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KEY POINTS

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  • Malaria should be excluded as a cause of fever in any febrile patient who has traveled recently to a malaria-endemic area, or who may have been infected by contaminated blood through transfusions, needlestick injury, or other methods of direct infection.

  • Immunity to malaria may be short lived, so that even those who have been brought up in malaria-endemic areas can develop severe disease when they return as travelers.

  • Severe malaria is a medical emergency and ideally should be managed by experienced personnel in an intensive care setting.

  • Although Plasmodium falciparum is the most important cause of serious malaria, P vivax and P knowlesi can also cause severe and fatal infections.

  • Intravenous artesunate should be given as soon as practicable and alternative or additional diagnoses should be excluded.

  • Complications of malaria such as hypoglycemia, lactic acidosis, seizures, organ failure, and secondary infections should be diagnosed early by regular monitoring and managed aggressively.

  • Malaria can be particularly severe in immunocompromised individuals including those who have been splenectomized.

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THE BIOLOGY OF MALARIAL PARASITES

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Since antiquity malaria has been a potent selective force on humanity’s history and its genes.1 Some Egyptian pharaohs carried malarial parasites2 and there are many descriptions of fevers in ancient cultures that are consistent with the diagnosis of malaria. Alphonse Laveran in Algiers in 1880 discovered that protozoan parasites cause malaria.3 Since then, four species of Plasmodium: P falciparum, P vivax, P malariae, and P ovale are established as causes of natural human malaria infections, with a fifth species, P knowlesi, usually infecting monkeys, emerging as an important human pathogen in some geographic areas4 (Fig. 78-1). All species of malarias are naturally transmitted to humans by female Anopheles mosquitoes when infected insects feed on blood. Annually, they account for an estimated 400 million episodes of malaria and 800,000 deaths.5 Deaths have been falling in recent years due to concerted efforts to control transmission of malaria, for example, by the use of insecticide treated bed nets, and the use of effective artemisinin combination therapies to treat clinical episodes. Most cases of severe malaria are attributed to infections with P falciparum although P vivax is increasingly recognized as causing severe morbidity in a minority of cases, as well as fatalities in some patients.6,7 P knowlesi can also cause severe disease and death.8 Mixed species infections are common in some areas.

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FIGURE 78-1

Asexual stage parasites of Plasmodium species causing disease in human. Falciparum malaria is responsible for most severe and cerebral malaria. (Used with permission of Dr. Kamolrat Silamut.)

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When infected mosquitoes bite humans (Fig. 78-2), needle-shaped sporozoite stages of infection (approximately half a dozen) are injected and migrate within an hour to the liver to begin a clinically silent stage ...

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