Malaria

Key Features

Essentials of Diagnosis

• Exposure to anopheline mosquitoes in a malaria-endemic area

• Intermittent attacks of chills, fever, and sweating

• Headache, myalgia, vomiting, splenomegaly; anemia, thrombocytopenia

• Intraerythrocytic parasites identified in thick or thin blood smears or positive rapid diagnostic tests

• Complications of falciparum malaria, including

  • Cerebral malaria

  • Severe anemia

  • Hypotension

  • Noncardiogenic pulmonary edema

  • Acute kidney injury

  • Hypoglycemia

  • Acidosis

  • Hemolysis

General Considerations

• Five species of the genus Plasmodium are responsible for human malaria

  • P vivax

  • P malariae

  • P ovale

  • P falciparum

  • P knowlesi

• Mode of transmission

  • Bite of infected female anopheline mosquitoes

  • Can be transmitted congenitally and by blood transfusion (uncommon)

• P falciparum is responsible for nearly all severe disease because it

  • Uniquely infects erythrocytes of all ages

  • Mediates the sequestration of infected erythrocytes in small blood vessels, thereby evading clearance by the spleen

• P vivax seldom causes severe disease

• P ovale and P malariae generally do not cause severe illness

• For all plasmodial species, parasites may recrudesce following initial clinical improvement after suboptimal therapy

• Disease and response to therapy are dramatically affected by immune status

• P knowlesi, a parasite of macaque monkeys, causes illnesses in humans, including some severe disease, in Southeast Asia

Demographics

• Causes hundreds of millions of cases and hundreds of thousands of deaths each year

• Disease is endemic in most of the tropics, including

  • Central and South America

  • Africa

  • The Middle East

  • The Indian subcontinent

  • Southeast Asia

  • Oceania

• Transmission, morbidity, and mortality are greatest in Africa

• Disease also common in travelers from nonendemic areas

• Groups at particular risk for severe malaria

  • Children

  • Pregnant women

  • HIV-infected persons

  • Nonimmune travelers

Clinical Findings

Symptoms and Signs

ACUTE MALARIA

• Typically begins with a prodrome of headache and fatigue, followed by fever (usually irregular)

• Without therapy, however, fevers may become regular, especially with non-falciparum disease

  • 48-hour cycles (for P vivax and P ovale)

  • 72-hour cycles (for P malariae)

• Headache, malaise

• Myalgias, arthralgias

• Cough

• Chest pain, abdominal pain

• Anorexia, nausea, vomiting, and diarrhea

• Seizures may represent simple febrile convulsions or evidence of severe neurologic disease

• Physical findings may be absent or include signs of

  • Anemia

  • Jaundice

  • Splenomegaly

  • Mild hepatomegaly

SEVERE MALARIA

• Characterized by signs of severe illness, organ dysfunction, or a high parasite load (peripheral parasitemia > 5% or > 200,000 parasites/mcL)

• Principally a result of P falciparum infection

• Can include dysfunction of any system, including

  • Neurologic abnormalities progressing to alterations in consciousness, repeated seizures, and coma (cerebral malaria)

  • Severe anemia

  • Hypotension and shock

  • Noncardiogenic pulmonary edema and the acute respiratory distress syndrome

  • Acute kidney injury (due to acute tubular necrosis or, less commonly, severe hemolysis)

  • Hypoglycemia

  • Acidosis

  • Hemolysis with jaundice

  • Hepatic dysfunction

  • Retinal hemorrhages and ...