Malaria is a parasitic disease that involves high fevers, shaking chills, flu-like symptoms, and anemia.
Quartan malaria; Falciparum malaria; Biduoterian fever; Blackwater fever; Tertian malaria; Plasmodium
Causes, incidence, and risk factors
Malaria is caused by a parasite that is transmitted from one human to another by the bite of infected Anopheles mosquitoes. In humans, the parasites (called sporozoites) travel to the liver, where they mature and release another form, the merozoites. These enter the bloodstream and infect the red blood cells.
The parasites multiply inside the red blood cells, which then rupture within 48 to 72 hours, infecting more red blood cells. The first symptoms usually occur 10 days to 4 weeks after infection, though they can appear as early as 8 days or as long as a year after infection. Then the symptoms occur in cycles of 48 to 72 hours.
The majority of symptoms are caused by the massive release of merozoites into the bloodstream, the anemia resulting from the destruction of the red blood cells, and the problems caused by large amounts of free hemoglobin released into circulation after red blood cells rupture.
Malaria can also be transmitted from a mother to her unborn baby (congenitally) and by blood transfusions. Malaria can be carried by mosquitoes in temperate climates, but the parasite disappears over the winter.
The disease is a major health problem in much of the tropics and subtropics. The CDC estimates that there are 300-500 million cases of malaria each year, and more than 1 million people die. It presents a major disease hazard for travelers to warm climates.
In some areas of the world, mosquitoes that carry malaria have developed resistance to insecticides. In addition, the parasites have developed resistance to some antibiotics. This has led to difficulty in controlling both the rate of infection and spread of this disease.
Falciparum malaria, one of four different types of malaria, affects a greater proportion of the red blood cells than the other types and is much more serious. It can be fatal within a few hours of the first symptoms.
Signs and tests
Malaria, especially Falciparum malaria, is a medical emergency requiring hospitalization. Chloroquine is a frequently used anti-malarial medication, but quinidine or quinine plus doxycycline, tetracycline, or clindamycin; or atovaquone plus proguanil (Malarone); or mefloquine or artesunate; or the combination of pyrimethamine and sulfadoxine, are given for chloroquine-resistant infections. The choice of medication depends in part on where you were when you were infected.
Aggressive supportive medical care, including intravenous (IV) fluids and other medications and breathing (respiratory) support may be needed.
The outcome is expected to be good in most cases of malaria with treatment, but poor in Falciparum infection with complications.
Calling your health care provider
Call your health care provider if you develop fever and headache after visiting the tropics.
Most people living in areas where malaria is common have acquired some immunity to the disease. Visitors will not have immunity, and should take preventive medications. It is important to see your health care provider well before your trip, because treatment may begin is long as 2 weeks before travel to the area, and continue for a month after you leave the area. The types of anti-malarial medications prescribed will depend on the area you visit. According to the CDC, travelers to South America, Africa, the Indian subcontinent, Asia, and the South Pacific should take one of the following drugs: mefloquine, doxycycline, choroquine, hydroxychoroquine, or Malarone.
Even pregnant women should take preventive medications because the risk to the fetus from the medication is less than the risk of acquiring a congenital infection.
People on anti-malarial medications may still become infected. Avoid mosquito bites by wearing protective clothing over the arms and legs, using screens on windows, and using insect repellent.
Chloroquine has been the drug of choice for protection from malaria. But because of resistance, it is now only suggested for use in areas where Plasmodium vivax, P. oval, and P. malariae are present. Falciparum malaria is becoming increasingly resistant to anti-malarial medications.
For travelers going to areas where Falciparum malaria is known to occur, there are several options for malaria prevention, including mefloquine, atovaquone/Proguanil (Malarone), and doxycycline.
Travelers can call the CDC for information on types of malaria in a given geographical area, preventive drugs, and times of the year to avoid travel. See: www.cdc.gov
ReferencesKrogstad DJ. Malaria. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier. 2007: chap 366.
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.