warned against taking primaquine if one is pregnant or has an enzyme deficiency called glucose-6-phosphate dehydrogenase (G6PD) efficiency. A person shouldn’t be given primaquine until he/she has been tested for the deficiency mentioned above.
  • Artemisinin-derived medications: Another class of antimalarial drugs often prescribed in Asia and now in other parts of the world; it is derived from artemisinin, a sweet wormwood extract. One example of an artemisinin derivative is artesunate.


The length of treatment and which drug one should take depend on how sick the person was when the treatment began, the age of the patient, where was he/she infected and the type of malaria. Depending on the severity of illness, drugs are given either intravenously or orally. They may be given in suppository form in some countries. The patient may feel very weak and tired for a few weeks after treatment.

The problem of drug resistance:

A constant struggle between the search for new drug formulations and evolving drug-resistant parasites has marked the history of antimalarial medicine. Resistance to chloroquine has rendered the drug ineffective for instance in many parts of the world. Therapies that combine artemisinin derivatives with other companion drugs are currently being focused on by anti-malaria experts. Artemisinin-based combination therapy (ACT) is what these combinations are called. Acting quickly in the bloodstream, artemisinins help the patient feel better faster and clear away the parasites rapidly. By reducing the number of gametocytes — the infective version of the parasite — in the bloodstream, they may also help reduce transmission of the disease.  ACT has few known side effects. There's little documented resistance to artemisinins, and their combination with other drugs may slow resistance to these companion drugs as well.


The bad thing about these combination drugs is that they are more expensive than the conventional antimalarials. In order to avoid administering drugs for which resistance is already present and so weaken the effect of the combination therapy, doctors must be careful in selecting companion drugs for different geographical regions.


To find companion drugs that haven't already been used as antimalarials is one of the goals of malaria research, and as a consequence, lessening the risk of drug resistance. To prove the safety and effectiveness of combination therapies, particularly with regard to children and pregnant women, more research is needed.


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