Description

• Potentially deadly infection with Plasmodium species protozoa, transmitted to humans by Anopheles mosquitoes
• System(s) affected: cardiovascular, hematologic, renal, respiratory, cerebral, lymphatic, immunologic, hepatic

Epidemiology

• Cases imported to the United States: 79% Plasmodium falciparum; 11% Plasmodium vivax; 6% Plasmodium ovale; 3% Plasmodium malariae
• About 229 million cases annually worldwide; with ~400,000 deaths/year (primarily children in sub-Saharan Africa)
• Most prevalent in rural tropics

Incidence
~2,000 cases (>99% are imported) and 7 deaths per year in the United States

Prevalence

• Predominant age: all ages
• Predominant sex: male = female

Etiology and Pathophysiology

• Plasmodia are transmitted via saliva from an infected Anopheles mosquito to the human during a blood meal. Circulating plasmodia enter red blood cells (RBC), digest RBC proteins and alter the RBC membrane, causing hemolysis, increased splenic clearance, and anemia.
• RBC lysis stimulates release of cytokines and TNF-α causing fever and systemic symptoms.
• P. falciparum alters RBC viscosity, causing obstruction and end-organ ischemia.

Genetics
Inherited conditions may affect disease severity and susceptibility (e.g., sickle cell disease or trait)

Risk Factors

• Travel to or migration from endemic areas
• In nonendemic areas, rarely: blood transfusion, congenital transmission, and autochthonous transmission

General Prevention

• Mosquito avoidance: Use insect repellent, wear clothing to cover exposed skin, use mosquito nets treated with insecticides such as permethrin, and avoid outdoor activity from dusk to dawn, when feeding activity of Anopheles mosquito is the greatest.
• Malarial chemoprophylaxis in endemic areas
  • Atovaquone/proguanil: Begin 1 to 2 days before arrival, take daily until 1 week after leaving area. Adults, 1 adult tablet QD; children 5 to 8 kg, 1/2 pediatric tablet QD; children 9 to 10 kg, 3/4 pediatric tablet QD; children >10 to 20 kg, 1 pediatric tablet QD; children >20 to 30 kg, 2 pediatric tablets QD; children >30 to 40 kg, 3 pediatric tablets QD; children >40 kg, 1 adult tablet QD
    • Contraindicated in pregnant women and infants <5 kg
  • Chloroquine: Begin 1 to 2 weeks before arrival, take weekly until 4 weeks after leaving area. Adults, 500-mg salt (300-mg base) weekly; children, 8.3 mg/kg salt (5-mg base/kg) weekly up to 500-mg salt
    • Caution: can make psoriasis worse
  • Doxycycline: Begin 1 to 2 d before arrival, take daily until 4 weeks after leaving area. Adults, 100 mg QD; children >8 years old, 2 mg/kg up to 100 mg QD
    • Caution: Don’t use in pregnant women and children ≤8 years old.
  • Hydroxychloroquine: Begin 1 to 2 weeks before arrival, take weekly until 4 weeks after leaving area. Adults, 400-mg salt (310-mg base)/week; children, 6.5 mg/kg salt (5-mg base/kg)/week up to 400-mg salt
  • Mefloquine: Begin at least 2 weeks before arrival, take weekly until 4 weeks after leaving area. Adults, 250 mg (1 tablet) weekly; children ≤9 kg, 5 mg/kg weekly; children >9 to 19 kg, 1/4 tablet weekly; children >19 to 30 kg, 1/2 tablet weekly; children >30 to 45 kg, 3/4 tablet weekly; children >45 kg, 1 tablet weekly
    • Caution: mefloquine-resistant areas; don’t use if history of psychiatric disorders.
  • Primaquine: Begin 1 to 2 d before arrival, take daily until 1 week after leaving area; adults, 30 mg QD; children, 0.5 mg/kg/day up to adult dose
    • Use only in areas endemic for P. vivax
    • Caution: Exclude G6PD deficiency prior to first use; don’t use in pregnant women or breastfeeding women if infant hasn’t been tested for G6PD deficiency.
  • Tafenoquine: Begin 3 days before arrival, take daily until 1 week after leaving area; adults 200 mg QD
    • Caution: Exclude G6PD deficiency prior to first use; don’t use if history of psychiatric disorders; don’t use in children or in pregnant or breastfeeding women.

Commonly Associated Conditions

• Bacterial coinfections sometimes occur.
• Sickle cell trait confers an element of protection.