Malaria

Definition

Malaria is a blood-borne disease caused by a parasite. The parasite is typically transmitted to humans via the bite of an infected mosquito, though blood transfusions from an infected person can also rarely be a source.

Causes

Malaria is caused by one of the following four types of parasites:

  • Plasmodium falciparum
  • Plasmodium vivax
  • Plasmodium ovale
  • Plasmodium malariae

When a female Anopheles mosquito bites someone infected with malaria, the mosquito becomes infected with the parasite. After a two-week period during which the parasite undergoes transformation and multiplication within the mosquito’s body, another bite will transfer malaria into a new person's bloodstream.

Once inside the human bloodstream, parasites travel to the liver and multiply (hepatic phase). During this phase, the infected person has no symptoms. After several days, the parasites' offspring are released into the bloodstream, where they infect red blood cells. Within 48 hours, the infected red blood cells burst and the parasites infect more red blood cells. This process leads to the chills, fever, and other symptoms that are typical of malaria. Without treatment, the cycle of red blood cell destruction and fever will continue and may lead to death. Plasmodium falciparum is by far the most dangerous of the forms of malaria and, unfortunately, in most areas it is also the most common.

Malaria can also be transmitted from a mother to her unborn child or from a transfusion of blood from an infected donor.

Malaria Cycle

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Risk Factors

A risk factor is something that increases your chance of getting a disease or condition. Risk factors include:

  • Living in or traveling to hot, humid climates where Anopheles mosquitoes are prevalent
  • Failing to use DEET-containing insect repellents when outdoors
  • Failing to use mosquito netting (especially netting treated with permethrin) while sleeping
  • Failing to use medications to prevent malaria infection
  • Geography: Africa, Asia, and Latin America; while deaths from malaria occur regularly among tourists who fail to follow recommended precautions, the majority of fatal cases of malaria seem to be acquired by tourists visiting game parks and other rural areas in east Africa.

Symptoms

A person infected with malaria will experience some or all of the following symptoms:

  • Recurrent fevers (as high as 106 degrees F)
  • Chills
  • Diffuse muscles aches
  • Headaches
  • Nausea and/or vomiting
  • Diarrhea
  • Anemia
  • Jaundice (yellow coloring of the skin or eyes)

Symptoms usually begin within 10 days to four weeks after being bitten by an infected mosquito. However, P malariae may not produce symptoms for a year or more. P falciparum infections tend to cause more severe symptoms and are associated with higher death rates.

Diagnosis

The doctor will ask about your symptoms, medical history, and travel history. The doctor will also perform a physical exam. You will have a blood test to analyze your blood for parasites.

Treatment

Malaria is treated with prescription drugs to kill the parasites. Choice of antimalarial agent depends on the type of parasite, and the severity and stage of infection. In many parts of the world, P falciparum is resistant to chloroquine, the main malaria treatment.

The following medications are used alone or in combination:

  • Chloroquine
  • Mefloquine (Lariam)*
  • Doxycycline*
  • Clindamycin*
  • Malarone*
  • Quinidine*
  • Quinine*
  • Combination of pyrimethamine and sulfadoxine (Fansidar)*
  • Primaquine (for hepatic phase of P vivax and P ovale )
  • Artemisinin*

*Commonly used to treat chloroquine-resistant strains of P falciparum .

Prevention

To reduce your chance of getting malaria when in an area where malaria is prevalent:

  • Take antimalaria medication prior to, during, and after travel. Follow your doctor's instructions and take medication exactly as prescribed.
  • Use DEET insect repellent (at least 30%-35%) when outside.
  • Use proper mosquito netting at night.
  • Use flying insect spray in non air-conditioned rooms while sleeping.
  • Wear clothing that covers as much skin as possible.
  • Avoid being outdoors from dusk to dawn, when Anopheline mosquitoes are especially prevalent.
  • Even if taking all precautions appropriately (including antimalaria medication) seek medical care immediately for any illness associated with high fever.

RESOURCES:

Centers for Disease Control
http://www.cdc.gov

World Health Organization
http://www.who.org

CANADIAN RESOURCES:

BC HealthGuide
http://www.bchealthguide.org

Public Health Agency of Canada
http://www.phac-aspc.gc.ca

References:

Navy Medical Department Pocket Guide to Malaria Prevention and Control . Bureau of Medicine and Surgery; 1998.



Last reviewed October 2007 by David Horn, MD, FACP

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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